Copyright: Microsoft Flight Simulator for Windows 98 Product Support


Accessibility for People with Disabilities
	Accessibility for People with Disabilities Microsoft is committed to making its products and services easier for everyone to use. This help file provides information about the following features, products and services, which make Microsoft® Windows® and Microsoft® Flight Simulator 98 more accessible for people with disabilities: NOTE: The information in this section applies only to users who purchased Windows in the United States If you purchased Windows outside the United States, your Windows package contains a subsidiary information card listing Microsoft support services telephone numbers and addresses You can contact your subsidiary to find out whether the type of products and services described in this help file are available in your area. Related Topics Microsoft Services for People Who are Deaf or Hard-of-Hearing Keyboard Layouts for Single-Handed Users Microsoft Documentation in Alternative Formats Third-Party Utilities To Enhance Accessibility More Information About Products and Services for People with Disabilities


Microsoft Services for People Who Are Deaf or Hard-of-Hearing
	Microsoft Services for People Who Are Deaf or Hard-of-Hearing Through a text telephone (TT/TDD) service, Microsoft provides people who are deaf or hard-of-hearing with complete access to Microsoft product and customer services. You can contact Microsoft Sales Information Center on a text telephone by dialing (800) 892-5234 between 6:30 A.M. and 5:30 P.M. Pacific time. For technical assistance you can contact Microsoft Support Network on a text telephone at (206) 635-4948 between 6:00 A.M. and 6:00 P.M. Pacific time, Monday through Friday, excluding holidays. In Canada, dial (905) 568-9641 between 8:00 A.M. and 8:00 P.M. Eastern time, Monday through Friday, excluding holidays. Microsoft support services are subject to Microsoft prices, terms, and conditions in place at the time the service is used. Related Topics Accessibility for People with Disabilities Keyboard Layouts for Single-Handed Users Microsoft Documentation in Alternative Formats Third-Party Utilities To Enhance Accessibility More Information About Products and Services for People with Disabilities


Keyboard Layouts for Single-Handed Users
	Keyboard Layouts for Single-Handed Users Microsoft distributes Dvorak keyboard layouts that make the most frequently typed characters on a keyboard more accessible to people who have difficulty using the standard "QWERTY" layout. There are three Dvorak layouts: one for two-handed users, one for people who type with their left hand only, and one for people who type with their right hand only. The left-handed or right-handed keyboard layouts can also be used by people who type with a single finger or a wand. You do not need to purchase any special equipment in order to use these features. Microsoft Windows and Microsoft Windows NT already support the two-handed Dvorak layout, which can be useful for coping with or avoiding types of repetitive-motion injuries associated with typing. To get this layout use the Windows Control Panel; consult your on-line documentation for detailed instructions. The two layouts for people who type with one hand are distributed as Microsoft Application Note GA0650. It is also contained in file GA0650.EXE on most network services and on the Microsoft Download Service. Related Topics Accessibility for People with Disabilities Microsoft Services for People Who are Deaf or Hard-of-Hearing Microsoft Documentation in Alternative Formats Third-Party Utilities To Enhance Accessibility More Information About Products and Services for People with Disabilities


Microsoft Documentation in Alternative Formats
	Microsoft Documentation in Alternative Formats People who have difficulty reading or handling printed documentation may obtain many Microsoft publications from Recording for the Blind, Inc Recording for the Blind distributes these documents to registered eligible members of their distribution service either on audio cassettes or on floppy disks. The Recording for the Blind collection contains more than 80,000 titles, including Microsoft product documentation and books from Microsoft Press You can contact Recording for the Blind at the following address or phone numbers for information on eligibility and availability of Microsoft product documentation and books from Microsoft Press:  Recording for the Blind, Inc. 20 Roszel Road Princeton, NJ  08540 Phone: (609) 452-0606 Fax: (609) 987-8116 Related Topics Accessibility for People with Disabilities Microsoft Services for People Who are Deaf or Hard-of-Hearing Keyboard Layouts for Single-Handed Users Third-Party Utilities To Enhance Accessibility More Information About Products and Services for People with Disabilities


Third-Party Utilities to Enhance Accessibility
	Third-Party Utilities to Enhance Accessibility A wide variety of third-party hardware and software products are available to make personal computers easier to use for people with disabilities. Among the different types of products available for the Microsoft® MS-DOS®, Microsoft Windows, and Microsoft Windows NT operating systems are: • Programs that enlarge or alter the color of information on the screen for people with visual impairments. • Programs that describe information on the screen in braille or synthesized speech for people who are blind or have difficulty reading. • Hardware and software utilities that modify the behavior of the mouse and keyboard. • Programs that enable users to “type” using a mouse or their voice. • Word or phrase prediction software that allows one to type more quickly and with fewer keystrokes. • Alternate input devices, such as single switch or puff-and-sip devices, for those who cannot use a mouse or a keyboard. Related Topics Accessibility for People with Disabilities Microsoft Services for People Who are Deaf or Hard-of-Hearing Keyboard Layouts for Single-Handed Users Microsoft Documentation in Alternative Formats More Information About Products and Services for People with Disabilities


More Information About Products and Services for People with Disabilities
	More Information About Products and Services for People with Disabilities For more information on Microsoft products and services for people with disabilities, contact:  Microsoft Sales Information Center One Microsoft Way Redmond, WA 98052-6393 Voice telephone: (800) 426-9400 Text telephone: (800) 892-5234 Fax: (206) 635-6100 The Trace R&D Center at the University of Wisconsin-Madison produces a book and a compact disc that describe products that help people with disabilities use computers. The book, titled Trace ResourceBook, provides descriptions and photographs of about 2,000 products. The compact disc, titled Co-Net CD, provides a database of more than 18,000 products and other information for people with disabilities. It is issued twice a year. To obtain these directories, contact: Trace R&D Center S-151 Waisman Center 1500 Highland Avenue Madison, WI 53705–2280 Voice telephone: (608) 263–2309 Text telephone: (608) 263–5408 Fax: (608) 262-8848 For general information and recommendations on how computers can help specific people, you should consult a trained evaluator who can best match your needs with the available solutions. An assistive technology program in your area will provide referrals to programs and services that are available to you. To locate the assistive technology program nearest you, you can contact: National Information System  Center for Developmental Disabilities Benson Building University of South Carolina Columbia, SC 29208 Voice/text telephone: (803) 777-4435 Fax: (803) 777-6058 Related Topics Accessibility for People with Disabilities Microsoft Services for People Who are Deaf or Hard-of-Hearing Keyboard Layouts for Single-Handed Users Microsoft Documentation in Alternative Formats Third-Party Utilities To Enhance Accessibility


When You Have a Question
	When You Have a Question If you have a question about Microsoft® Flight Simulator 98, first look in the online Help or consult the Pilot’s Handbook. You can also find late-breaking updates and technical information if there is a README file in the directory where you installed Flight Simulator. If you still have a question, Microsoft offers technical support and services ranging from self-help tools to direct assistance with a Microsoft technical engineer.  NOTE The services and prices listed here are available in the United States and Canada only. Support services may vary outside the U.S. and Canada. For more information on support in other locations, contact your local Microsoft subsidiary. Microsoft’s support services are subject to Microsoft’s then-current prices, terms, and conditions, which are subject to change without notice. Outside the U.S. and Canada, contact the local Microsoft subsidiary office in your area. For a list of Microsoft subsidiaries, click Microsoft Technical Support Worldwide. Related Topics Choose the Support Option That’s Right for You Self-Help Tools Online Other Self-Help Tools Direct Assistance from a Microsoft Technical Support Engineer Other Microsoft Services Microsoft Technical Support Worldwide


Choose the Support Option That's Right for You
	Choose the Support Option That’s Right for You Here are the options you can choose from: Self Help Tools Self-Help Tools Online Direct Assistance from a Microsoft Technical Support Engineer Direct Assistance from a Microsoft Technical Support Engineer Other Microsoft Services Includes information on customer service and text telephone numbers for the deaf. For more information, click: Other Microsoft Services Microsoft Technical Support Worldwide For information on how to obtain Microsoft Technical Support from Microsoft worldwide subsidiaries outside the U.S. and Canada, click: Microsoft Technical Support Worldwide


Self-Help Tools Online
	Self-Help Tools Online Microsoft Technical Support Online at http://www.microsoft.com/support/ This site uses the cutting-edge technology of Microsoft to help you access the most relevant technical information and resources to answer your support questions. Online support helps you find the answers you need quickly and easily through the following features: • Troubleshooting Wizards: Microsoft Technical Support Online has built-in diagnostic technology to help you easily pinpoint problems and identify solutions. Just ask for help on a specific problem, and a Troubleshooting Wizard will walk you through, step by step, until your question is resolved. Troubleshooting Wizards are like electronic versions of our own engineers. • Product-Specific Support Home Pages: Think of this as an electronic information synthesizer. It automatically pulls together the top technical articles, the most frequently asked questions, downloadable files, and more for your specific product. If you need an answer in a hurry, be sure to stop here first. Chances are the solution you are looking for is already waiting for you. • Frequently Asked Questions (FAQs): FAQs are questions about Microsoft products that our engineers have identified as those customers ask most often. Like the Product-Specific Support Home Pages, this invaluable feature extracts just the most critical, up-to-date questions and answers on your products to help you find solutions quickly. FAQs are updated continually. • Knowledge Base: Here you'll find a collection of more than 75,000 detailed articles—updated daily—with technical information about products, bug and fix lists, and answers to commonly asked technical questions. The Knowledge Base also provides descriptions of product issues and workarounds, optimization tips, and compatibility issues for every product. A step-by-step process helps you build a query to search the database, making it easy for you to look for information on the product or technology of your choice. • Help Files, Service Packs, & More: Keep your system current with access to thousands of files from our software library, all available for downloading. This includes free software add-ons (connect charges may apply), bug fixes, peripheral drivers, software updates, sample code, patches, application notes, sample files, and programming aids. • Support Site Tour: The Support Site Tour uses a "Support Wizard" to help you easily get the information most relevant to your product and technical support needs. First, select your product. Next, indicate what you would like to do: find a technical article, troubleshoot a problem, or download a driver. Then just double-click and the Support Wizard takes you where you want to go. • Newsgroups: This peer-to-peer communication forum links you to a worldwide community of other Microsoft customers and technical experts, including Microsoft's Most Valuable Professionals. Newsgroups offer a unique way to help you find answers, tips, and tricks by putting you in touch with other Microsoft product users who have similar interests. Related Topics When You Have a Question Choose the Support Option That’s Right for You Other Self-Help Tools Direct Assistance from a Microsoft Technical Support Engineer Other Microsoft Services Microsoft Technical Support Worldwide


Other Self-Help Tools
	Other Self-Help Tools In addition to the Internet resources, Microsoft Technical Support provides the following additional technical information resources: • Microsoft TechNet: If you are an information technology (IT) or Help desk professional responsible for administering your corporate network or supporting end users then you can stay on top of your organization's requirements with TechNet. TechNet is a comprehensive resource for evaluating, implementing, and supporting Microsoft business products. Every month, TechNet delivers two CDs packed with more than 150,000 pages of the critical information you need to smoothly deploy mission-critical systems and minimize downtime–all while building your technical expertise. To subscribe, see your local authorized retailer, or call (800) 344-2121, Monday through Friday, excluding holidays, 6:30 A.M to 5:30 P.M. Pacific time. • Microsoft Developer Network Library (MSDN): If you develop applications for the Internet or the Windows® operating system, or use Microsoft products for any other development purposes, you'll enhance your productivity with an MSDN subscription. MSDN is Microsoft's official source for technical programming information, SDKs, DDKs, Windows, BackOffice™, Microsoft Office, and Visual Tools for developers. For more information on MSDN subscription levels and benefits, visit MSDN online at: http://www.microsoft.com/msdn/. Or call (800) 759-5474, Monday through Friday, excluding holidays, 6:30 A.M. to 5:30 P.M. Pacific time. • Microsoft Download Service (MSDL): Provides direct modem access to Microsoft’s electronic technical library, which contains sample programs, device drivers, patches, software updates, and programming aids. The service is available 24 hours a day, 365 days a year. In the U.S. dial (425) 936-6735. Connect information: 1200, 2400, 9600, or 14400 baud, no parity, 8 data bits, and 1 stop bit. In Canada, dial (905) 507-3022. Connect information: 1200 to 28800 baud, no parity, 8 data bits, and 1 stop bit. • Microsoft FastTips: An automated toll-free telephone service for quick answers to common technical questions, as well as technical articles by telephone, fax, or mail. To access FastTips or to receive a catalog of the articles available, call one of the following numbers on a touch-tone telephone: Desktop Applications:  (800) 936-4100 Desktop Systems: (800) 936-4200 Development Tools: (800) 936-4300 Business Systems: (800) 936-4400 You can use the following keys on your touch-tone telephone after you reach FastTips.  To do this: Press this key: Advance to the next message * (asterisk) Repeat the current message 7 Return to the beginning of FastTips # Related Topics When You Have a Question Choose the Support Option That’s Right for You Self-Help Tools Online Direct Assistance from a Microsoft Technical Support Engineer Other Microsoft Services Microsoft Technical Support Worldwide


Direct Assistance with a Microsoft Technical Support Engineer
	Direct Assistance with a Microsoft Technical Support Engineer Standard No-Charge Support If you still need answers to your technical questions, Microsoft offers no-charge support for retail* versions of Microsoft Flight Simulator 98 as follows: Unlimited No-Charge Support To receive your Standard No-Charge Support, in the U.S., please call (425) 637-9308, 6 A.M. to 6 P.M. Pacific time, Monday through Friday, excluding holidays. In Canada, please call (905) 568-3503, 5:00 A.M. to 5:00 P.M. Pacific time, Monday through Friday, excluding holidays. Note: Toll-charges may apply. In the U.S. and Canada, you can also submit your support question via the Internet with Web Response. For more details, go to Microsoft Technical Support Online at http://www.microsoft.com/support/. *NOTE If your Microsoft product was pre-installed or distributed with your personal computer or Internet Service Provider (ISP), the personal computer manufacturer or ISP is responsible for providing your product support. For support, contact the manufacturer or source from which you obtained your Microsoft product. When you contact us for support, you should be at your computer and have the appropriate product documentation at hand. Be prepared to give the following information: • The version of the Microsoft product you use. • The type of hardware you use. • The operating system you use. • The exact wording of any messages that appeared on your screen. • A description of what happened and what you were doing when the problem occurred. • A description of how you tried to solve the problem. After-Hours Support If you require support after normal business hours, you can purchase Pay-Per-Incident Support: • In the U.S., for a fee of $15US per incident, please call (800) 936-5600 or (900) 555-2400, 24 hours a day, seven days a week, including holidays.  • In Canada, for a fee of $45CDN plus tax per incident, please call (800) 668-7975, 5:00 A.M. to 9:00 P.M. Pacific time, seven days a week, excluding holidays.  • In the U.S. and Canada, you can also submit your support question via the Internet with Web Response. For more details, go to Microsoft Technical Support Online at http://www.microsoft.com/support/. NOTE Support fees for the (800)# calls will be billed to your VISA, MasterCard, or American Express credit card. Support fees for the (900)# calls will appear on your telephone bill. Priority Annual Support If you anticipate a higher volume of support incidents, or need priority access to Microsoft Technical Support Engineers, you can purchase a Priority Annual Desktop Account as follows:  • In the U.S., for more information or to purchase an annual account at a cost of $295US per 10 incidents, please call (800) 936-3500, 24 hours a day, seven days a week, including holidays. To submit an incident against an existing account, call (800) 936-4700, 24 hours a day, seven days a week, including holidays. • In Canada, for more information, to purchase an annual account at a cost of $295CDN plus tax per 10 incidents, or to submit and incident against an existing account, please call (800) 668-7975, Monday through Friday, excluding holidays, 5:00 A.M. to 9:00 P.M. Pacific time. Related Topics When You Have a Question Choose the Support Option That’s Right for You Self-Help Tools Online Other Self-Help Tools Other Microsoft Services Microsoft Technical Support Worldwide


Other Microsoft Services
	Other Microsoft Services Text telephone Microsoft text telephone (TT/TTY) services are available for the deaf or hard-of-hearing. In the U.S., using a TT/TTY modem, dial (425) 635-4948 between 6:00 A.M. and 6:00 P.M. Pacific time, Monday through Friday, excluding holidays. In Canada, using a TT/TTY modem, dial (905) 568-9641 between 8:00 A.M. and 8:00 P.M. eastern time, Monday through Friday, excluding holidays. Microsoft Customer Service For customer service issues on Microsoft products, upgrades, and services, contact the Microsoft Sales Information Center. In the U.S., call (800) 426-9400. In Canada, call (800) 563-9048. Note: Technical support is not available at these numbers.  Related Topics When You Have a Question Choose the Support Option That’s Right for You Self-Help Tools Online Other Self-Help Tools Direct Assistance from a Microsoft Technical Support Engineer Microsoft Technical Support Worldwide


Microsoft Technical Support Worldwide
	Microsoft Technical Support Worldwide If you are outside the U.S. and have a question about a Microsoft product, first: • Check the information in this Help file or product manual. • Check the readme files that come with your product disks. These files provide general information that became available shortly before the product was released. • Go to Microsoft Technical Support Online at http://www.microsoft.com/support/. If you cannot find a solution, you can receive information on how to obtain product support by contacting the Microsoft subsidiary office in your area. Calling a Microsoft Subsidiary Office When you call your local Microsoft subsidiary, you should be at your computer and have the appropriate product documentation at hand. Be prepared to provide the following information: • The version of the Microsoft product you use. • The type of hardware you use, including network hardware, if applicable. • The operating system you use. • The exact wording of any messages that appeared on your screen. • A description of what happened and what you were doing when the problem occurred. • A description of how you tried to solve the problem. • Microsoft subsidiary offices and the countries they serve are listed below. If there is no Microsoft subsidiary office in your country, please contact the establishment from which you obtained your Microsoft product. Microsoft Worldwide Subsidiaries • Argentina Microsoft de Argentina S.A.  Customer Service: (54) (1) 819-1900 Fax: (54) (1) 819-1921 Technical Support: (Consumer, POS, and DAD): (54) (1) 314-0560 (BSD and DD, only for installation): (54) (1) 819-1900 • Australia Microsoft Pty. Ltd. Fax: (61) 02 9805 0519 Sales Information Centre: (61) 02 9870 2100 Installation Support: (61) 02 9870 2132 Bulletin Board Service: (61) 02 9878 5200 Technical Support: (61) 02 9870 2131 • Austria Microsoft Ges.m.b.H. Phone: 0222-68 76 07 Fax: 0222-68 16 2710 Information: 0660-6520 Prices, updates, etc.: 0660-6520 CompuServe: GO MSEURO (Microsoft Central Europe) Standard Support: Installation and Handling Windows 95: 0660-6510 Microsoft Excel for Windows: 0660-6511 Microsoft Access: 0660-6761 TechNet, Developer Network, Bookshelf: 0660-6506 General information about Support Network in Central Europe: FAX: 0049/2622/167006 • Belgium Microsoft NV Phone: +32-2-730 39 11 Fax: +32-2-726 96 09 Microsoft Information Center: +32-2-481 52 52 CompuServe: 02-2150530 (GO MSBEN) Bulletin Board: +32-2-726 85 45 (14400/1200/2400/9600 bd, 8N1, ANSI) Technical Support: +32-2-513 32 74 (Dutch speaking) +32-2-502 34 32 (English speaking) +32-2-513 22 68 (French speaking) • Bolivia See Argentina • Brazil Microsoft Informatica Ltda. Phone: (55) (11) 514 –7100 Fax: (55) (11) 514 - 7106/514-7107 Technical Support: Phone: (55) (11) 871-0090 Fax: (55) (11) 262-8638 Technical Support Bulletin Board Service: (55) (11) 872-4106 Technical Support Help by Fax: (55) (11) 871-4701 • Canada Microsoft Canada Inc. Head Office Phone: 1 (905) 568-0434 Customer Support Centre: 1 (800) 563-9048 Technical Support: Desktop Systems including Microsoft Windows 95: 1 (905) 568-4494 Microsoft Office and Office Components: 1 (905) 568-2294 Other Standard Technical Support: 1 (905) 568-3503 Priority Support Information: 1 (800) 668-7975 Text Telephone (TT/TDD) 1 (905) 568-9641 Technical Support Bulletin Board Service: 1 (905) 507-3022 • Caribbean Microsoft Caribbean, Inc. Phone: (809) 273-3600 Fax: (809) 273-3636 Technical Support: (214) 714-9100 • Central America See Latin America • Chile Microsoft Chile S.A. Phone: 56-2-330-6000 Fax: 56-2-330-6190 Customer Service: 56-2-800-213121 Personal Operating System and Applications: Phone: 56-2-330-6222 Fax: 56-2-341-1439 • Colombia Microsoft Colombia Phone: (571) 618 2245 Fax: (571) 618 2269 Technical Support: (571) 618 2255 • Czech Republic Microsoft s.r.o. Phone (+420) (2) 611 97 111 Fax: (+420) (2) 611 97 100 Technical Support:  (+420) (2) 2150 3222 or 53 52 56 (Windows 95 only) • Denmark Microsoft Denmark AS Phone: (45) (44) 890 100 Fax: (45) (44) 685 510 Technical Support: Phone: (45) (44) 89 01 11 Microsoft Sales Support: (45) (44) 89 01 90 Microsoft FaxSvar: (45) (44) 89 01 44 Microsoft BBS: (45) (44) 66 90 46 (Document 303030 in FaxSvar contains detailed instructions) Microsoft MSDL: (45) (44) 66 90 46 Microsoft FastTips: (45) (44) 89 01 44 • Dubai Microsoft Middle East Phone: (971) 4 513 888 Fax: (971) 4 527 444 • Ecuador Corporation Microsoft del Ecuador S.A. Phone: (593) 2 460-447, (593) (2) 460-451 Customer Service: (593) (2) 460-453, (593) (2) 460-458 Technical Support: (593) (2) 463-094 • Egypt Microsoft Egypt Phone: +202-418-5571 Fax: +202-4174766 • England See United Kingdom • Finland Microsoft OY Phone: (358) (90) 525 501 Fax: (358) (90) 522 955 Product Support: Phone: (358) (90) 525 502 500 Microsoft FaxSvar: (46) (0) 8-752 29 00 (Information in Swedish and English) Microsoft BBS: (46) (0) 8-750 47 42 (Information in Swedish and English) Microsoft MSDL: (358) (90) 455 03 66 Microsoft FastTips: (358) (90) 525 502 550 For Technical Support, please contact your local reseller. • France Microsoft France Phone: (33) (1) 69-86-46-46 Fax: (33) (1) 64-46-06-60 Telex: MSPARIS 604322 Technical Support Phone: (33) (1) 59-85-96-33 (Province)/33 3 49 49 49 57(2) Technical Support Fax: (33) (1) 69-28-00-28 Fax Information Service: (33) (1) 36-70-13-13 • French Polynesia See France • Germany Microsoft GmbH Phone: 089/3176-0 Fax: 089/3176-1000 Telex: (17) 89/83 28 MS GMBH D Information: 089/3176 1199 Prices, updates, etc.: 089/3176 1199 CompuServe: GO MSEURO (Microsoft Central Europe) Bulletin board, device drivers, tech notes:  Btx: *microsoft# or *610808000#  Standard Support: Installation and Handling Windows 95: 089/3176-1115 Microsoft Excel for Windows: 089/3176-1120 Microsoft Access: 089/3176-1180 TechNet, Developer Network: 089/3176-1810General information about Microsoft support in Central Europe: Fax: 02622/167006 • Greece Microsoft Hellas, S.A. Phone: (30)(1) 6806-775 through (30)(1) 6806-779 Fax: (30)(1) 6806-780 • Hong Kong Microsoft Hong Kong Limited Fax: (852)2560-2217 Product support Faxback Service: (852)2535-9293 Microsoft Club Upgrade Centre:  (852)2880-5085 Microsoft Club Member Hotline:  (852)2516-5113 Technical Support: (852) 2804-4222 • Hungary Microsoft Hungary Phone: +36 (1) 268-1668 Fax: +36 (1) 268-1558 Technical Support: +36 (1) 267-4636 (2MSINFO) • Iceland See Denmark • Ireland See United Kingdom • India Microsoft India Phone: (011) (91) (11) 646 0694, 646 0767, 646 0813 Fax: (011) (91) (11) 646-0813 • Indonesia (SP) Microsoft Indonesia - Jakarta Technical Support Phone: 62 21 5721060 Fax: 62 21 5732077 • Israel Microsoft Israel Ltd. Phone: 972-3-613-0833 Fax: 972-3-613-0834 • Italy Microsoft SpA Phone: (39) (2) 7039-21 Fax: (39) (2) 7039-2020 Microsoft by Fax (Fax-on-demand service):  (39) (2) 70-300-703 Customer Service (New product info, product literature):  (39) (2) 70-398-398 Dealer Support (Customer Service for resellers only):  (39) (2) 70-398-388 Bulletin Board: (39) (2) 7030-0102 Technical Support: (39) (2) 70-398-351 Microsoft Consulting Service: (39) (2) 7039-2400 Microsoft Rome Office: (39) (6) 5432-497 • Japan Microsoft Company Ltd. Technical Support: (81) (424) 41-8700 Fax Information Service:  (81) (3) 5454-8100 (1#-0# for guidance) Microsoft Support Sales:  (Technical Support options/ Support Contract) Phone: 0120-37-0196 (toll free domestic only) Channel Marketing Information Center:  (Presales Product Support) Phone: (81) (3) 5454-2300 Fax: (81) (3) 5454-7951 Customer Service Phone : (Version upgrade/Registration) Phone: (81) (3) 5454-2305 Fax: (81) (3) 5454-7952 • Korea Microsoft CH Phone: (82) (2) 531-4500 Fax: (82) (2) 531-1724  Office Technical Support: (82) (2) 508-0040 Windows Technical Support: (82) (2) 563-0054 Developer Technical Support: (82) (2) 566-0071 Technical Support Fax: (82) (2) 531-4600 Technical Support Bulletin Board Service:  (82) (2) 538-3256 • Latin America Microsoft Latin American Headquarters (U.S.A.) Phone: (305) 489-4800 Fax: (305) 491-1616 Customer Service: (425) 936-8661 Technical Support: (214) 714-9100 • Liechtenstein See Switzerland (German speaking) • Luxembourg Microsoft NV Phone: +32-2-730 39 11 Microsoft Information Center: +32-2-481 52 52 CompuServe: +32-2-215 05 30 (GO MSBEN) Bulletin Board: +32-2-726 85 45  (1200/2400/9600/14400 bd, 8N1, ANSI) Technical Support: +32-2-513 32 74 (Dutch speaking) +32-2-502 34 32 (English speaking) +32-2-513 22 68 (French speaking) • Malaysia (SP) Microsoft (Malaysia) Sdn Bhd: Phone: (60-3) 793-9595 Fax: (60-3) 791-6080 • México Microsoft México, S.A. de C.V. Technical Support: (Applications and Operating Systems) (52)(5) 325-0912 Customer Service. (52)(5) 325-0911 Fast Tips: (52)(5) 237-4894  (24 hours x 365 days service) Bulletin Board Service: (52)(5) 628-6200  (2400s/14400k baud, 8 bits, No parity, 1 stop bit, ANSI terminal emulation) (52)(5) 628-6202 (14400k baud, 8 bits, No parity, 1 stop bit, ANSI terminal emulation) User: MSMEXICO, NO Password • Morocco Microsoft Afrique Du Nord Phone: (212) 2 47 10 72 Fax: (212) 2 47 10 86 • Netherlands Microsoft BV Phone: 023-5689189 Customer Service: 023-5677700 CompuServe: 020-6880085 (GO MSBEN) Bulletin Board: 023-5634221  (1200/2400/9600/14400bd, 8N1, ANSI) Technical Support: 023-5677877 (Dutch speaking) 023-5677853 (English speaking) • New Zealand Microsoft New Zealand Ltd Phone: 64 (9) 358-3724 Fax: 64 (9) 358-3726 Technical Support: Phone: 64 (9) 357-5575 Fax: 64 (9) 307-0516 and 357-5577 • Northern Ireland See United Kingdom • Norway Microsoft Norway AS Phone: (47) (22) 02 25 00 Fax: (47) (22) 95 06 64 Product Support: (47) (22) 02 25 50 Microsoft Sales Support: (47) (22) 02 25 80 Microsoft BBS: (47) (22) 18 22 09 (Document 404040 in FaxSvar contains detailed instructions) Microsoft FaxSvar: (47) (22) 02 25 70 Microsoft MSDL: (47) (22) 18 22 09 Microsoft FastTips: (47) (22) 02 25 70 • Papua New Guinea See Australia • Paraguay See Argentina • Peru See Latin America • Philippines (SP) Microsoft Philippines  Phone: 632 811 0062 Technical Support: Phone : 632 892 2295/2495 Fax: 632 813 2493 • Poland Microsoft Sp. z o.o. Phone: (+48) (22) 661-5433 Fax: (+48) (22) 6615434 Information Service: (+48) (22) 6286924 Technical Support:  (+48) (22) 6216793 or (+48) (71) 441357 • Portugal Microsoft Portugal MSFT, Lda. Phone: (351) 1 4409200 Fax: (351) 1 4412101 Technical Support: Standard Support (All Clusters):  (351) 1 4409280/1/2/3 Fax : 351 1 4411655 • Republic of China Microsoft Taiwan Corp. Phone: (886) (2) 504-3122 Fax: (886) (2) 504-3121 Technical Support: (886) (2) 508-9501 • Republic of Ireland See United Kingdom • Russia Microsoft A/O Fax: (+7) (502) 224 50 45 • Scotland See United Kingdom • Saudi Arabia Microsoft Saudi Arabia Phone: +966-1-488-1165 Fax: +966-1-488-1576 ext 300 Technical Support (POS and DAD only): Phone: 800 124 0500  (toll free within Saudi Arabia) Fax: 966-1-4740576 • Singapore Microsoft Singapore Pte Ltd Phone: (65) 337-6088 Fax: (65) 337-6788 Customer Services: Phone: (65) 433-5488 Fax: (65) 339-9958 Product Support Services: Phone: (65) 337-9946 Fax: (65) 337-6700 • Slovenia/Slovenija Microsoft d.o.o. (see Germany also) Phone: +386 61 1881 133 Fax: +386 61 1881 137 Technical Support:  +386 61 123 23 54 or +386 64 331 020 • Slovak Republic Microsoft Slovakia s.r.o. 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accelerated stall

A stall induced by turns, pull-ups or other maneuvers that increase the load factor (G-load) on an airplane. The loads imposed by such maneuvers typically increase the speed at which a wing stalls, but they do not affect the angle of attack at which the stall occurs. That angle, the critical angle of attack, is always the same.


ace

A military pilot who has destroyed at least five enemy aircraft. The term originated in France during World War I, where it was given only to top pilots who had downed at least 10 aircraft. Later "ace" was commonly used for any pilot who claimed at least five aircraft. German aces in WWI were called Kanone ("cannons").


active runway

The runway currently in use for takeoffs and landings. Many large airports have more than one runway, usually arranged in a pattern to take advantage of prevailing winds. Some airports have parallel runways to accommodate more takeoffs and landings. Under specific conditions at airports with operating air traffic control towers, aircraft may also use intersecting runways for takeoffs and landings to expedite the traffic flow.


advection

The horizontal movement of air or atmospheric properties. In meteorology, this process is sometimes referred to as the horizontal component of convection.


advection fog

Fog resulting from the movement of warm, humid air over cooler ground or water. Advection fog is most common along coastal areas, although it often develops deep in continental areas. At sea it is called "sea fog." Advection fog deepens as wind speed increases up to about 15 knots. Stronger winds lift the fog into a layer of low stratus or stratocumulus.


advisory circulars (ACs)

In the U.S., non-regulatory information and procedures published by the FAA. Advisory circulars provide background information and more detail on subjects not completely outlined in the FARs or AIM. Advisory circulars are published by the Government Printing Office; many publishers also reprint important ACs as references for pilots. ACs are arranged in series, designated by a two- or three-digit number. Those in series 00 cover general subjects. ACs in the 10 series deal with procedural rules. ACs in the 20 series deal with aircraft; those in the 60 series cover pilots. ACs in the 70s series deal with airspace, while 90-series ACs cover air traffic and general operating rules. Issues related to air carriers (airlines) are covered in 120-series ACs.


aerobatics

Precision maneuvers such as barrel rolls, loops, hammerhead stalls, spins, and Cuban eights. Often performed at airshows and competitions, many of these maneuvers are also part of a military pilot's training and can be used in aerial combat. In fact, many basic aerobatic maneuvers evolved from air combat tactics invented during World War I.

"Aerobatics" is also defined in FAR 91.303, which describes restrictions on aerobatic flight. In that section, "aerobatic flight" means "any intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight."


aerodynamics

The study of air in motion, in particular, the interactions between air and surfaces such as an aircraft wing. Aerodynamicists are scientists and engineers who specialize in aerodynamics. They use wind tunnels, computer models, and other tools to design and build aircraft and airfoils.


aeronaut

The pilot or navigator of an airship or balloon. Famous aeronauts include the Montgolfier brothers, inventors of the hot-air balloon; Henri Giffard, builder and pilot of the first powered dirigible; and August Piccard, who rode a balloon into the stratosphere.


aeronautics

The study or science of flight.


Aérospatiale

State-controlled French aircraft manufacturing company formed by the merger of Sud Aviation and Nord Aviation. Based in Toulouse, Aérospatiale has produced a wide range of helicopters and is the manufacturer of the supersonic Concorde airliner.


aerostats
aerostat

A lighter-than-air craft, such as a hot-air balloon or dirigible, that gets lift principally from buoyancy instead of generating lift with airfoils.


afterburner

Device that injects fuel into the exhaust stream of a turbojet engine. The combustion of the unburned oxygen from the exhaust and the jet fuel provides an extra boost at takeoff or during combat maneuvers. Also known as "reheat," especially in Great Britain.


AGL

Abbreviation for "above ground level." The heights of clouds in airport weather observations and forecasts is usually reported in AGL.


ailerons

Movable control surfaces, usually located near the wing tips, that control the rolling motion of an aircraft. The pilot deflects the ailerons by moving the control yoke or stick left and right. The ailerons move simultaneously in opposite directions. For example, when the pilot moves the yoke or stick left, the aileron on the left wing moves up, decreasing the lift on the left wing. At the same time, the right aileron moves down, increasing the lift on the right wing. The word derives from the French word aile, "wing."


AIM

Abbreviation for "Aeronautical Information Manual," an official source of information about navigational aids, airport operations, air traffic control procedures, and other subjects of importance to pilots and air traffic controllers. Published by the FAA, the AIM is available from many publishers in printed and electronic formats.


airfoil

A device that interacts with a moving stream of air to produce lift or thrust. Wings, propellers, tail surfaces, helicopter rotor blades, ailerons and other control surfaces, and turbine blades are all airfoils.


airline transport pilot certificate (ATP)

In the U.S., the pilot certificate required to act as pilot in command of an aircraft for an air carrier (airline) and for certain other operations. The ATP is the "Ph.D." of aviation. To be eligible for an ATP certificate, a pilot must be at least 23 years old and hold a current first class medical certificate. In general, an ATP applicant must also have at least 1500 hours of flight time, including minimum amounts of time on cross-country flights, flights at night, and instrument flight time.


air mass

In meteorology, an extensive body of air within which the conditions of temperature and moisture in a horizontal plane are essentially uniform.


air taxi

The preferred method for helicopter movement to and from the takeoff and landing area. Unless otherwise requested or instructed, during air taxi, pilots are expected to remain below 100 ft (30 m) above ground level. The use of the air taxi procedure enables the helicopter to proceed at the optimum airspeed and altitude, minimize rotor downwash, conserve fuel, and expedite movement between areas. The pilot is solely responsible for selecting a safe airspeed and for ensuring that the helicopter’s downwash does not injure people or damage property.


Air Traffic Control
air traffic control (ATC)

A network of control towers, approach and departure controls, and en route control centers designed to ensure the safe and efficient flow of air traffic. ATC's primary responsibility is to maintain separation between aircraft operating under Instrument Flight Rules (IFR), but ATC also provides services to aircraft operating under Visual Flight Rules (VFR).

ATC's functions are divided into several segments. Ground control supervises aircraft taxiing to and from runways. The tower or "local control" handles aircraft in the vicinity of an airport, clearing them for takeoff or landing. Departure and approach controls manage the airspace surrounding one or more airports, and en route centers control traffic between airports.


Airbus Industrie

Aircraft manufacturing consortium that includes France's Aérospatiale, Germany's Deutsche Airbus, British Aerospace, and CASA of Spain. Based in Toulouse, France, Airbus is the world's second-largest manufacturer of commercial airplanes (after Boeing). Its major products are the A310, A320, A321, A330, and A340 airliners.


aircraft

A flying machine. In the U.S., the FAA divides aircraft into classes and categories. With respect to the certification of aircraft, classes are broad groupings such as airplanes, rotorcraft, gliders, balloons, landplanes, and seaplanes. Categories define aircraft based on their intended use or operating limitations; for example, transport, normal, utility, acrobatic, limited, experimental, restricted, and provisional. With respect to the certification of pilots, class means a classification of aircraft with similar operating characteristics; for example, single engine, multiengine, land, water, and helicopter. Category means a broad classification of aircraft, such as airplane, rotorcraft, and glider.


airship

An engine-driven, lighter-than-air aircraft that can be steered.


airspace

The part of the atmosphere that lies above the surface and is under the jurisdiction of a nation or controlling authority. In the U.S., there are two categories of airspace—regulatory and nonregulatory. Within those two categories, there are four types of airspace—controlled, uncontrolled, special use, and other. Airspace is assigned to one of the types according to the density and complexity of the air traffic using the airspace, the types of operations conducted in that airspace, and other factors.


airspeed

The rate at which an aircraft moves through the surrounding air. Pilots use several types of airspeed during flight. For example, indicated airspeed (IAS) is the speed shown on the airspeed indicator (usually in knots). Pilots use IAS to control an aircraft and manage its performance. Calibrated airspeed (CAS) is IAS corrected for instrument and installation error. True airspeed (TAS) is IAS corrected for changes in atmospheric temperature and pressure. Pilots use TAS to solve navigation problems.

The aircraft's speed over the ground—ground speed—is TAS corrected for the effect of a headwind or tailwind.


airspeed indicator

The instrument that displays an aircraft's speed relative to the air in which it is moving. Most modern aircraft have airspeed indicators calibrated in knots or in Mach number.


Al Mooney

1906–1986. American airplane designer and manufacturer. Mooney began designing light airplanes in 1922. He worked for a number of aircraft companies around the U.S., including Bellanca and Culver Aircraft, before joining Dart Manufacturing to design the Dart monoplane. Mooney designed his M-18 Mite in 1946; that same year he and his brother Art founded Mooney Aircraft.


Alberto Santos-Dumont

1873–1932. Brazilian-born inventor of dirigibles and airplanes who made the first powered flight in Europe. Santos-Dumont made his first balloon flight early in 1898; later that year he became the first to fly a balloon equipped with an engine. In 1906 he flew his boxlike "14-bis" flying machine 722 ft (220 m) for the first powered flight outside the U.S. Santos-Dumont retired from aviation in 1910. In 1932, depressed over the military use of aircraft, he took his own life.


Alexander Graham Bell

1847–1922. Scottish-born American inventor. Bell's early experience in teaching the deaf led to an interest in communications. By 1875 he was an expert in electric wave transmission, and the following year he invented the telephone. In 1892 Bell became interested in aviation. He experimented with kites, photographed Samuel Langley's successful launch of the model Aerodrome, and later formed the Aerial Experiment Association with a group of young aviators that included Glenn Curtiss.


altimeter setting

The value to which the scale of a pressure altimeter is set so it reads true altitude at field elevation. The setting is usually given in inches of mercury (Hg) or millibars.


altocumulus

White or gray layers or patches of middle clouds, often with a waved appearance. Altocumulus clouds appear as rounded masses or rolls. They are composed mostly of liquid water droplets which may be supercooled. At subfreezing temperatures, altocumulus clouds may contain ice crystals.


altocumulus castellanus

A type of middle cloud that includes some vertically developed, cumuliform protuberances (some of which are taller than they are wide, as castles). These cumuliform sections give the cloud a crenellated or turreted appearance; especially evident when seen from the side. This cloud indicates instability and turbulence at the altitudes where it appears.


altostratus

Stratiform—flat, layered—clouds that form in the middle altitudes. The height of their bases ranges from 6,500–23,000 ft (1,980–7,000 m) in middle latitudes.


Amelia Earhart

1897–1937. American aviator, the first woman to fly solo nonstop across the Atlantic. Earhart was also the first woman to cross the U.S. nonstop (1932) and the first pilot to fly solo from Hawaii to California (1935). As an aeronautics adviser at Purdue University and an active proponent of women's aviation, she decided to attempt the first around-the-world flight made by a woman. Her second try in 1937 ended when she and navigator Fred Noonan disappeared over the Pacific.


anemometer

An instrument for measuring wind speed.


aneroid barometer

A barometer that operates on the principle of changing atmospheric pressure bending a metallic surface which, in turn, moves a pointer across a scale graduated in units of pressure.


angle of attack
angle of attack (AOA)

The angle between a wing or rotor and the oncoming airflow—the relative wind. It's important to understand that the angle of attack is related to the direction in which an aircraft is moving, not to the angle the wing or rotor makes with the horizon. In general, as angle of attack increases, so does the amount of lift a wing or rotor produces. However, at a specific point called the "critical angle of attack," the air flowing over a wing or rotor can no longer follow the airfoil's contour, and it becomes turbulent. The sudden loss of lift at this point is called a "stall."


angle of incidence

The angle at which a wing or propeller blade is mounted to the aircraft fuselage or to the propeller hub. The pilot cannot control the angle of incidence.


anticyclone

An area of high atmospheric pressure with a closed anticyclonic circulation. Viewed from above, the circulation is clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere, and undefined at the equator.


anti-torque pedals

In a helicopter, the flight controls that adjust the thrust produced by the tail rotor. Pilots use the anti-torque pedals to counteract the effects of torque caused by rotation of the main rotor and to trim the helicopter in flight. In a hover, the pilot uses the anti-torque pedals to turn the helicopter and to maintain heading—the direction in which the nose is pointed.

If you add power by increasing collective, you must add left pedal pressure to counteract the increased torque from the main rotor. If you reduce power by lowering the collective, apply right pedal pressure to compensate for decreased main rotor torque.

In a hover, applying left pedal turns the helicopter left; pressing right pedal turns the helicopter to the right.


anvil cloud

Popular name given to the top portion of a cumulonimbus (thunderstorm) cloud that has an anvil-like appearance.


approach lighting system
approach lighting system (ALS)

Color-coded or sequenced flashing lights that clearly define the approaches to a runway. The ALS helps pilots make the transition to visual references at the end of an instrument approach. It can also aid pilots operating at night under visual flight rules (VFR).


area forecast (FA)

In the U.S., a forecast of general weather conditions over an area the size of several states. It is used to forecast en route weather and to interpolate conditions at airports that do not issue terminal forecasts. FAs are issued three times a day by the National Aviation Weather Advisory Unit (NAWAU) in Kansas City, Mo., for each of six areas in the contiguous 48 states. Other offices issue reports for Alaska, Hawaii, and the Gulf of Mexico.

An area forecast contains a 12-hour specific forecast, followed by a 6-hour (18-hour in Alaska) categorical outlook, giving a total forecast period of 18 hours. The information in an FA includes several parts, including a synopsis, VFR clouds and weather, and other items of significance to VFR flight, including thunderstorms and strong winds, if forecast.


area rule

An aeronautical engineering principle that helps designers reduce drag at speeds near the speed of sound. Pinching in the fuselage where it meets the canopy, tail, or wings—creating the so-called Coke-bottle effect—cuts drag dramatically, reducing the amount of power an aircraft needs to reach supersonic speeds.


Aresti notation

A system of "aerocryptographics" for pilots and judges at aerobatic competitions and airshows. Named for Prince Aresti, an aerobatic pilot who devised the notation system and built a dictionary of maneuvers and sequences.


aspect ratio

The ratio between the length (span) and width (chord) of a wing. In general, a wing with a high aspect ratio is more efficient than a wing with a smaller aspect ratio.


attitude indicator
attitude indicator (artificial horizon)

The instrument that shows the aircraft's pitch and bank attitudes with respect to the ground. Pilots use the attitude indicator, sometimes called the "artificial horizon," when the true horizon isn't visible.


auto coordination
auto-coordination

In Flight Simulator, an option that automatically synchronizes the actions of the ailerons and rudder to maintain coordinated—balanced—flight, especially during turns. You can turn auto-coordination on or off by clicking the Aircraft Settings command on the Aircraft menu.


autogyro

An engine-powered aircraft that uses a propeller for forward motion and a large, free-rotating, horizontal rotor for lift. Also spelled "autogiro."


automatic direction finder
automatic direction finder (ADF)

A radio navigation instrument that receives signals from nondirectional radio beacons (NDBs) or AM radio stations. The needle on the ADF indicator always points toward the selected radio signal. A pilot can determine the magnetic bearing to the station by using the formula Relative Bearing + Magnetic Heading = Magnetic Bearing.


automatic pilot
automatic pilot (autopilot)

A device that automatically controls an aircraft. Similar in concept to the cruise control feature on an automobile, simple autopilots keep an airplane's wings level. More sophisticated autopilots can fly an airplane from immediately after takeoff all the way to its destination and then make an automatic landing. Autopilots use gyros and other sensors to keep track of the airplane's altitude, speed, and position, and then send signals to the appropriate controls to keep the airplane on course and at a specific altitude.


automatic terminal information service
Automatic Terminal Information Service (ATIS)

A continuous-loop recording played over a specified frequency that gives pilots the current weather, runway or runways in use, and other information. ATIS is available at many airports with an operating control tower. The tape is updated hourly or whenever there is a significant change in weather or airport information. Each update is labeled with a letter of the alphabet, which is pronounced according to the ICAO standard. For example, the broadcast at 11:00 might be designated "Information Delta"; the next update would be designated "Information Echo." Pilots are expected to listen to the ATIS and indicate that they have received the current information before they make initial contact with air traffic controllers.


autorotation

In a helicopter, a descent during a simulated or actual engine failure. During an autorotation, the engine is disengaged from the main rotor. The main rotor turns because air flows up through the rotor disk as the helicopter descends. That is, the rotor windmills. The pilot must lower the collective to preserve main rotor RPM during the descent and then raise the collective near the ground to cushion the landing.


avionics

Derived from "aviation electronics," this term most commonly refers to the electronic communication, navigation, and flight-control equipment on board an aircraft.


axial-flow

Flow of air in a path parallel to the center. In an axial-flow turbine engine, air enters the front and follows a straight path through a series of turbine blades that compress the air before it enters the combustion chamber.


axis indicator

In Flight Simulator, a display that shows the current axis of the aircraft and gives a good indication of where the aircraft's center is pointing. You can turn the axis indicator on and off or change its shape by choosing View Options from the Views menu, and then choosing an Axis Indicator option.


balloon (verb)

To increase the pitch attitude and angle of attack too rapidly. Ballooning can lead to a low-altitude stall, a hard landing, or porpoising if a tricycle-gear airplane lands nose-wheel first.


bank

The angle of an airplane's wings with respect to horizon; rotation about an aircraft's longitudinal axis. Pilots control bank with the ailerons. Airplanes turn principally because banking the wings creates a horizontal component of lift. Pilots measure bank in degrees.


barnstormer

A pilot who tours the countryside, performing at exhibitions and taking passengers on sightseeing flights.


barometer

An instrument for measuring the pressure of the atmosphere. The two most common types are mercurial and aneroid.


barometric altimeter

A barometer that measures altitude by registering changes in atmospheric pressure as an aircraft climbs or descends. Large aircraft often are also equipped with a radio altimeter that measures the height of an aircraft by sending a radio beam to the ground and converting the time it takes to return into height above the surface. Radio altimeters are particularly useful during instrument approaches.


Bernoulli's principle

The physical law stating that the total energy of fluid in motion remains constant: If its speed increases, its pressure drops; if its speed decreases, its pressure increases. Wings are designed to exploit this relationship by accelerating air that passes over their curved upper surfaces, thereby decreasing its pressure. The difference between the lower pressure above a moving airfoil and the relatively higher pressure below, creates lift. This principle was first established by the Swiss scientist Daniel Bernoulli (1700–1782). Although aeronautical engineers continue to debate the theory of how lift is created, Bernoulli's principle is still regarded as a fundamental explanation of how airfoils produce lift.


Bill Piper

1881–1970. American aircraft manufacturer who founded Piper Aircraft Corporation in 1937. Piper left his earlier career in oil exploration to invest in Taylor Brothers, builder of the E-2 Cub. He took over the company in 1932 and changed its name five years later. Piper Aircraft was for many years the world's leading producer of light aircraft.


bleed off

To decrease airspeed or altitude in a slow, carefully controlled manner.


blimp

A nonrigid airship generally shaped like a cigar. Internal gas pressure maintains both the blimp's buoyancy and its shape. There are many theories as to the term's origin—one of the most popular states that "blimp" is the sound made if you plunk the envelope with your finger.


Boeing

American aircraft company, founded by William Boeing in 1916, and today the world's largest manufacturer of commercial airplanes. Boeing also produces military aircraft and spacecraft, but it is best known for its "7" series of passenger jetliners—the 707, 727, 737, 747, 757, 767, and 777.


buffet

Vibration, usually affecting the horizontal stabilizer and elevator, caused by turbulent airflow. Buffet occurs as the wing approaches its critical angle of attack and the smooth flow of air over the top surface of the wing becomes turbulent, like water flowing over rocks. This turbulent air strikes the airplane's tail surfaces and induces a mild vibration that the pilot feels through the flight controls. Pilots use the onset of buffeting as one indication of an impending stall.


Buys Ballot's law

The law that states that if an observer in the Northern Hemisphere stands with his or her back to the wind, lower pressure is to the left.


calibrated airspeed (CAS)

Indicated airspeed (IAS) corrected for instrument and installation error. The position of the pitot tube and static ports, flap setting, and pitch attitude of an aircraft can affect the accuracy of the airspeed indicator—especially at the low end of an airplane's speed range. Aircraft operating handbooks and placards on the instrument panel often include a table to help pilots determine CAS.


canard

A horizontal surface, mounted ahead of an aircraft's main wing, that serves as a stabilizer to control pitch. Canards also reduce drag by cutting the down force generated by a conventional tail. Canards were first used in the pioneering days of aviation, and today their principle advantage in modern design is in preventing deep stalls. The canard is designed to stall before the main wing, lowering the angle of attack of the main wing before that wing can stall. The term "canard" is also used to describe any aircraft that flies tail-first.


canted gyroscope

A gyroscope within a flight instrument, usually the turn coordinator, with its rotational axis tilted or canted with respect to the aircraft's longitudinal axis. The tilted axis causes the gyro to respond to a banking or yawing motion.


cantilever wing

A wing attached to the fuselage without external struts or wire bracing.


carburetor

The part of a piston engine that mixes fuel and air, creating a combustible mixture that is ignited and burned in the cylinders. Filtered air enters the carburetor through a venturi, a narrow throat. As the air flows through the venturi, its velocity increases. The air pressure drops, creating a partial vacuum that draws in fuel through a needle valve. The fuel, atomized into tiny drops, mixes with the air, and the mixture flows into the intake manifold, a tube with branches that delivers the mixture to each cylinder.


certified flight instructor certificate

In the U.S., a certificate that allows a person to give instruction to applicants for other pilot certificates. To be eligible for a certified flight instructor (CFI) certificate, a person must be at least 18 years old and hold a current second class medical certificate and a commercial pilot certificate. The applicant must demonstrate proficiency in teaching and in demonstrating the maneuvers required for various pilot certificates. A CFI certificate must be renewed every 24 months.


category (aircraft)

In the U.S., with respect to the certification of aircraft, a grouping based on intended use or operating limitations. In the U.S., all aircraft are certified in a specific category. Examples include: transport, normal, utility, acrobatic, limited, restricted, and provisional. With respect to pilot certification, category means a broad classification of aircraft, such as airplane, rotorcraft, and glider.


ceiling

The height above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as "broken" or "overcast." The height of the ceiling is one of the factors that determines whether flight under visual flight rules (VFR) is possible. In the United States, the ceiling generally must be at least 1,000 ft (305 m) for operations under VFR in controlled airspace.


ceilometer

A cloud height measuring system. It projects light on the cloud, detects the reflection by a photoelectric cell, and determines height by triangulation.


cell

Another name for a thunderstorm or cumulonimbus cloud. Pilots, air traffic controllers, and meteorologists often use this term to report areas of intense precipitation, lightning, or turbulence associated with a thunderstorm.


center of gravity (CG)

The point at which an airplane would balance if it were suspended by a cable. The CG is also the point at which the three axes—longitudinal, lateral, and vertical—of an airplane intersect and the point at which the four fundamental forces of flight—lift, weight, thrust, and drag—are assumed to act.

Pilots must ensure that the CG of a loaded aircraft falls within a specified range, called the "CG envelope." If the CG is outside the envelope, the aircraft may be difficult or impossible to control. To determine the position of the CG, divide total aircraft moment by total weight.


centrifugal flow

Flow of air outward from the center of rotation. Early turbine engines used the principle of centrifugal flow to compress air before it entered the combustion chamber.


Cessna Aircraft Company

American manufacturer of aircraft, founded in 1927 by Clyde Cessna. Production of the Cessna "A" series began in 1928, but the Great Depression brought business to a near standstill. However, the success of civil and military versions of the T-50 "Bamboo Bomber" created a wartime boom for Cessna that helped the company later produce more aircraft than any other manufacturer.


Charles A. Lindbergh

1902–1974. American aviator who was the first pilot to make a solo, nonstop flight across the Atlantic, for which he won the Orteig Prize and the Medal of Honor. Lindbergh started his career as a barnstormer and airmail pilot. After his historic flight, he and his wife Anne mapped air routes for Pan Am. Lindbergh eventually moved to Hawaii, where he wrote several books, including "The Spirit of St. Louis," which won a Pulitzer Prize in 1954.


chord

Also called the "chord line," an imaginary line drawn in cross-section from the leading edge to the trailing edge of a wing. The chord line is the reference used to determine the angle of attack and to draw lift, weight, and other vectors when analyzing a wing that is producing lift.


Capt. Chuck Yeager
Chuck Yeager

1923– . American Air Force officer and fighter pilot, test pilot, and the first person to fly faster than the speed of sound (1947). Yeager, who achieved the rank of brigadier general in 1968, received numerous decorations, including the Distinguished Service Medal, the Purple Heart, and the Presidential Medal of Freedom. Yeager made his most famous flight despite two broken ribs he sustained in a riding accident just days before the flight.


CIGAR check
CIGARS check

A memory aid to help pilots check critical items before takeoff. The letters of this acronym usually stand for:

C: Controls; check flight control freedom and correct movement.

I: Instruments; check flight and engine instruments for proper settings and indications.

G: Gas; check fuel quantity, and that the fuel tank selector is set to fullest tank or “Both.”

A: Altimeter; check altimeter setting and indication.

R: Runup; check engine performance at the recommended power setting.

S: Seatbelts; check that seat belts and shoulder harnesses are fastened and adjusted.

There are many variations of this basic memory aid. Some pilots add letters or substitute other items for the letters in this acronym.

The GUMPS check is a similar mnemonic to help pilots remember to check critical items before landing.


cirriform

Clouds composed mostly or entirely of small ice crystals, usually transparent and white; often producing halo phenomena not observed with other cloud forms. Cirriform clouds include cirrus, cirrocumulus, and cirrostratus clouds. The average height of cirriform clouds ranges upward from about 20,000 ft (6,096 m) in the middle latitudes.


cirrocumulus

A cirriform cloud appearing as a thin sheet of small white puffs resembling flakes or patches of cotton without shadows; sometimes confused with altocumulus.


cirrostratus

A cirriform cloud appearing as a whitish veil, usually fibrous, sometimes smooth. Cirrostratus clouds often produce halo phenomena and may totally cover the sky.


cirrus clouds

Feathery, high-altitude clouds composed of ice crystals. Cirrus clouds typically form in shallow scattered to broken layers on the equatorial side of the jet stream when high level moisture is available. They indicate very strong upper winds. Cirrus clouds do not in themselves constitute a hazard to aircraft, but they should alert pilots to the possibility of high-altitude turbulence and the approach of developing or intense weather systems.


Clarence "Kelly" Johnson

1910–1990. American airplane designer, head of Lockheed's Advanced Project Development Group for 30 years. Johnson, known as the "King of the Skunk Works" at Lockheed, made major contributions to the development of more than 40 airplane models, including the Electra, the Constellation, the U-2 spyplane, and the SR-71 Blackbird.


class (aircraft)

With respect to the certification of aircraft, a broad grouping of aircraft with similar characteristics of propulsion, flight, or landing. In the U.S., the FAA recognizes the following classes of aircraft: airplanes, rotorcraft, gliders, balloons, landplanes, and seaplanes.

With respect to the certification of pilots, a grouping of aircraft with similar operating characteristics; for example, single engine, multiengine, land, water, and helicopter.


class (pilot rating)

A classification of aircraft used on pilot certificates and ratings. In this respect, "class" means aircraft with similar operating characteristics; for example, single engine, multiengine, land, water, helicopter, and so forth.


Class A airspace

In the U.S., the airspace extending from 18,000 ft (5,486 m) above mean sea level up to and including flight level 600 (approximately 60,000 ft [18,288 m]). Formerly known as "positive control airspace (PCA)." All operations in Class A airspace are conducted according to instrument flight rules (IFR) under direct air traffic control. Class A airspace is not marked on aeronautical charts.


Class B airspace

In the U.S., the airspace around the busiest major terminals. Formerly called a "terminal control area (TCA)," Class B airspace is typically arranged in rings centered on the primary airport. The innermost ring usually extends from the surface up to 10,000 ft (3,050 m). The next rings each begin at different intermediate altitudes to allow non-airline traffic to transit the area beneath the Class B airspace and operate at satellite airports. This stair-step arrangement, drawn in cross-section, makes Class B airspace look like an inverted wedding cake.

All aircraft operating in Class B airspace must receive a clearance from air traffic control, regardless of current weather conditions. Aircraft must also have transponder with automatic altitude reporting capability. The boundaries of Class B airspace are marked with solid blue lines on U.S. aeronautical charts.


Class C airspace

In the U.S., the airspace around airports that have an operating air traffic control tower, radar approach control, and a high level of IFR operations or airline traffic. Class C airspace is typically designated around second-tier airports that are not as busy as major terminals. Many military airports are also surrounded by Class C airspace.

Class C airspace is typically arranged in two rings centered on the primary airport. The innermost ring has a typical diameter of 5 nm and generally extends from the surface up to 4,000 ft (1,220 m). The next ring begins at 5 nm from the center and extends to 10 nm. It begins at 1,200 ft (365 m) above the airport elevation and extends to 4,000 ft (1,220 m). Class C airspace also includes an outer area, which extends to 20 nm from the primary airport.

All aircraft operating in Class C airspace must establish communications with air traffic control, regardless of current weather conditions. Aircraft must also have transponder with automatic altitude reporting capability (Mode C). The boundaries of Class C airspace are marked with solid red lines on U.S. aeronautical charts.


Class D airspace

In the U.S., the airspace around an airport that has an operating air traffic control tower. Class D airspace is typically a circle centered on the airport, with a diameter of about 5 miles. It typically extends from the surface to 2,500 ft (762 m) above the airport elevation. Class D airspace often includes extensions to ensure that the controlled airspace encloses instrument approaches.

All aircraft operating in Class D airspace must establish communications with the air traffic control tower, regardless of current weather conditions. The boundaries of Class D airspace are marked with dashed blue lines on U.S. aeronautical charts.


Class E airspace

Generally, in the U.S., controlled airspace not designated as Class A, B, C, or D. Class E airspace includes low-altitude airways, extensions to Class D airspace, transition areas, and other airspace where air traffic control clearances are required when the ceiling and visibility do not meet the minimums for operations under visual flight rules (VFR).

Class E airspace typically begins at either 700 ft (213 m) or 1,200 ft (365 m) above the surface. It extends upward to the base of any overlying controlled airspace. When designated as an extension to Class D airspace, Class E airspace begins at the surface. Aircraft operating in Class E airspace must establish communications with the air traffic control tower only when operating under instrument flight rules (IFR). The boundaries of Class E airspace are marked with dashed red lines or with shaded red or blue lines on U.S. aeronautical charts.


Class G airspace

In the U.S., airspace not designated as Class A, Class B, Class C, Class D, or Class E airspace. Class G airspace typically begins at the surface and extends upward to either 700 ft (213 m) or 1,200 ft (365 m) above ground level (AGL). The boundaries of Class G airspace are not explicitly marked on U.S. aeronautical charts.


clear air turbulence (CAT)

Turbulence in an area where no clouds are present; in particular, turbulence at high altitude. CAT is also sometimes used to describe turbulence associated with wispy cirrus clouds. Many phenomena can generate CAT. It is often associated with the jet stream, especially in winter when temperature contrast is greatest between cold and warm air. CAT also occurs in wind shears associated with sharply curved contours of strong lows, troughs, and ridges aloft, mountain waves, and areas of strong cold or warm air advection.


clear ice

Relatively transparent ice with a homogeneous structure and few, small air spaces. Clear ice is usually associated with large, supercooled water drops typically found in cumuliform clouds. Clear ice forms when the liquid portion of a drop flows out over the aircraft surface before it freezes. Clear ice is hard, heavy, and difficult to remove.


cloud layer

In Flight Simulator, a user-specified weather option that includes the type of cloud, the heights of the bases and tops of the clouds, visibility, turbulence, and whether icing conditions exist. You select these options in the Advanced Weather dialog box. You can create two cloud layers in each weather area.


Clyde Cessna

1880–1954. American aviation pioneer and aircraft manufacturer. Inspired by the Moisant International Aviators' air circus, Cessna built his own monoplane and became a barnstormer. Later, he teamed up with Walter Beech and Lloyd Stearman in the Travel Air Manufacturing Company before forming the Cessna Aircraft Company in 1927. Cessna retired in 1935, handing the reins to his nephew, Dwane Wallace.


col

In meteorology, the neutral area between two highs and two lows or the intersection of a trough and ridge. The col on a pressure surface is analogous to a mountain pass on a topographic surface.


cold front

Any non-occluded front that moves in such a way that colder air replaces warmer air.


collective

On a helicopter, the lever to the left of the pilot’s seat that controls the lift produced by the main rotor. Pulling up on the collective increases the pitch of all of the main rotor blades. As the pitch of the blades increases, they produce more lift. Lowering the collective decreases the pitch of all the main rotor blades, decreasing the lift they produce. The throttle is mounted on the end of the collective.

A helicopter pilot can hold a constant altitude by adjusting the collective. The actual position of the collective required to maintain altitude depends on the helicopter’s weight, density altitude, airspeed, and other factors.

You must use the collective in conjunction with the cyclic and anti-torque pedals. Raising the collective increases torque from the main rotor, so you must add left pedal to keep the helicopter’s nose from rotating to the right. Lowering the collective decreases main rotor torque, so you must apply right pedal to keep the helicopter’s nose from rotating to the left. As you move the collective you must also use the cyclic to maintain the helicopter’s position.


COM

Abbreviation for "communication"; usually refers to radio communication. Aircraft communications radios are typically labeled "COM1," COM2," and so forth.


commercial pilot certificate

In the U.S., a pilot certificate that allows a person to act as pilot in command of an aircraft for compensation or hire. To be eligible for a commercial pilot certificate, a person must be at least 18 years old and hold a current second class medical certificate and a private pilot certificate. The applicant must have at least 250 hours of flight time, including at least 10 hours of instruction in an aircraft with a controllable pitch propeller, flaps, and retractable landing gear. The applicant also must have at least 50 hours of cross-country flight time and meet other experience and knowledge standards.


composites

Materials consisting of glass or carbon fibers set in a matrix of plastic or epoxy resin. Composites are increasingly used in the construction of modern aircraft because they are strong and lighter than metals. Many new kit-built and experimental aircraft are built primarily out of composites.


condensation

The change of water vapor to liquid water.


condensation trail

A cloud-like streamer that frequently forms behind aircraft flying in clear, cold, humid air. Condensation trails are also called "contrails" and "vapor trails."


contra-rotating
contra-rotating propellers

A pair of propellers, mounted one behind the other on the same engine, that rotate in opposite directions. Contra-rotating propellers make more efficient use of the power from the engine and counteract the gyroscopic and aerodynamic forces generated by a single large propeller turning in one direction. The principle was first applied to an Italian Macchi-Castoldi racing plane in 1933.


control yoke

The steering-wheel-like control that is connected to the ailerons and elevator. A pilot turns the yoke to move the ailerons and bank the wings. The pilot moves the yoke forward and back to move the elevator, which lowers and raises the nose. Some airplanes have a stick or "joystick" instead of a control yoke.


controlled airport

An airport with an operating control tower. You must obtain a clearance to take off or land at a controlled airport, and follow the tower controller's instructions while operating on or around a controlled airport. Controlled airports are usually located within Class B, Class C, or Class D airspace. The basic rules for operating at an airport with a control tower are contained in FARs 91.131, 91.130, and 91.129 and in the Aeronautical Information Manual (AIM).


controlled airspace

In the U.S., airspace in which operations may require a clearance from air traffic control (ATC), especially when a low ceiling or restricted visibility requires aircraft to operate under instrument flight rules (IFR). Controlled airspace is divided into several classes (A, B, C, D, E, and G) according to standards established by ICAO. Each class has different operating rules, including requirements for communications with ATC, specific clearances from ATC, pilot qualifications, aircraft equipment, maximum operating speeds, and minimum ceiling and visibility for operations under visual flight rules (VFR).


convection

In meteorology, atmospheric motions that are predominantly vertical, resulting in vertical transport and mixing of atmospheric properties.


convective clouds

Clouds exhibiting vertical development; cumuliform clouds. Convective clouds form in air that is moving primarily upward rather than horizontally.


coordinated flight

Flight, especially during turns, in which the horizontal and vertical forces at work on the airplane are in balance. The inclinometer, part of the turn coordinator or "needle and ball," shows the pilot whether the aircraft is in coordinated flight. When the ball moves to the inside of a turn, the airplane is "slipping"—the angle of bank is too steep for the rate of turn. If the ball moves to the outside of a turn, the airplane is "skidding"—the rate of turn is too great for the angle of bank. Uncoordinated flight can also occur during flight at low airspeed if the pilot does not apply enough rudder to compensate for the yaw force created by the propeller and engine at high power settings.


Coriolis force

A deflective force resulting from earth's rotation. In the northern hemisphere, the Coriolis force deflects moving air to the right. In the southern hemisphere, the force deflects moving air to the left. The force acts at a right angle to wind direction and is directly proportional to wind speed. That is, as wind speed increases, Coriolis force increases. At a given latitude, double the wind speed and you double the Coriolis force. Coriolis force also varies with latitude, from zero at the equator to a maximum at the poles. It influences wind direction everywhere except immediately at the equator; but its effects are most pronounced in middle and high latitudes.


Count Ferdinand von Zeppelin

1838–1917. German aeronaut, inventor, and army general who rode in observation balloons with Union forces during the American Civil War. In 1898 he founded an airship factory in Germany and constructed the first rigid type of airship. By 1910 his zeppelins carried passengers on excursions between German cities, and in 1912 the German navy ordered the first military zeppelin.


course deviation indicator
course deviation indicator (CDI)

A vertical needle on the omni-bearing indicator (OBI) that shows your deviation from the very high frequency omnidirectional range (VOR) radial set by the course selector. If the needle is to the right of center, the radial lies to the right of your current position.


course selector (OBS)

The knob or other control a pilot uses to select a VOR radial. Also known as the "omni bearing selector (OBS)."


crab angle

The angle between an aircraft's heading and ground track. This angle is determined by the crosswind component and the airspeed of the aircraft; the stronger the crosswind and the lower the airspeed, the larger the aircraft's crab angle.


critical angle of attack

The angle of attack at which a wing stalls. The critical angle of attack is determined by the airfoil design. A wing always stalls when it reaches its critical angle of attack, regardless of the aircraft's airspeed or attitude. Most general aviation aircraft have wings with a critical angle of attack of 18–20 degrees.


cruise speed

The average speed of an aircraft during straight and level flight at normal power settings.


cumuliform

A descriptive term applied to all convective clouds that develop vertically rather than into horizontally extended stratiform types. Cumuliform clouds develop in unstable air.


cumulonimbus clouds

Dense, vertical cloud formations that usually produce heavy rain, thunderstorms, or hailstorms. "Cumulus" is from the Latin for "heap"; "nimbus," for "rain cloud." Like all cumuliform clouds, cumulonimbus form in unstable air. A cumulonimbus cloud is heavy and dense. It can have massive towers, often with tops in the shape of an anvil or plume. Cumulonimbus clouds are often associated with virga, precipitation and low ragged clouds (scud), lightning, thunder, and sometimes hail. They occasionally produce a tornado or a waterspout. Cumulonimbus clouds can extend well into the stratosphere.


cumulonimbus mamma

A cumulonimbus cloud having hanging protuberances, like pouches, festoons, or udders, on the underside of the cloud. It is usually indicative of severe turbulence.


cumulus clouds

Fluffy, flat-based clouds, formed by rising, unstable air. "Cumulus" is from the Latin for "heap." Cumulus clouds are usually dense and well defined. They develop vertically in the form of rising mounds; the bulging upper part often resembles a cauliflower. Sunlit parts of these clouds are mostly brilliant white; their bases are relatively dark and nearly horizontal.


cyclic

On the helicopter, the stick that controls the aircraft’s attitude, direction of movement, and airspeed. The cyclic is linked mechanically to the main rotor system. As you move the cyclic, the entire rotor disk tilts.

Moving the cyclic forward tilts the rotor disk toward the front of the helicopter. The nose lowers and the helicopter moves forward. Moving the cyclic back causes the nose to rise and makes the helicopter move backward. Likewise, moving the cyclic left or right causes the helicopter to bank and turn, much like an airplane.

You should use the cyclic to turn a helicopter, except in a hover.

In a hover, moving the cyclic causes the helicopter to translate, or move across the ground, in the direction that the cyclic was moved and at a speed proportional to how far the cyclic was moved.


cyclone
cyclone (low)

An area of low atmospheric pressure with a closed, cyclonic circulation. Viewed from above, the circulation is counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere, and undefined at the equator. Because cyclonic circulation and relatively low atmospheric pressure usually coexist, in common practice the terms "cyclone" and "low" are used interchangeably. Also, because cyclones often are accompanied by inclement (sometimes destructive) weather, they are frequently referred to simply as storms. "Cyclone" is frequently misused to denote a tornado.


Daniel Bernoulli

1700–1782. Swiss scientist. His most important discovery, known as "Bernoulli's principle," states that the total energy of fluid in motion remains constant: if its speed increases, its pressure drops; if its speed decreases, its pressure increases. This principle was important to early scientists studying airflow, and their applications led to the design of wings capable of lifting heavier-than-air craft off the ground.


datum

An imaginary vertical plane or line used as a reference in weight-and-balance calculations; specifically the line from which all "arm" measurements are taken. The center of gravity (CG) is often referenced from the datum. The aircraft manufacturer sets the datum for a particular airplane. Most manufacturers set the datum at the position of the firewall separating the engine from the passenger compartment or at the tip of the propeller spinner.


dead reckoning
dead reckoning (ded reckoning)

The navigation of an airplane solely by computations based on airspeed, course, heading, wind direction and speed, ground speed, and elapsed time. The term derives from "deduced" reckoning. Also known as "ded reckoning."


decision height
decision height (DH)

The altitude at which, during an ILS or other precision landing approach, a pilot must decide whether to land or execute a missed approach. A typical ILS approach has a DH of 200 ft (60 m) above ground level.


density altitude

Pressure altitude corrected for variations from standard temperature. Density altitude measures the actual density of the air, and therefore is a critical factor in calculating aircraft performance. If the temperature is warmer than standard, density altitude is higher than pressure altitude, and vice versa. For example, assume an airport is 3,000 ft (914 m) above sea level and the altimeter setting is 29.92 (1013.2 millibars). If the temperature is 90 degrees F (32 degrees C), the density altitude is 5,592 ft (1,704 m). An airplane taking off from this airport performs as if it's at nearly 5,600 ft (1,705 m). The engine produces less power, the propeller is less efficient, and the wings create less lift. The airplane uses more runway to reach takeoff speed and climbs at a lower rate.


detonation

The sudden, explosive burning of the air/fuel mixture in the cylinders of a piston engine. Detonation usually occurs when the air/fuel mixture is too lean—when there is not enough fuel for the current weight of air entering the cylinder. Detonation imposes excessive loads on the pistons and other engine components. If not corrected by enriching the mixture, detonation causes engine damage and may lead to sudden engine failure.


dew

Water condensed onto grass and other objects near the ground when the temperature of those objects has fallen below the initial dew point of the surface air but is still above freezing.


dew point

The temperature to which air must be cooled to reach saturation—100 percent relative humidity. Weather reports usually include the air temperature and dew point temperature. A narrow "temperature/dew point spread" (less than 5 degrees F or 2.8 degrees C) indicates a strong likelihood of fog, clouds, or precipitation.


dihedral

The angle at which an aircraft's wings tilt upward from the fuselage forming a slight "V" shape as seen from head-on. Dihedral increases stability about the longitudinal or roll axis of an airplane. It tends to level the wings after an airplane is established in a shallow bank. Anhedral, tilting the wings downward, produces the same effect, but it is much less common.


dirigible
dirigibles

A general term for airships, or lighter-than-air powered aircraft. An engine and the ability to steer distinguishes airships from balloons. From the Latin dirigere, "to direct."


disk cache

An information storage area. Flight Simulator stores scenery information in a cache directory on your hard drive for quick access as you fly.


dissymmetry of lift

In a helicopter, a condition in which the main rotor does not produce lift equally across the entire rotor disk. Dissymmetry of lift is most apparent during a retreating blade stall, in which the left half of the rotor disk (as seen from above) is stalled due to the helicopter’s high forward speed, high gross weight, high density altitude, low rotor RPM, turbulence, abrupt use of controls, or steep turns. This effect is present only when the helicopter is in forward flight or hovering in a wind. Designers can compensate for dissymmetry of lift by allowing the blades to flap.


distance measuring equipment
distance measuring equipment (DME)

Avionics that determine and display distance in nautical miles. DME equipment, which operates in the UHF band, is usually installed at a VOR station. A complementary unit installed in the aircraft transmits timed pulses to the ground station, which replies. The unit in the aircraft converts the time between the pulses and the replies into distance and also derives ground speed and time to reach the station. The distance displayed by DME equipment is the "slant range" from the station—the length of the hypotenuse of a right triangle formed by the aircraft's altitude and its distance from the station as measured along the ground. The difference between the slant-range and the aircraft's actual distance from the station is negligible when the aircraft is more than about 10 nm from the station and at a moderate altitude.


downdraft

A relative small-scale downward current of air often observed on the lee side of large objects that restrict the smooth flow of the air, or in precipitation in or near cumuliform clouds.


drag

The resistance of an object to movement through a fluid. With respect to aircraft, drag is one of the four fundamental forces in flight. It opposes thrust. There are two basic types of drag. Parasite drag is caused by friction. The airplane surface, antennas, landing gear, and other appendages all cause parasite drag, which increases in proportion to the square of the aircraft's velocity. Induced drag is a byproduct of lift. At the tip of a wing, air moves from the high-pressure area below the wing to the low-pressure area above. The energy used to create these vortices manifests itself as induced drag, which increases as airspeed drops.


drift

The displacement of an aircraft from its intended course caused by wind.


drizzle

A form of precipitation composed of very small water drops that appear to float with the air currents while falling in an irregular path. Drizzle differs from rain, which falls in a comparatively straight path, and fog droplets, which remain suspended in the air. In weather reports and forecasts, drizzle is indicated by the abbreviation "DZ." On weather charts in the U.S., drizzle is indicated by a comma (,).


dry adiabatic lapse rate

The rate of decrease of temperature with height when unsaturated air is lifted adiabatically (due to expansion as it is lifted to lower pressure).


effective translational lift
effective translational lift (ETL)

In a helicopter, a large increase in performance while in forward flight or when hovering in a wind. Air moving horizontally across the rotor disk helps the rotor produce more lift at a given power setting. This effect is generally seen at speeds of 10–15 knots. The transition to ETL is marked by a low-frequency vibration. The helicopter’s nose rises and the aircraft begins to climb vertically.


electronic flight instrument system (EFIS)

Computer-driven cockpit instruments and displays that replace electro-mechanical instruments in many modern flight decks. The EFIS can display basic flight information, engine status, moving maps, checklists, and other information.


elevator

A movable control surface located on the horizontal stabilizer of an aircraft's empennage, or tail. Although its name implies that the elevator makes the airplane climb or descend, it actually controls only the aircraft's pitch attitude—the angle of the nose above or below the horizon. The pilot moves the elevator by applying forward pressure on the control yoke or stick to decrease pitch attitude and by applying back pressure to increase the pitch attitude. On some aircraft, the entire horizontal stabilizer moves. This arrangement is often called a "stabilator" or "flying tail."


empennage

The tail assembly of an airplane. The empennage usually includes the fin (vertical stabilizer), rudder, horizontal stabilizer, and elevator.


Flight Watch
EFAS (Flight Watch)

Shorthand for Enroute Flight Advisory Service, a weather service provided in the U.S. by Flight Service Stations. EFAS disseminates weather reports and forecasts, particularly en route weather, and receives and distributes pilot reports (PIREPS). Flight Watch is available throughout the U.S. on frequency 122.0 from 5,000–17,500 ft (1500–5000 m) and on a variety of discreet frequencies for high-altitude traffic.


Ernst Mach

1838–1916. Austrian physicist and member of the Austrian Parliament. Mach's writings on empirical methodology and his theories on sensation and perception established the study of the philosophy of sciences. His work in ballistics and on measuring the speed of sound contributed greatly to the branch of aerodynamics concerned with supersonic flight.


Experimental Aircraft Association (EAA)

One of the largest aviation organizations in the world, the EAA was started in 1953 by Paul Poberezny and several other aviation enthusiasts as a club for people who build their own airplanes. The first fly-in convention that same year attracted about 40 people. Today the EAA numbers more than 150,000 members around the world and brings more than 800,000 people each year to its Oshkosh Fly-In, including homebuilders, restorers of classic and antique aircraft, and warbird enthusiasts.


Federal Aviation Administration (FAA)

In the U.S., the federal government agency responsible for the regulation and promotion of aviation. The FAA regulates and certifies pilots, aircraft, airports, and airspace. It also manages the air traffic control system and supervises and inspects airlines, flight schools, flight instructors, maintenance technicians and facilities. The FAA was created in 1958 to supersede the Civil Aeronautics Authority (CAA). It operated under the name Federal Aviation Agency until 1966, when it became the Federal Aviation Administration, an organization within the Department of Transportation.


Federal Aviation Regulations (FARs)

In the U.S., the parts of the Code of Federal Regulations that pertain to the certification and regulation of pilots, flight schools and instructors, maintenance technicians and facilities, aircraft, air navigation, airspace, air traffic control, and other activities related to aviation and air commerce. Pilots must be familiar with and adhere to a variety of FARs. The most important parts of the FARs for day-to-day operations are: Part 1, Definitions and Abbreviations; Part 61, Certification: Pilots and Flight Instructors; and Part 91, General Operating and Flight Rules. Other parts pertain to commercial and airline operations, certificated flight schools, transportation of hazardous materials, certification standards for aircraft, and procedures for reporting accidents.


fixed base operator
fixed base operator (FBO)

At an airport, a person or an organization that sells fuel, sells or rents aircraft, and possibly provides flight instruction.


flaps

A hinged portion of an airplane's wing, generally on the trailing edge, that can be swung downward during takeoff and landing to increase the wings' lift and drag. When partially extended, a flap adds lift by increasing the camber, or curvature, of the wing. Because flaps extend into the oncoming air, they also increase drag, helping an aircraft descend steeply without building up speed. Modern aircraft use several types of flaps; the most common designs are plain, split, and Fowler. Often confused with ailerons, flaps are not primary control surfaces of an airplane.


flare

To level off and establish the correct landing attitude just above the runway prior to landing. A pilot flares by applying back pressure to the control yoke or stick, which raises the nose of the aircraft. When done properly, the flare is a smooth, continuous transition from a nose-low, descending flight path to a nose-high attitude that almost stops the aircraft's descent.


fractus

Clouds in the form of irregular shreds. They have a torn, clearly ragged appearance. The term applies only to stratus and cumulus cloud types such as cumulus fractus and stratus fractus.


freezing level

A level in the atmosphere at which the temperature is 32 degrees F (0 degrees C).


front

The boundary between two different air masses. More specifically, a surface, interface, or transition zone of discontinuity between two adjacent air masses of different densities.


frontal zone

A front or zone with a marked increase of density gradient. The term is used to describe an area of rapid transition of meteorological elements.


frontogenesis

The initial formation of a front or frontal zone.


frontolysis

The dissipation of a front.


fly-by-wire
fly-by-wire controls

Electronic flight control system in which there are no direct mechanical links between the controls in the cockpit and the aircraft's control surfaces. A computer detects movements of the flight controls, interprets them, and sends signals to move the rudder, ailerons, and elevators. Fly-by-wire systems were first used in fighter aircraft to make aircraft more maneuverable and ensure that the pilot could not exceed the design limitations of the aircraft. Today, large transports such as the Boeing 777 and several Airbus models include fly-by-wire systems.


Frank Whittle

1907–1996. English engineer and RAF officer who invented the turbojet aircraft engine. Whittle published his theory of jet propulsion in 1928, but the British Air Ministry didn't become interested in the idea until 1938. Whittle developed a working jet aircraft by 1941; however, it wasn't until 1944 that the first military jet aircraft, the Gloster Meteor, was put into service.


Flight Service Station (FSS)

A government facility that provides a variety of services to pilots. FSS personnel take weather observations, brief pilots, coordinate flight plans, and assist aircraft in distress. In the U.S., the FSS network includes one or more stations in each state. Each FSS typically has responsibility for a large geographic area. FSS specialists communicate with pilots over a network of remote transmitters and receivers. They also have direct telephone and computer connections to air traffic control facilities and search-and-rescue organizations.


fuel injection system

A set of controls, pumps, nozzles, and other components used in many piston engines to deliver fuel to the cylinders. The system squirts fuel directly into the cylinders or just ahead of the intake valve, where it mixes with air. Because a fuel injection system requires high-pressure pumps, an air/fuel control unit, fuel distributor, and discharge nozzles for each cylinder, it's generally more expensive than a carburetor. But a fuel injected engine is more efficient than a carburetor, and fuel injection is used on most large piston engines.


fully articulated rotor system

One of three main types of rotor systems used in modern helicopters. A fully articulated rotor system has three or more main rotor blades. The blades flap—move up and down—independently to compensate for dissymmetry of lift. They also feather—twist at the rotor hub—independently to adjust angle of attack as they rotate and lead and lag independently to compensate for the Coriolis force.

Fully articulated rotor systems are more expensive to manufacture and maintain than semi-rigid rotors, but they are less susceptible to low G conditions and mast bumping. However, they are more affected by ground resonance.


fuselage

The body of an airplane that holds the crew and passengers or cargo. From the French fuselé, for "spindle-shaped."


Gs

A measurement of the load factor, or apparent gravity, experienced by an aircraft during flight. One G represents the force of gravity exerted on a body at rest. When an aircraft climbs, turns, or changes speed, it experiences G forces. For example, a level turn with a 60-degree bank imposes a 2G load on an airplane and its occupants.


general aviation (GA)

In the U.S., a term applied to all aviation not related to the military or scheduled airline service. It includes flight training, charter flights, flying for pleasure, and business-related aviation. The term is also used to describe a broad class of aircraft not used by the military or scheduled airlines. "General aviation" is sometimes abbreviated "GA."


glide ratio

Ratio of horizontal distance traveled per unit of descent. For example, a sailplane with a 60:1 glide ratio travels 60 meters forward for every 1 meter it descends. A typical single-engine aircraft has a glide ratio of about 10:1.


glide slope

The electronic approach path projected as part of an Instrument Landing System (ILS). Glide slope transmitters, located near the end of a runway, send out radio signals to form the proper descent path to the runway. The angle of the glide slope is usually set about three degrees to the horizontal.


Greenwich Mean Time (GMT)

The local time at the Greenwich Observatory, which lies on the prime meridian or 0 degrees longitude. This time, now known officially as coordinated universal time (UTC), is used in air navigation to provide a standard for proposed departure and arrival times, weather observations and forecasts, and air traffic control functions. Also known as Zulu time, UTC is expressed in 24-hour format; for example, 6:00 P.M. is 1800 hours.


ground effect

A decrease in induced drag as an aircraft flies near the surface. In an airplane, the effect is caused when the ground interferes with the normal flow of air from below the wing to the low-pressure area above the wing. Ground effect is most apparent when an airplane’s height is about one-half wingspan or less above the surface. In practical terms, an airplane flying in ground effect stalls at lower airspeed than normal. Pilots can use ground effect to lift off from a soft or short field with a minimum ground roll, but they must accelerate to normal flying speed before climbing away from the surface.

In a helicopter, ground effect is defined as an increase in performance when the helicopter is within one rotor span of the ground. It is most apparent when the main rotor disk is within one-half the rotor span of the ground—that is, a 3-foott (1 m) hover in the Bell 206B JetRanger III. As in an airplane, ground effect occurs when the ground interferes with the vortices produced at the ends of the main airfoil—in this case, the rotor-tip vortices. The ground also reduces the acceleration of the induced flow—the air pulled down and through the rotor disk. The decreased downward velocity of the induced flow makes a given pitch angle more effective at producing lift. While in ground effect, the helicopter requires less power to hover.


ground fog

In the U.S., a fog that conceals less than 0.6 of the sky and is not contiguous with the base of clouds.


ground loop

An aggravated, uncontrolled, tight turn on the ground, usually during rollout after landing or while taxiing. A ground loop often involves a turn of more than 90 degrees and frequently results in one wing touching the ground. Aircraft with tailwheels (taildraggers) are most susceptible to this loss of control because the center of gravity in such aircraft lies behind the main landing gear.


ground speed

An aircraft's speed relative to the ground; an aircraft's true airspeed corrected for the effects of a headwind or tailwind. For example, if an aircraft is flying level at 120 knots with a 15-knot headwind, its ground speed is 105 knots.


GUMPS check

A memory aid to help pilots check critical items before landing. The letters of this acronym usually stand for:

G: Gas; check that fuel selector is set on fullest tank or “Both.”

U: Undercarriage (landing gear); check that landing gear is down and locked.

M: Mixture; check that mixture control is set to full rich.

P: Prop/Pumps; check that propeller control is set to full increase (maximum RPM); check that auxiliary fuel pump is on, if applicable.

S: Seatbelts; check that seat belts and shoulder harnesses are fastened and adjusted.

There are many variations of this basic memory aid. Some pilots add letters or substitute other items for the letters in this acronym.

The CIGAR check is a similar mnemonic to help pilots remember to check critical items before takeoff.


gust

A sudden brief increase in wind. In weather reports and forecasts, gusts are indicated by "G" followed by the two- or three-digit maximum speed and units, usually knots (KT). For example, "G25KT" indicates wind gusting to a maximum of 25 knots.


gyro

Short for gyroscope, an instrument based on a free-spinning wheel mounted within a ring. Gyros are used in instruments such as the attitude indicator, heading indicator, and turn coordinator. Because a spinning gyro maintains its orientation even when an airplane banks, climbs, or dives, it provides a stable reference to help pilots control an aircraft while flying in clouds or poor visibility.


gyroscopic precession

The reaction of a gyro when a force is applied to the spinning wheel. When force is applied to a gyro, the device reacts as if the force had been applied at a point 90 degrees from the point of actual application, in the direction of rotation. Precession affects propellers, which act like gyros, and gyro instruments. Its principle effect is on the heading indicator, which tends to drift over time.


hail

Frozen precipitation often associated with thunderstorms. Hail forms when supercooled water droplets begin to freeze. After a drop has frozen, other drops latch on and freeze to it. The hailstone grows—sometimes into a huge iceball. As hailstones fall through warming air, they begin to melt, and precipitation may reach the ground as either hail or rain. Rain at the surface does not mean the absence of hail aloft. You should anticipate possible hail with any thunderstorm, especially beneath the anvil of a large cumulonimbus. In weather reports and forecasts, hail is denoted by the abbreviation "GR," from the French grêle.


heading

The direction in which the aircraft is pointed, usually referenced to magnetic north. Because wind pushes an airplane in flight, heading does not necessarily correspond to the aircraft's path over the ground—its track. For example, if you want to fly due east with respect to the ground and the wind is blowing from the north, you must turn the aircraft slightly into the wind to correct for drift.


heading indicator

A gyro instrument that accurately and quickly shows changes in aircraft heading. Sometimes called the "directional gyro" or "DG." Because the heading indicator is driven by a gyro, it provides smooth, precise indication of heading or turns. The compass, which is subject to acceleration, deceleration, dip, and other errors, often oscillates, leads, or lags a turn. However, because gyros are affected by precession, the pilot must periodically set the heading indicator to correspond to the compass (unless the heading indicator is "slaved" electronically to the compass).


high

An area of high barometric pressure. Also called an anticyclone or high pressure system.


high-performance aircraft
high-performance airplane

As defined in FAR 61.31(e), an airplane that has more than 200 horsepower or that has retractable landing gear, flaps, and a controllable propeller. A private or commercial pilot may not act as pilot in command of a high-performance airplane unless a flight instructor has certified that the pilot is competent to fly such aircraft.


hood

A view-limiting device worn by pilots who are learning or practicing flight by instruments. The hood covers the upper portion of the pilot's field of vision. A safety pilot or instructor must always accompany a pilot who is using a hood.


horizontal situation indicator (HSI)

An instrument that combines the functions of the heading indicator and a VOR and ILS display. The HSI is usually mounted directly below the attitude indicator. It shows a “bird’s eye” view of the aircraft’s position relative to a selected VOR or ILS localizer course. Indicators on one or both sides of the display show the aircraft’s position relative to an ILS glide slope. In aircraft with electronic flight instruments, the pilot can often switch between several HSI display modes.


horizontal stabilizer

The horizontal surface of the tail, or empennage. The horizontal stabilizer is an airfoil that creates a down force on the tail to balance the upward force generated by the wing. It also incorporates the elevator, the control surface used to adjust the aircraft's pitch attitude. On some airplanes, the entire horizontal stabilizer acts as an elevator.


hover

In a helicopter, to remain stationary over a point on the ground at a constant altitude. A helicopter can hover in ground effect—within about one-half its rotor span of the ground—or out of ground effect. The helicopter’s ability to hover depends on its weight, power available, and the density altitude.


hover taxi

In a helicopter, to move short distances at airspeeds less than about 20 knots and at an altitude of 25 ft (8 m) or less.


hypersonic

Speeds at or above Mach 5—five times the speed of sound.


hypoxia

A condition in which an insufficient amount of oxygen reaches the tissues of the human body. The complete lack of oxygen, called anoxia, is fatal. Hypoxia is a serious hazard at high altitudes, particularly because its warning symptoms are varied and sometimes difficult to detect. Cabin pressurization or oxygen equipment is generally necessary for flying at altitudes at or above about 10,000 ft (3,048 m).


ICAO

Abbreviation for the International Civil Aviation Organization. ICAO, based in Montreal, sets international standards for airports, pilots, communications, and other matters related to air transportation.


Igor Sikorsky

1889–1972. Russian-born aircraft designer and manufacturer, considered "the father of the helicopter." Sikorsky built his first helicopter at age 20, and in 1913 he built the world's first four-engine airplane. After moving to the U.S. in 1919, he formed an aircraft company with other Russian émigrés. Sikorsky's flying boats, although technical successes, were a financial failure, so with support from United Air Transport, he returned to helicopters. In 1939 his VS-300 became the first practical helicopter.


Immelmann

An aerobatic maneuver in which an airplane reverses its direction of flight while gaining altitude. The maneuver begins with a half loop. Said to have been invented by WWI ace Max Immelmann. At the top of the loop, the pilot rolls the plane upright. In modern aerobatic competitions an Immelmann is called a "half loop, half roll."


indefinite ceiling

A ceiling classification that describes vertical visibility into a surface-based obscuration.


indicated airspeed (IAS)

The speed shown on the airspeed indicator, uncorrected for variations in atmospheric density, installation error, or instrument error. Except at sea level under standard atmospheric conditions, IAS does not correspond to the aircraft's actual speed through the surrounding air (that is, its true airspeed, or TAS).

By default, airspeed indicators in Microsoft Flight Simulator display indicated airspeed. You can change this setting to display true airspeed on the airspeed indicators. Click Preferences on the Options menu, and on the Instrument tab, clear the Display Indicated Airspeed option.


indicated altitude

Altitude read directly from the altimeter after it is set to the local barometric pressure corrected to sea level. Indicated altitude is not corrected for temperature. Pilots use indicated altitude to control their aircraft.


induced drag

The portion of total drag created by lift. Induced drag is created when high-pressure air below a wing or rotor swirls around the tip to the low-pressure area above. This motion creates vortices, which in effect siphon off the aircraft's energy. This lost energy is induced drag. Induced drag increases as airspeed decreases.


infrared

Electromagnetic radiation with wavelengths beyond the red end of the visible color spectrum. Infrared photography, used in aerial surveillance, can penetrate haze and clouds to capture images of objects that are not visible to the naked eye.


instrument approach procedure (IAP)

An official procedure designed to guide aircraft to a runway when a visual descent isn't possible. IAPs describe the route and altitude aircraft are to fly as they transition from en route flight to landing. There are two basic types of instrument approach procedures—nonprecision and precision. Nonprecision approaches do not have an electronic glide slope to provide vertical guidance to landing aircraft. Examples of nonprecision approaches include VOR, NDB, localizer, and GPS approaches. Precision approaches have electronic glide slopes that provide precise vertical guidance. The most common precision approach is the ILS.


instrument flight rules (IFR)

In the U.S., regulations that apply to pilots, aircraft, and aircraft operations when weather conditions do not meet the criteria for visual flight, when aircraft are operated in Class A airspace—that is, at altitudes at and above 18,000 ft (5,486 m), or when pilots choose to operate in controlled airspace under those rules regardless of the prevailing weather. The rules establish minimum fuel reserves, equipment requirements and checks, and other operational standards for instrument flight.

The abbreviation IFR is sometimes used to describe weather that doesn't meet the minimums established for flight under visual flight rules (VFR). For example, if an air traffic controller alerts a pilot to nearby traffic and the pilot is flying in the clouds, the pilot may say, "I'm IFR," and ask for a change in heading or altitude to avoid a conflict. The proper abbreviation for describing those conditions is "IMC," for "instrument meteorological conditions."


instrument flight time

Flight time during which the pilot operates an aircraft solely by reference to instruments, under actual or simulated instrument flight conditions. Instrument flight time is not necessarily the total time during which an aircraft operates under instrument flight rules (IFR).


instrument landing system (ILS)

A system of navigation aids and approach lights that provide both horizontal and vertical guidance to aircraft approaching a runway. The ILS is the primary precision approach system in use today around the world. A typical ILS includes a localizer, a glide slope, and outer, middle, and inner marker beacons. The localizer transmits a directional signal that provides left/right guidance. The glide slope is an electronic glide path that defines the proper descent angle to the runway. Marker beacons indicate distance from the runway.


instrument meteorological conditions (IMC)

Weather conditions that require flight under instrument flight rules (IFR). In controlled airspace in the U.S., IMC conditions generally mean that the ceiling is less than 1,000 ft (305 m) and flight visibility is less than three mi (5 km).


instrument rating

A rating added to a pilot certificate that allows a pilot to act as pilot in command of an aircraft solely by reference to flight instruments. An instrument rating is required for operations in clouds or when the ceiling and visibility are less than required for flight under visual flight rules (VFR). A pilot also must hold an instrument rating to act as pilot in command of an aircraft in Class A airspace. In the U.S., Class A airspace begins at 18,000 ft (5,486 m) above mean sea level.


international terminal aerodrome forecast (TAF)

A concise statement of the expected meteorological conditions at an airport during a specified period (usually 24 hours). TAFs use the same codes employed in METAR weather reports. TAFs are scheduled four times daily for 24-hour periods beginning at 0000Z, 0600Z, 1200Z, and 1800Z. They contain the following information: type of report, location, issuance time, valid time, and forecast.


inversion

An increase in temperature with height. An inversion is the reverse of the normal decrease of temperature with height in the troposphere.


isobar

A line of equal or constant barometric pressure as shown on a weather chart.


isotherm

A line of equal or constant temperature as shown on a weather chart.


isogonic line

A line on a chart connecting points of equal magnetic variation.


jet stream

A quasi-horizontal stream of winds of 50 knots or more concentrated within a narrow band. The term usually applies to such winds embedded in the westerlies in the high troposphere.


katabatic wind

A wind blowing downslope.


knots

Nautical miles per hour. Abbreviation: kt, kts, or KTS. One nautical mile (nm or NM) is 6,076 ft (1,852 m). This distance is based on the length of one minute of arc of a great circle—an arc representing the shortest distance between two points on a globe. One knot equals about 1.15 statute miles per hour; therefore 100 knots equals about 115 mph (185 km/h), 150 knots equals about 172 mph (278 km/h), and 200 knots equals about 230 mph (370 km/h). All speeds filed on flight plans and for air traffic control purposes are in knots. In the U.S., light aircraft manufactured in 1976 and later have airspeed indicators marked in knots. Earlier models had airspeed indicators marked in statute miles per hour.

Note that "knots" by definition assumes "per hour." You should never state speed as "knots per hour."


joystick

Name sometimes given to the stick used to control the ailerons and elevators in some aircraft. The joystick is said to have been invented by French aviator Robert Esnault-Pelterie in 1907.

In Flight Simulator, "joystick" means an input device connected to a computer's game port and used to control the ailerons and elevator (and sometimes the rudder as well). A computer joystick may also incorporate buttons and switches to control the throttle, landing gear, flaps, and other functions.


landing gear

The wheels, struts, and other equipment that an aircraft uses to land or maneuver on the ground. Also known as the "undercarriage." The two most common types of landing gear are "taildragger" (sometimes known as “conventional” landing gear) and the "tricycle" arrangements. On a taildragger, the front of the aircraft is supported on two wheels while the tail rests on the ground on a skid or a tail wheel. With a tricycle landing gear, the aircraft sits level on the ground with one nose wheel and two wheels farther back on the aircraft. The main landing gear are those nearest the airplane's center of gravity. Main landing gear almost always come in pairs, and are designed to withstand a greater landing shock than the more fragile nose wheel or tail wheel.


lapse rate

The average decrease of temperature with altitude. In the lower level of the atmosphere, the standard lapse rate is 2 degrees C (3.6 degrees F) per 1,000 feet (305 m). Weather forecasters and pilots use the actual lapse rate to estimate the altitude at which the temperature and dew point will merge and lead to the formation of clouds or precipitation. An increase in temperature with altitude is an inversion.


large aircraft

In the U.S., an aircraft with a maximum certificated takeoff weight of more than 12,500 lbs (5,670 kg). To act as pilot in command of a large aircraft, a pilot must have a type rating for that aircraft.


laser

Acronym for Light Amplification by Stimulated Emission of Radiation. A laser is a device that produces an intense, focused beam of energy in the form of light rays.


lateral axis

One of the three axes of an aircraft, the lateral axis is defined by an imaginary line running from wingtip to wingtip. Movement about the lateral axis is called "pitch" and is controlled by the elevator.


leading-edge slots

Openings near the forward edge of a wing, designed to allow more air to flow over the top of a wing at high angles of attack, delaying the onset of a stall. Leading edge slats and flaps are other so-called high-lift devices.


left-turning tendency

The result of four forces that together cause a propeller-driven aircraft to yaw to the left. This tendency is most pronounced when the airplane is flying at low airspeed and a high angle of attack. The pilot compensates by applying and holding right rudder pressure.

The four forces are: the reactive force, the spiraling slipstream, gyroscopic precession, and "P factor." The reactive force is the opposite and equal force generated by the rotation of the propeller. This force induces a rolling motion about the airplane's longitudinal axis. The spiraling slipstream is the rotating column of air produced by the propeller. It swirls around the fuselage and strikes the left side of the vertical stabilizer, producing a left yaw. Gyroscopic precession occurs when the nose of the airplane rises or falls. This change in pitch attitude applies a force to the spinning mass of the propeller which is 90 degrees ahead of the point where the force was applied. "P factor," or asymmetric propeller loading, induces a left yawing motion because the downward moving propeller blade has a higher angle of attack and produces more thrust than the upward moving blade.


lenticular cloud (lenticularis)

A species of cloud whose elements have the form of more or less isolated, generally smooth lenses or almonds. These clouds appear most often in formations of orographic origin, the result of lee waves, in which case they remain nearly stationary with respect to the terrain (standing cloud), but they also occur in regions without marked orography.


Leonardo da Vinci

1452–1519. Italian artist and scientist, a man of towering intellect and a leader in the transition from the medieval to the modern European consciousness. Da Vinci's scientific interests included anatomy, botany, geology, optics, and mechanics. His designs for human-powered flying machines verged on the fanciful, but his sketches for a hypothetical parachute were scientifically sound.


lift

The upward force produced by an airfoil such as a wing interacting with the air. Lift acts at right angles to the relative wind or the aircraft's flight path. Lift, one of the four fundamental forces in flight, is opposed by weight.


light aircraft

Generally speaking, small single- and twin-engine aircraft. More precisely, in the U.S., aircraft with a maximum certificated takeoff weight of 12,500 lbs (5,760 kg) or less.


light gun signals

Colored lights that control tower operators use to issue instructions to aircraft without radios or aircraft that have a radio failure. The red, green, and white lights convey such messages as "cleared to land," "stop," and "exercise extreme caution." The meaning of all the signals is defined in FAR 91.125.


light icing

Ice, regardless of type, that accumulates slowly. Anti-icing or de-icing equipment prevents accumulations. Light icing may become hazardous to aircraft without anti-icing or de-icing equipment if conditions persist for an hour or more.


lightning

Short, intense electrical discharges generated by thunderstorms. Lightning is rarely a great hazard to most aircraft, but it may damage electronic equipment. Lightning can also temporarily blind a pilot.


light turbulence

In aviation weather reports and pilot reports, turbulence that momentarily causes slight, erratic changes in altitude, attitude, or both. When light turbulence produces rhythmic bumpiness without appreciable changes in altitude or attitude, it is called "chop." In light turbulence, occupants may feel a slight strain against seat belts or shoulder straps. Unsecured objects may be displaced slightly. On large aircraft, food service may be conducted and walking is possible with little or no difficulty.


load factor

The ratio between the total load supported by an aircraft's structure and the actual weight of the aircraft and its contents; also known as "Gs." In steady-state flight, the load factor is 1. When an aircraft turns or pulls up out of a dive, load factor increases. For example, an airplane in a level turn at a bank angle of 60 degrees experiences a load factor of 2. In such a turn, the aircraft's structure must support twice the airplane's weight, and the pilot must increase the aircraft's pitch attitude to produce more lift.


local weather area

In Flight Simulator, a user-defined region with similar weather characteristics. You can create two local weather areas, each with a different type of weather. Unless you specifically create a local weather area, all weather characteristics are assigned to the global weather area.


localizer

The component of the instrument landing system (ILS) that provides left-right guidance to a pilot approaching the runway. The localizer is a highly directional radio signal transmitted on one of 40 channels between 108.10–111.95 MHz. The beam is funnel-shaped. It is typically 10 degrees wide 18 nm from the runway, narrowing to just 700 ft (213 m) wide at the threshold.


Lomcovàk

A tumbling aerobatic maneuver. First conceived of by Ladislav Bezàk, a former world champion aerobatic pilot, the maneuver has at least five variations—all initiated from a near vertical attitude and flown under negative G forces. Although lomcovàk is commonly believed to be the Czech or Polish word for "headache," it apparently comes from a Slovak slang term for a large, stiff drink.


longitudinal axis

An imaginary line running from the nose to the tail of an aircraft; one of the three axes of an aircraft. Rotation about the longitudinal axis is called "roll" and is controlled with the ailerons.


loop

An aerobatic maneuver in which an aircraft flies in a complete vertical circle. An outside loop, begun at the top of the circle, is considerably more difficult to perform, because the pilot encounters negative G-forces throughout the maneuver.


low

An area of low barometric pressure, with its attendant system of winds. Also called a barometric depression or cyclone.


low G condition

In a helicopter, a situation that develops whenever there is less than 1G (the weight of the helicopter) on the rotor disk. The pilot can induce a low G situation by making abrupt cyclic control inputs, flying through turbulence, or when pushing over from a steep climb. In this situation, the nose drops and the aircraft may roll rapidly to the right because the tail rotor is above the main rotor disk and producing thrust to the right. The main rotor may hit the tail boom, and helicopters with semi-rigid rotor systems may experience mast bumping. Either effect may cause loss of the main and tail rotors.

To recover from a low G situation before you lose control, gently apply aft cyclic to raise the nose and add Gs to the rotor disk. Apply left cyclic to counteract the tendency to roll to the right.


Mach 1

The speed of sound. Mach 1 varies according to altitude and temperature: at sea level it is about 762 mph (1,226 km/h); at the bottom of the troposphere, Mach 1 is about 660 mph (1,062 km/h). Above the tropopause, at about 36,000 ft (11,000 m), the speed of sound remains constant.


Mach number

The ratio of an aircraft's speed to the speed of sound. The speed of sound varies with the density of the medium carrying the sound waves. For example, sound travels faster through iron or water than through air. Because the density of air decreases with altitude, the speed of sound also decreases. Sound travels at approximately 1,226 km/h (762 mph) at sea level, 1,138 km/h (707 mph) at 20,000 ft (6096 m), and 664 mph (1,068 km/h) at 35,000 ft (10,668 m). Named for Ernst Mach, Austrian physicist.


magnetic compass

A device for determining direction relative to the earth's magnetic field.


magnetic course

A line drawn on a chart between two points with its direction referenced to the earth's magnetic north pole.


magnetic heading

The direction in which an aircraft is pointed, measured relative to the magnetic north pole. The magnetic heading is displayed on the compass. A pilot determines the magnetic heading to fly by compensating for the difference between true north and magnetic north and then adjusting the resulting magnetic course to compensate for wind. If the wind is blowing directly along the intended course, the magnetic heading equals the magnetic course. If a crosswind component is present, however, a pilot must turn the aircraft slightly into the wind to compensate. Under these conditions, the airplane's track over the ground is slightly different from the direction in which the nose is pointing.


magnetic variation

The angle between "true north" and "magnetic north"; that is, the angle between the geographic north pole and the magnetic north pole as measured from a point on the earth. To determine the magnetic course between two points on the earth's surface, a pilot must determine the true course—the angle formed between the line drawn on a chart and lines of longitude—and then add or subtract the variation at points along that course.


magneto

A device that creates an electric current by rotating a magnet. In aircraft engines, the crankshaft turns the magnetos, which provide the electrical energy to fire the spark plugs. This arrangement ensures that the spark plugs fire even if the aircraft's battery and electrical system fail. Certificated aircraft engines typically have two sets of magnetos for additional redundancy.


maneuvering speed
maneuvering speed (Va)

The maximum speed at which the pilot can use full, abrupt control movement without creating excessive G forces that could damage the aircraft; the maximum speed at which you can safely stall an aircraft. Pilots also use maneuvering speed when flying through turbulent air.

Abbreviated Va, maneuvering speed is not marked on the airspeed indicator.


manifold pressure gauge

An instrument that measures the air pressure in the intake manifold of a piston engine. Usually calibrated in inches of mercury, this instrument (really a barometer) is used in combination with the tachometer to set engine power. Most small training aircraft have only a tachometer. Aircraft with larger engines and aircraft with constant-speed propellers usually have manifold pressure gauges.


marker beacons

Low-power radio beacons that identify specific positions along an instrument approach, usually an ILS. A typical ILS has at least two marker beacons. The outer marker (OM) normally indicates the point at which an aircraft intercepts the electronic glide slope. It transmits three dashes in Morse Code. On the instrument panel, the OM is indicated by a blue light. The middle marker (MM) indicates a position about 3,500 ft (1,067 m) from the runway threshold. It also marks the point where an aircraft is about 200 ft (61 m) above the elevation of the runway touchdown zone. The middle marker transmits a "dot-dash-dot-dash" code and is indicated in the cockpit by an amber light.

Some ILS's also have an inner marker (IM), which indicates the point at which an airplane flying along the proper glideslope reaches the decision height. The inner marker transmits a rapid "dot-dot-dot-dot" code and is indicated in the cockpit by a white light.


Max Immelmann

1890–1916. One of Germany's first great fighter pilots, credited (probably erroneously) as the inventor of the "Immelmann" maneuver. Nicknamed "the Eagle of Lille," Immelmann learned the basics of air combat from Oswald Boelcke, with whom he often flew missions. Among the numerous decorations Immelmann earned before being killed in action was the coveted Blue Max.


MDA (minimum descent altitude)

The lowest altitude to which descent is authorized on final approach or during circle-to-land maneuvering during a non-precision instrument approach. You can descend from the MDA only when you are in a position to complete a normal approach and landing by visual reference to the runway environment.


mean sea level (MSL)

The average level of the earth's oceans; used as reference for true altitude—the vertical distance of an aircraft above sea level. Airport, terrain, and obstacle elevations shown on aeronautical charts are expressed as true altitude.


measured ceiling

A ceiling classification applied when the ceiling value has been determined by instruments or the known heights of unobscured portions of objects other than natural landmarks.


medical certificate

In the U.S., a certificate showing that a pilot, required flight crewmember, or air traffic controller meets a set of physical and mental standards established for the safe operation of an aircraft or the performance of other duties. The FAA issues third, second, and first class medical certificates. The certification standards are more restrictive with each class. Student, recreational, and private pilots are required to hold at least a third class medical certificate, which is valid for 24 or 36 months. A second class medical is required for certain commercial operations. It is valid for 12 months for those operations and for 24 months for non-commercial operations. Airline pilots require a first class medical, which is valid for 6 months for air carrier operations, 24 months for certain commercial operations, and 24 months for non-commercial operations.


METAR

Abbreviation for Aviation Routine Weather Report, the standard report for hourly weather observations taken at airports. The U.S. recently adopted the METAR to replace SA reports. A METAR includes the following information: type of report; station designator; time of report; wind; visibility; weather and obstructions to visibility; sky condition; temperature and dew point; altimeter setting; and remarks.


microburst

Violent localized winds often associated with thunderstorms. In a microburst, strong vertical downdrafts spill out of a thunderstorm and then spread along the ground, like water poured from a bucket. These downdrafts can exceed 6,000 feet per minute (1,829 m/sec) and create strong wind shears—areas where the speed and direction of the wind change abruptly. An airplane flying through a microburst and its associated wind shear experiences rapid changes in airspeed and can sink to the ground if caught in a strong downdraft.


millibar (mb)

An internationally used unit of pressure equal to 1,000 dynes per square centimeter. It is convenient for reporting atmospheric pressure.


mixed ice

A combination of clear and rime ice. Mixed ice forms when water drops vary in size or when liquid drops are intermingled with snow or ice particles. It can form rapidly. Ice particles become imbedded in clear ice, building a rough accumulation sometimes in a mushroom shape on the leading edges of an aircraft's surfaces.


mixture control

A device for controlling the ratio between fuel and air entering an engine's carburetor or fuel injection system. In most aircraft, the mixture control is a push-pull knob or lever marked in red usually located to the right of the throttle.

Because aircraft engines operate over a wide range of altitudes, the pilot must adjust the mixture to produce the most efficient fuel/air mixture as an airplane climbs into less dense air or descends into more dense air. A mixture that is too rich contains too much fuel for the existing conditions and causes the engine to run rough and lose power. A mixture that is too lean can cause an engine to overheat or cause detonation, the sudden, explosive combustion of fuel within the cylinders.


moderate icing

Ice, regardless of type, that accumulates at a rate that requires the use of anti-icing or de-icing equipment. Aircraft without such equipment must divert immediately.


moderate turbulence

In aviation weather reports and pilot reports, turbulence that causes changes in altitude or attitude and small variations in airspeed. The aircraft remains in positive control at all times, Occupants feel definite strains against seat belts or shoulder straps. Unsecured objects are dislodged. On large aircraft, food service and walking are difficult.


mmo

Abbreviation for Mach maximum operating speed; the maximum airspeed, indicated in Mach number, at which an aircraft can be operated safely. The actual value of mmo varies with atmospheric pressure, temperature, and other factors.


mountain waves

A standing wave or lee wave to the lee of a mountain barrier. Waves created by massive amounts of air pushed over mountain ranges such as the Rockies and the Sierra Nevada in the U.S. Intense mountain waves are typically produced when a strong, turbulent jet stream flows directly across a mountain ridge. Sailplane pilots often use mountain waves to soar to high altitudes—50,000 ft (15,240 m) or more.


NASA

Abbreviation for National Aeronautics and Space Administration, a civilian agency of the U.S. government created in 1958 with the responsibility for all nonmilitary developments in aeronautics and space flight. NASA replaced the National Advisory Committee for Aeronautics.


National Transportation Safety Board (NTSB)

In the U.S. the government agency that investigates aircraft accidents and determines their probable cause. The NTSB is independent of the FAA, which regulates aviation. The FAA participates in accident investigations and responds to recommendations made by the NTSB when the board determines that new regulations, procedures, or equipment would help prevent future accidents.


nautical mile (nm)

A distance of about 6,076 ft (1852 m). The nautical mile is based on the length of one minute of arc of a great circle. In aviation, distances and speeds are measured in nautical miles (nm) and nautical miles per hour (knots).


NAV

Abbreviation for navigational; usually refers to a navigational radio, as in "NAV 1" or "NAV 2."


Nav
NAV/COM

A radio that combines the functions of communication and navigational radios.


navigation lights

The basic anti-collision light system required on all aircraft certified to fly at night. The system includes a red light on the left wingtip, a green light on the right wingtip, and a white light on the tail. These lights tell other aircraft which direction an aircraft is flying when only the lights can be seen. Navigation lights must be turned on between sunset and sunrise.


nimbostratus

A principal cloud type, gray colored, often dark. Its diffuse appearance is caused by more or less continuously falling rain or snow, which in most cases reaches the ground. A nimbostratus cloud is thick enough throughout to blot out the sun.


Ninety-Nines
Ninety-Nines (99s)

Association of women fliers formed in 1929 with 99 charter members, including Amelia Earhart, Jackie Cochran, Louise Thaden, and Amy Johnson. The Ninety-Nines were responsible for the acceptance and respect accorded women contestants in the air races of the 1930s. Today the Ninety-Nines is a worldwide organization with thousands of members.


nondirectional radio beacon (NDB)

A radio beacon that transmits nondirectional signals in the low or medium frequency band (190–535 kHz); today used primarily for NDB nonprecision approaches and in conjunction with the outer marker component of an ILS. An automatic direction finder (ADF) points to these beacons.


nose over

To rapidly lower the nose relative to the horizon; decrease pitch. On the ground, a nose over—an aircraft tipping forward or doing a somersault, can result when the nose wheel digs into a soft surface or when a tailwheel-equipped airplane decelerates too rapidly.


obscuration

In weather reports, denotes a sky hidden by surface-based phenomena and vertical visibility restricted overhead.


occluded front
occluded front (occlusion)

A composite of two fronts as a cold front overtakes a warm front or a quasi-stationary front.


oleo-pneumatic

A hydraulic-air system usually incorporated into aircraft landing-gear systems. Oleo-pneumatic shock absorbers dissipate the shock of landing by forcing fluid through a restrictor valve from the upper chamber of the strut to the lower chamber.


omni-bearing indicator (OBI)

The instrument that displays information about an aircraft's position relative to a VOR station. The OBI includes a needle, or course deviation indicator (CDI) to show the aircraft's position relative to a selected course or "radial," and a TO-FROM-OFF indicator that shows the aircraft's position relative to the VOR station. A glide-slope needle is also included in some OBI. Each OBI is typically connected to a navigation receiver (NAV 1 or NAV 2).


ornithopters
ornithopter

Hypothetical human-powered flying machine based on flapping wings. Leonardo da Vinci was perhaps the first to attempt a scientific design of ornithopters, but the idea reaches back at least to the Greek legend of Daedalus and Icarus. No actually working ornithopter has ever been built.


orographic

Of, pertaining to, or caused by mountains as in orographic clouds, orographic lift, or orographic precipitation.


Otto Lilienthal

1848–1896. German aeronautical engineer and hang glider pilot whose experiments with stability, lift, and control were highly influential to such later aviators as the Wright brothers. Lilienthal applied his studies of bird flight and aerodynamic theory to the design, construction, and experimental flight of 18 gliders. The first man to be photographed in a glider, Lilienthal was killed when one of his craft crashed in 1896.


ozone

An unstable form of oxygen. The heaviest concentrations of ozone are in the stratosphere. Ozone is corrosive to some metals and it absorbs most ultraviolet solar radiation.


PAPI (precision approach path indicator)

A system of lights to help pilots determine if they’re on the proper descent path to a runway. A PAPI system is similar to a VASI, but it uses one row of four lights. If you are on the proper glide path (usually 3 degrees), you see two white lights on the left side of the PAPI light bar and two red lights on the right side. If you are slightly above the proper glide path, you see three white lights on the left and one red light on the right. If you are well above the proper glide path, you see four white lights. If you are slightly below the proper glide path, you see one white light on the left and three red lights to the right. If you are well below the proper glide path, you see four red lights.


parasite drag

Resistance to motion through the air composed of form drag (due to landing gear, radio antennas, shape of the wings, and so on), skin friction, and airflow interference between aircraft components (such as the junction of the wings and fuselage, or fuselage and tail). Parasite drag increases as the square of velocity. It is one component of total drag, the force that opposes thrust. The other component is induced drag, a byproduct of lift.


partial obscuration

A designation of sky cover when part of the sky is hidden by surface-based obscuring phenomena.


Patty Wagstaff

1951– . American aerobatic pilot. Wagstaff was the 1993 International Aerobatic Club Champion and a three-time U.S. National Aerobatic Champion. A member of the U.S. Aerobatic Team, she is also an aerobatics coach, an aerial competition judge, and a movie stunt pilot.


Paul Poberezny

American fighter pilot and flight instructor in WWII and Korea, and founder and chairman of the Experimental Aircraft Association. Poberezny organized the EAA and its first fly-in in 1953, from which he became a leading figure in representing the interests of sport-flying enthusiasts and amateur aircraft builders worldwide. Involved in aviation for most of his life, Poberezny has designed more than 15 airplanes and has served as editor for a number of aviation publications. His son, Tom, is the current president of the EAA.


Percy Pilcher

1866–1899. Scottish marine engineer whose experiments with gliders between 1895 and 1899 produced a number of design advances. Pilcher was developing a light engine for use with one of his gliders but did not complete the project. Like his mentor, Otto Lilienthal, Pilcher died when one of his gliders crashed.


performance booster

Software to enhance performance of CD-ROM versions of Flight Simulator or scenery add-ons. The performance booster monitors your aircraft's position and automatically loads scenery from the CD-ROM drive to a disk cache on your hard drive.


phonetic alphabet

A spoken alphabet endorsed by the International Civil Aviation Organization (ICAO) and used by pilots and air traffic controllers to avoid confusion during radio communications. Instead of saying "a," "b," "c," pilots say "alpha," "bravo," "charlie," and so on.


pilot certificate

In the U.S., a pilot license. The FAA issues several types of pilot certificates, including student, recreational, private, commercial, certified flight instructor, and airline transport pilot certificates. Pilot certificates define broad privileges and limitations. Ratings on those certificates (single-engine land, instrument, multi-engine land, helicopter, and so on) further specify the classes of aircraft that a pilot may fly and whether the pilot is allowed to act as pilot in command when the weather does not meet the minimums specified for flight under visual flight rules (VFR).


pilot in command
pilot in command (PIC)

The pilot responsible for the operation and safety of an aircraft during flight time. For purposes of logging flight time, a pilot holding a recreational, private, or commercial pilot certificate may log as pilot-in-command time only that flight time during which that pilot is the sole manipulator of the controls. The pilot must hold an appropriate pilot certificate and rating for the aircraft. An airline transport pilot may log as PIC time all of the flight time during which that pilot acts as PIC. A certified flight instructor may log as PIC time all flight during which that pilot acts as PIC.


pilotage

Flying cross-country, from one visible landmark to another, using only a chart.


PIREP

Abbreviation for "pilot report." A PIREP describes actual inflight conditions, such as the height of clouds, visibility, precipitation, turbulence, and icing. On weather reports in the U.S., pilot reports are preceded by the letters "UA." A pilot report includes the following items: position relative to a weather reporting station or navigation aid, time (UTC), altitude, aircraft type, cloud types and altitudes, visibility, outside air temperature, wind, turbulence, and remarks. Some of the information may be omitted.


pitch

Movement of an aircraft about its lateral axis (nose up or nose down), or the angle of an airplane's nose above or below the horizon. The pilot moves the control stick or yoke forward and back to move the elevator, located on the horizontal stabilizer. Forward pressure lowers the nose; back pressure raises the nose.


pitot static system
pitot-static system

The sensors, connecting lines, and flight instruments that measure, transmit, and display information about an aircraft's airspeed, altitude, and rate of climb or descent. The pitot-static system includes the pitot tube, static ports, and tubing that connects the sensors and instruments in the cockpit. The airspeed indicator is connected to both the pitot tube and the static ports. The altimeter and vertical speed indicator are connected only to the static ports.


pitot tube

A small metal probe, usually attached to a wing or the nose of an aircraft, that measures ram air pressure as the aircraft moves. The pitot tube is part of the pitot-static system. It is connected directly to the airspeed indicator, which displays the ram air pressure on a scale, usually calibrated in knots. The pitot tube usually has a heater to prevent ice from blocking the device. The probe is named after Henri Pitot (1695–1771), a French scientist who invented devices to measure the flow of water in rivers and canals.


practical test

In the U.S., an oral and flight test required for a pilot certificate or rating. Practical tests are given by government inspectors or designated examiners. The required knowledge and performance standards for each pilot certificate or rating are specified in a series of Practical Test Standards (PTS) available from the Government Printing Office or from many publishers of aviation-related books and study guides.


precipitation

Any or all forms of water particles, whether liquid or solid, that fall from the atmosphere and reach the surface. Precipitation is distinguished from cloud and virga in that it must reach the surface.


precipitation-induced fog

Fog formed when relatively warm rain or drizzle falls through cool air. Evaporation from the precipitation saturates the cool air and forms fog. Precipitation-induced fog can become quite dense and persistent. It often extends over large areas, completely suspending flight operations. It is most commonly associated with warm fronts, but it can occur with slow-moving cold fronts and with stationary fronts. Precipitation-induced fog is especially critical because it occurs in precipitation and related hazards such as icing, turbulence, and thunderstorms.


pressure altimeter

An aneroid barometer with a scale graduated in altitude instead of pressure. Using standard atmospheric pressure-height relationships, a pressure altimeter shows indicated altitude (not necessarily true altitude). It may be set to measure indicated altitude from any arbitrarily chosen level.


pressure altitude

The altitude indicated when the altimeter is set to 29.92 inches of mercury or 1013.2 millibars. Pressure altitude is used in several important calculations, including the determination of density altitude, true altitude, and true airspeed. In the U.S., aircraft operating at 18,000 ft (5486 m) or higher fly at "flight levels," which are pressure altitudes. When operating at or above FL 180, the pilot should set the altimeter to 29.92 to display pressure altitude.


prevailing easterlies

The broad current or pattern of persistent easterly winds in the tropics and polar regions.


prevailing visibility

In the U.S., the greatest horizontal visibility that is equaled or exceeded throughout half of the horizon circle; it need not be a continuous half.


prevailing westerlies

The dominant west-to-east motion of the atmosphere, centered over middle latitudes of both hemispheres.


primary flight instruments

The six instruments displayed on the standard instrument cluster: airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator.


private pilot certificate

In the U.S., a pilot certificate issued to a person who does not intend to act as a pilot in command for compensation or hire. To be eligible for a private pilot certificate, a person must be at least 17 years old and hold a current third class medical certificate. To earn a private pilot certificate, a person must acquire at least 40 hours of flight time, including 20 hours of flight instruction and 20 hours of solo flight time. The training must include basic maneuvers, cross-country navigation, and other specific tasks.


prognostic chart
prognostic chart (PROG)

A chart of expected or forecast weather conditions.


radar

Acronym for RAdio Direction And Ranging, a device for detecting distant objects by reflecting radio waves from their surfaces. The British first integrated radar into their military defenses, and its value during the Battle of Britain was enormous. Today radar is the primary tool for air traffic control. Some aircraft also carry weather radar, designed to detect precipitation and wind shears associated with thunderstorms and other hazards.


radar altitude

The altitude of an aircraft determined by radar or radio altimeter. It is the actual distance between an aircraft and the ground or water surface directly beneath it.


radial

One of the 360 "spokes," one for each degree in a circle, radiated from a VOR station. To fly a specific course, the pilot tunes the appropriate VOR station and selects a radial to fly. An indicator in the cockpit, called an OBI, shows the aircraft's position relative to that radial.


radial engine

A type of reciprocating piston engine in which the cylinders are arranged like the spokes of a wheel.


radarsonde observation

An observation in which winds are determined by tracking a balloon-borne target with radar.


radiation fog

Fog characteristically formed over land at night or near daybreak when cooling of the earth's surface lowers the air temperature near the ground to or below the initial dew point. Radiation fog is especially common on calm, clear nights. It is relatively shallow and may be dense enough to hide the entire sky.


radio stack

The area where the COM, NAV and transponder radios are installed in an aircraft instrument panel. Radios are usually arranged in a vertical column, or stack.


radiosonde

A balloon-borne instrument for measuring pressure, temperature, and humidity aloft.


rate of climb

The speed (usually measured in feet per minute) at which an aircraft is climbing. The term sometimes is stretched to include the rate of descent. The rate of climb is read on the vertical speed indicator (VSI).


rating

In the U.S., an endorsement added to a pilot certificate that specifies the classes of aircraft (single-engine land, instrument, multi-engine land, helicopter, and so forth) that a pilot may fly and whether the pilot is allowed to act as pilot in command when the weather does not meet the minimums specified for flight under visual flight rules (VFR).


rawinsonde observation

A combined winds aloft and radiosonde observation. Winds are determined by tracking the radiosonde by radio direction finder or radar.


recreational pilot certificate

In the U.S., a pilot certificate issued to a person who intends to fly only for recreation in basic aircraft. To be eligible for a recreational pilot certificate, a person must be at least 17 years old and hold a current third class medical certificate. To earn a recreational pilot certificate, a person must acquire at least 30 hours of flight time, including 15 hours of flight instruction. Recreational pilots are subject to many restrictions. For example, they may not carry more than one passenger and must remain within 50 nm of an airport where they received flight instruction. Recreational pilots are restricted to basic single-engine aircraft with no more than 180 hp, four seats, and fixed landing gear. They also cannot fly at night, above 10,000 ft (3000 m), or when the visibility is less than 3 sm.


relative humidity

The ratio, usually expressed in percent, between the amount of water present in the air and the maximum amount that could be present at a given temperature. Warm air can hold more water vapor than cool air. If temperature increases and the amount of water vapor in the air remains constant, relative humidity decreases. If temperature drops while the amount of water vapor stays constant, relative humidity increases. Air with 100 percent relative humidity is saturated. The temperature at which the air reaches 100 percent relative humidity is called the dew point.


relative wind

The speed and direction of air striking an airfoil; that is, the air flow caused by an aircraft or airfoil's movement through the air. The relative wind blows parallel and opposite to the airfoil. The angle between the relative wind and the chord line is the angle of attack. Lift acts perpendicular to the relative wind.


retreating blade stall

In a helicopter, a condition in which the rotor blades on the left side of the rotor disk (when seen from above) exceed their critical angle of attack and stall. This situation can occur when a helicopter is flying at a high forward speed, which increases the angle of attack of the rotor blades moving toward the rear of the aircraft. This phenomenon is the primary limitation on a helicopter’s maximum speed. Turbulence, low rotor RPM, steep and abrupt turns, high gross weight, and high density altitude can also induce retreating blade stall.

The signs of retreating blade stall include a low-frequency vibration, a tendency for the helicopter’s nose to pitch up, and a roll to the left.

To recover from a retreating blade stall, lower the collective to reduce the rotor’s angle of attack and slow down.


Richard Whitcomb

1921– . American engineer. At the laboratory of the National Advisory Committee for Aeronautics (NACA), Whitcomb developed the "area rule" for reducing drag at transonic speeds by pinching in the fuselage where it meets the wing. In 1955 he won aviation's prestigious Collier Trophy for inventing this "Coke-bottle effect" during his breakthrough redesign of the Convair YF-102's fuselage.


ridge

In meteorology, an elongated area of relatively high atmospheric pressure; usually associated with and most clearly identified as an area of maximum anticyclonic curvature of the wind flow.


ridge lift

An area of rising air created when wind blows against the side of a ridge and is deflected upward. In such conditions, sailplanes can stay aloft for hours by flying parallel to a ridge, riding those rising currents of air.


rigid rotor system

One of three main types of rotor system used in modern helicopters. A rigid rotor system has three or more main rotor blades. The blades flap—move up and down—independently to compensate for dissymmetry of lift. They also feather—twist at the rotor hub—independently to adjust angle of attack as they rotate. Unlike a fully articulated system, a rigid rotor system is hingeless and the rotors and can lead and lag independently.

Rigid rotor systems are the most expensive types of rotors to manufacture. They are typically made of composite materials and titanium and tend to give a relatively rough ride. However, they resist low-G conditions and ground resonance and require less maintenance than other rotor systems.


rime ice

White or milky and opaque granular deposits of ice formed by the rapid freezing of supercooled water droplets on exposed parts of an aircraft. Rime ice forms when drops are small, usually in stratiform clouds or light drizzle. The liquid portion remaining after initial impact freezes before the drop spreads over the aircraft surface. The small frozen droplets trap air between them giving the ice a milky appearance. Rime ice is lighter than clear ice, but its irregular shape and rough surface quickly degrade the efficiency of airfoils.


roll

Rotation about an aircraft's longitudinal axis. The pilot controls roll, or the bank of the wings, with the ailerons. A roll is also an aerobatic maneuver in which an airplane rotates completely around its longitudinal axis.


roll cloud

A dense and horizontal roll-shaped accessory cloud located on the lower leading edge of a cumulonimbus. Roll clouds can also be found near a rapidly developing cumulus cloud. They indicate turbulence.


rotary engine

Type of piston engine, common in WWI aircraft, with a stationary crankshaft and cylinders that rotate around the crankshaft. Rotary engines were lighter-weight, more reliable, and more easily cooled than many contemporary radial and inline piston engines, but they had high fuel consumption and their rotational inertia sometimes made an aircraft difficult to maneuver.


rotation

Pulling back on the control yoke or stick to raise the nose of an aircraft during the takeoff roll.


rotation speed (Vr)

The speed at which the pilot should pull back on the control yoke or stick to begin raising an aircraft's nose during takeoff.


rotor cloud

A turbulent cloud formation found in the lee of some large mountain barriers, the air in the cloud rotates around an axis parallel to the range; indicative of possible violent turbulence.


rudder

A movable control surface usually mounted on the vertical stabilizer of the tail. The rudder moves the aircraft about its vertical, or yaw axis. It does not, however, turn the airplane. It is used primarily to balance forces in turns and to counteract yawing motions induced by the propeller during flight. A pilot moves the rudder by applying pressure to the left or right rudder pedal. The pedals are mounted on the floor of the cockpit. In normal maneuvering, the pilot uses simultaneous aileron and rudder pressures to maintain balanced or coordinated flight.


runway visual range (RVR)

The horizontal distance (in feet or meters) that a pilot should be able to see down the runway from the approach end. RVR is based on either the sighting of high intensity runway lights or on the visual contrast of other objects, whichever yields the greatest visual range.


sailplane

A highly efficient unpowered aircraft that, unlike a glider, can maintain or gain altitude by riding thermals or other rising air.


saturated adiabatic lapse rate

The rate of decrease of temperature with height as saturated air is lifted with no gain or loss of heat from outside sources. This value varies with temperature, and is greatest at low temperatures.


scud

Small detached masses of stratus fractus clouds below a layer of higher clouds, usually nimbostratus. More generally, "scud" is any low-level clouds or fog. Pilots who fly at low altitude beneath clouds are said to be "scud running."


sea fog

A type of advection fog formed when air that has been lying over a warm surface is transported over a colder water surface.


semimonocoque

A kind of fuselage construction that distributes the structural load of the aircraft between its skin and the framework.


semi-rigid rotor system

One of three main types of rotor system used in modern helicopters. A semi-rigid rotor system has two main rotor blades. The blades flap—move up and down—as a unit, like a teeter-totter, to compensate for dissymmetry of lift. They also feather—twist at the rotor hub—as a unit to adjust angle of attack as they rotate. The rotor system is also underslung to compensate for the Coriolis effect—the leading and lagging of the main rotor blades as the center of mass moves toward and away from the rotor’s axis of rotation.

Semi-rigid rotor systems are relatively inexpensive to maintain, but their flapping characteristics can lead to mast bumping. They are also susceptible to low-G conditions.


settling with power

The tendency of a helicopter to descend rapidly into its own rotor downwash. The high descent rate associated with settling with power is the most common cause of helicopter accidents. Settling with power occurs when the helicopter has an airspeed of less than 10 knots, is in a descent of more than 300 fpm, and is developing more than 20 percent power.

Most often you encounter these conditions while hovering out of ground effect without maintaining altitude, when attempting to hover above the helicopter’s out-of-ground-effect hover ceiling, or during a landing with a tailwind, which blows the downwash beneath the helicopter.

This phenomenon is caused by vortices that form at the root of the rotor blades and then travel outward. Like a stalled airplane wing, the rotors no longer produce enough lift to maintain the helicopter in level flight or a gradual descent. Settling with power is usually associated with a low-frequency vibration, loss of cyclic control effectiveness, and a rapid descent rate.

To recover, you must move the helicopter out of its downwash by traveling forward, backward, or to the side at an airspeed of at least 10 knots.


severe icing

Icing, regardless of type, that accumulates so rapidly that even aircraft equipped with anti-icing or de-icing equipment must divert immediately.


severe turbulence

In aviation weather reports and pilot reports, turbulence that causes large, abrupt changes in altitude, attitude, or both. Severe turbulence usually causes wide variations in indicated airspeed. The aircraft may be momentarily out of control. Occupants are forced violently against seat belts or shoulder straps. Unsecured objects are tossed about. On a large aircraft, food service and walking are impossible.


shock wave

Created when airflow changes abruptly from subsonic to supersonic speed, causing an enormous increase in air pressure and temperature. When an aircraft travels above Mach 1, shock waves bend backward to form a cone. If this cone reaches the earth's surface, it causes an explosive sound called a sonic boom.


shower

Precipitation from a cumuliform cloud. A shower is characterized by the suddenness with which it begins and ends, by a rapid change of intensity, and usually by rapid change in the appearance of the sky. Showery precipitation may be in the form of rain, ice pellets, or snow.


sink rate

Negative vertical velocity, usually expressed in feet per second.


skid

A turn in which the rate of turn is too great for the angle of the bank. In a skid, the ball at the bottom of the turn coordinator moves to the outside of the turn. To correct a skid, use the ailerons to increase the bank, reduce rudder pressure, or both, in the direction of the turn.


slat

A movable auxiliary airfoil on the leading edge of a wing. The slat extends into the flow of air and creates a gap that allows air to flow smoothly over the top of the wing, delaying the stall at high angles of attack.


slewing

In Flight Simulator, a method of rapidly changing aircraft position, direction, location, or altitude without flying.


slip

A turn in which the rate of turn is too slow for the angle of the bank. In a slip, the ball at the bottom of the turn coordinator moves to the inside of the turn. To correct for a slip, use the ailerons to decrease the bank, increase rudder pressure, or both in the direction of the turn. Pilots also use forward slips and side slips to correct for crosswinds during landings and to increase an aircraft's rate of descent without increasing its airspeed.


spin

A steep, spiraling descent during which an aircraft is stalled and rotating rapidly. The characteristic rotation is the result of a strong yawing moment that occurs when one wing is stalled while the other still produces some lift.


spoilers
spoilers (speed brakes)

Panels on an aircraft's wings that disrupt the flow of air over the wing surface. Spoilers (sometimes called “speed brakes”) reduce the wing's lift and increase drag. Spoilers enable a jet aircraft to make a rapid descents without building excess speed. They are also used immediately after landing to "dump" lift and increase braking efficiency. Sailplane pilots also use spoilers during descent and landing to control their rate of descent.


spool up

To increase power in a jet engine.


squall

A sudden increase in wind speed by at least 15 knots to a peak of 20 knots or more and lasting for at least one minute. The essential difference between a gust and a squall is the duration of the peak speed.


squall line

A narrow band of active, often severe, thunderstorms not associated with a front. Squall lines often form ahead of a cold front in moist, unstable air, but they can also develop in unstable air far removed from any front. Squall lines present the single most intense weather hazard to aircraft. They usually develop rapidly and reach maximum intensity during the late afternoon and early evening. Squall lines may also be too long to fly around and too wide and severe to fly through, creating a true barrier in the sky.


stability
stability (aircraft)

Generally, a measure of how an object reacts after it is disturbed by an outside force. Aircraft stability is classified as three types. Positive stability is the tendency to return to steady state flight after a change in attitude or power. Aircraft are generally designed to exhibit positive stability. An aircraft with neutral stability would remain in the new attitude after being disturbed and not return to its initial condition. An aircraft with negative stability would diverge from its initial condition, with the oscillations increasing with time.

Stability can also be classified as "static" and "dynamic." Static stability is the initial tendency to return to equilibrium. Dynamic stability refers to dampening of oscillations over time.


stability (atmospheric)

A measure of the vertical movement of air within an air mass. More specifically, it is a state of the atmosphere in which the vertical distribution of temperature is such that a parcel of air resists displacement from its initial level.


stall

A sudden loss of lift caused by a disruption of the normal smooth flow of air over the upper surface of a wing. A stall is an aerodynamic phenomenon and has nothing to do with the engine. A stall occurs when a wing's angle of attack reaches a specific value, called the critical angle of attack. It is this angle between the wing and the oncoming air—not the airplane's speed, weight, or pitch attitude relative to the horizon—that determines when a wing stalls. In fact, an airplane can stall at any airspeed and in any attitude.


stall speed

The speed at which an aircraft enters a stall under a specified set of conditions. Although an airplane always stalls when the wing's angle of attack reaches the critical angle of attack, the speed at which the stall occurs depends on the aircraft's weight, load factor, the amount of thrust being produced, angle of bank, position of flaps and landing gear, and other factors.

In fact, an airplane can stall at any airspeed—because regardless of speed, a stall occurs only when the angle between the relative wind (parallel and opposite to the aircraft's flight path) and the wing reaches the critical angle of attack.


standard atmosphere

A hypothetical atmosphere based on climatological averages. The most important constants defined in the standard atmosphere are: a surface temperature of 15 degrees C (59 degrees F) and a surface pressure of 1,013.2 millibars (29.92 in of mercury) at sea level; a lapse rate in the troposphere of approximately 2 degrees C (3.6 degrees F) per 1,000 ft (6.5 degrees C per km), a drop in pressure of approximately 1 in of mercury per 1,000 ft (110 mb per 1,000 m), a tropopause of approximately 36,000 ft (11 km) with a temperature of –56.5 degrees C; and an isothermal lapse rate in the stratosphere to an altitude of approximately 80,000 ft (24 km).


standard conditions

An arbitrary standard established as a baseline for calculations used in meteorology, aviation, and aerodynamics. A set of standard conditions exists for each altitude. At sea level, standard conditions are defined as 29.92 inches of mercury (1,013 millibars) and 59 degrees F (15 degrees C).


standard pressure

An arbitrary standard established as a baseline for calculations used in meteorology, aviation, and aerodynamics. A standard pressure is defined at all altitudes. At sea level, the standard is 29.92 in of mercury or 1,013 millibars.


standard rate turn

A turn of either 3 degrees or 1.5 degrees per second. Small aircraft typically use the 3 degrees/second rate, which results in a 360-degree turn after 2 minutes. Large, fast aircraft typically use the slower rate, which results in a 360-degree turn in 4 minutes. Pilots use the standard rate turn while flying under Instrument Flight Rules (IFR). It provides a steady, predictable, and easy-to-control rate of turn. Standard rate turns are also useful if the heading indicator fails. The pilot can make accurate turns to specific headings by banking at the standard rate and timing the turn.


standard temperature

An arbitrary standard used by aeronautical engineers and pilots in calculations to determine aircraft performance, true airspeed, true altitude, and so forth. The standard temperature is part of the definition of the International Standard Atmosphere (ISA). At sea level, the standard temperature is defined as 59 degrees F (15 degrees C). The standard temperature of dry air drops by about 3.5 degrees F (2 degrees C) per 1,000 ft (305 m). The standard temperature drops to about 32 degrees F (0 degrees C) at about 7,500 ft (2,300 m).


standardized instrument cluster

An industry-accepted standard for arranging the six most commonly used flight instruments on an aircraft instrument panel. The instruments are arranged in two rows. The top row contains the airspeed indicator, attitude indicator, and altimeter. The bottom row contains the turn coordinator, heading indicator, and vertical speed indicator.


stationary front

A front in which neither air mass is replacing the other. In such cases, the surface winds tend to blow parallel to the frontal zone. The slope of a stationary front is normally shallow, although it may be steep depending on wind distribution and density difference.


statute mile (sm)

A distance of 5,280 ft (1,609 m). In the U.S., statute miles are used to measure visibility in weather reports. Speeds and distances are measured and reported in nautical miles (6,076 ft or 1,852 m) or nautical miles per hour (knots).


steady state flight
steady-state flight

Flight in which the opposing pairs of forces (lift and weight, thrust and drag) are balanced. An aircraft is in steady-state flight when it flies at a constant altitude and airspeed or when it flies at a constant airspeed and is climbing or descending at constant rate.


STOL

Abbreviation for "short takeoff and landing." It describes aircraft capable of operating from airfields with short runways.


steam fog

Fog formed when air blows from a cold surface (either land or water) over warmer water.


stratiform

Clouds with extensive horizontal development. Stratiform clouds develop in stable air and, therefore, are composed of small water droplets.


stratocumulus

A low, predominantly stratiform cloud. It is usually a mosaic of gray and whitish patches or layers. The layers may or may not merge, and such clouds are rounded or roll-shaped with relatively flat tops.


stratosphere

The region of the earth's atmosphere above the troposphere and tropopause, beginning at an altitude of 5–10 mi (8–16 km), depending on latitude and season. The stratosphere is a region of relatively uniform temperatures and winds, extending to about 30 mi (48 km), where it meets the mesosphere.


stratus cloud
stratus clouds

A low, gray cloud layer or sheet with a fairly uniform base, formed in stable air. Stratus clouds sometimes appear in ragged patches. They seldom produce precipitation but may produce drizzle or snow grains.


student pilot certificate

In the U.S., a pilot certificate issued to a pilot in training. To be eligible for a student pilot certificate for powered aircraft, a person must be at least 16 years old and hold at least a current third class medical certificate. A student pilot certificate is valid for 24 months. Student pilots cannot carry passengers, act as pilot in command of an aircraft for compensation or hire, or make international flights (except between certain places in Alaska and Canada). Student pilots may fly only when visibility is at least 3 sm (5 sm at night) and must maintain visual contact with the ground. Student pilots also must receive specific endorsements from a certified flight instructor before flying solo, making cross-country flights, or operating an aircraft in certain types of controlled airspace. Those endorsements must be renewed every 90 days.


sublimation

The changing of ice directly to water vapor, or water vapor to ice, bypassing the liquid state in each process. Snow or ice crystals result from the sublimation of water vapor directly to the solid state.


subsonic

Speeds below the speed of sound, that is, less than Mach 1.


supercharger

A compressor used to increase the density of the air or the air-fuel mixture supplied to a piston engine. As an aircraft climbs, the density of the air entering the engine decreases. Without a supercharger or a tubocharger, an engine gradually loses power. A normally aspirated or "unboosted" engine is most efficient at about 8,000 ft (2,438 m). By the time an aircraft reaches 18,000 ft (5,486 m), the density of the air is about half its value at sea level, and a supercharger or turbocharger is required for efficient operation of the engine.


supercooled water

Water droplets colder than 0 degrees C (32 degrees F). When supercooled droplets strike an exposed object, such as an aircraft's wings and other structures, the impact induces freezing. Supercooled water drops very often are in abundance in clouds at temperatures between 0 and –15 degrees C with decreasing amounts at colder temperatures. However, strong vertical currents may carry supercooled water to great heights where temperatures are much colder. Supercooled water has been observed at temperatures colder than –40 degrees C.


supersonic

Speed that exceeds the speed of sound; Mach 1or greater.


surface inversion

An inversion with its base at the surface, often caused by cooling of the air near the surface as a result of terrestrial radiation, especially at night.


surface visibility

Visibility observed from eye-level above the ground.


tachometer

The instrument that shows the speed of rotation of the engine. It is marked in revolutions per minute (rpm). Engines that produce more than about 180 hp usually have constant speed propellers that can change the blade angle to make more efficient use of engine power throughout a wide range of airspeeds.


takeoff roll

The portion of the takeoff during which the airplane accelerates on the runway.


taxi

To move an aircraft under its own power on the ground.


temperature-dewpoint spread
temperature–dew point spread

The difference between air temperature and dew point temperature. As this difference narrows, clouds and fog are more likely to appear. Pilots must also be aware that even if the spread at ground level is quite large, as temperature drops with altitude the spread narrows, and clouds may form. Pilots should be especially alert for fog whenever the temperature–dew point spread is 5 degrees F (2.8 degrees C) or less and decreasing.


temperature layer

In Flight Simulator, a user-specified weather option that includes the air temperature at a specific altitude and the day–night variation in temperature. You select temperature options in the Advanced Weather dialog box. You can create four temperature layers to see how temperature affects density altitude and aircraft performance.


thermal

A rising column of air caused by the sun heating the earth's surface. Sailplane pilots use thermals to climb or maintain altitude.


threshold

The beginning of the runway surface that is usable for landings. The threshold may coincide with physical end of the runway or be displaced if part of the runway is not usable for landings. The threshold is marked by a single white line on visual runways or by eight parallel white lines arranged in two groups of four on either side of the centerline of an instrument runway.


throttle

The cockpit control that most directly determines the power output of the engine. In a piston engine, the throttle actually controls the amount of air entering the carburetor or induction system. The carburetor or fuel metering system mixes the appropriate amount of fuel with the air to create a combustible mixture. When fully "open" the throttle allows the maximum amount of air to enter the system to produce maximum power. When the throttle is "closed," only a small amount of air enters the system and the engine produces minimum power.


thrust

The forward force generated by a propeller or jet engine that moves the aircraft forward through the air. One of the four major forces, thrust is opposed by drag.


thunderstorm

In general, a local storm invariably produced by a cumulonimbus cloud and always accompanied by lightning and thunder.


trace icing

Icing, regardless of type, that accumulates at about the same rate as it dissipates by sublimation. Trace icing is not considered hazardous, even to aircraft without anti-icing or de-icing equipment, unless the airplane remains in icing conditions for more than one hour.


traffic pattern

The traffic flow prescribed for aircraft landing at and taking off from an airport. Also called a "circuit," chiefly in Britain. A complete landing pattern includes a downwind leg, a base leg, and a final leg. Aircraft taking off typically fly an upwind leg and crosswind leg to depart the airport traffic pattern.


translational lift

In a helicopter, an increase in performance while in forward flight or when hovering in a wind. Air moving horizontally across the rotor disk helps the rotor produce more lift at a given power setting. This effect is generally seen at speeds of less than 10–15 knots. As speed increases, the helicopter experiences effective translational lift.


translating tendency

In a helicopter, the tendency of the aircraft to drift in the direction of tail rotor thrust. For example, U.S.-built helicopters tend to drift right in a hover. Manufacturers compensate for this effect by tilting the main rotor mast slightly to the left or by rigging the cyclic slightly to the left. But the pilot may need to apply slight left cyclic pressure to compensate, especially when operating at a high power setting, such as during a hover or while climbing.


transonic

Speeds close to the speed of sound, in which both subsonic and supersonic airflow conditions exist. Transonic speeds range from about Mach 0.8 to Mach 1.4.


transponder

An airborne transceiver that receives signals from air traffic control (ATC) radar and replies with a preset identification code, or "squawk," set by the pilot. A computer uses the code to display information about each aircraft on an air traffic controller's radar display. Most aircraft today are also equipped with altitude encoders, which transmit the aircraft's altitude along with the transponder code. In the U.S., aircraft operating under visual flight rules (VFR) squawk code 1200 unless they are using air traffic control services and are assigned a specific code by ATC. Under instrument flight rules (IFR), all aircraft are assigned transponder codes by ATC.


tricycle-gear

A landing gear system that includes a nose wheel assembly and two main gear assemblies. Because the center of gravity of a tricycle-gear airplane lies ahead of the main gear, this geometry is much more stable on the ground than the so-called conventional gear or "taildragger" arrangement, which has two main gear assemblies and a tailwheel.


trim

To adjust a movable tab on a control surface, usually the elevator, to relieve pressure on the flight controls. Trim is necessary because as an aircraft changes speed, the amount of air flowing over the control surfaces varies. Without trim, a pilot would have to hold forward or back pressure on the yoke or column to maintain a specific airspeed or pitch attitude. Larger aircraft also have aileron and rudder trim.


tropopause

A thin layer in the upper atmosphere that forms the boundary between the troposphere and stratosphere. The tropopause is usually characterized by an abrupt change of lapse rate. The height of the tropopause varies from about 65,000 ft (19.8 km) over the equator to 20,000 ft (6,096 m) or lower over the poles. Temperature and wind vary greatly in the vicinity of the tropopause. Maximum winds generally occur at levels near the tropopause. These strong winds create narrow zones of wind shear which often generate hazardous high-altitude turbulence.


troposphere

The layer of the atmosphere from the surface to an average altitude of about 7 mi (11 km). Most weather occurs within the troposphere. Temperature generally decreases with altitude in the troposphere at an average rate of 2 degrees C (3.6 degrees F) per 1,000 ft (305 m). The height of the troposphere varies with latitude and seasons. It slopes from about 20,000 ft (6,096 m) over the poles to about 65,000 ft (19.8 km) over the equator. It is higher in summer than in winter. A very thin layer called the tropopause marks the boundary between the troposphere and the next highest layer, the stratosphere.


towering cumulus

A rapidly growing cumulus in which height exceeds width.


tower visibility

Prevailing visibility determined from the control tower.


trade winds

Prevailing, almost continuous winds blowing with an easterly component from the subtropical high pressure belts toward the intertropical convergence zone. They blow northeast in the Northern Hemisphere, southeast in the Southern Hemisphere.


transmissometer

An instrument system that measures the transmission of light through the atmosphere. The transmission value is converted either automatically or manually into visibility, runway visual range (RVR), or both.


transverse flow effect

In a helicopter, a decrease in lift in the aft portion of the rotor disk when in forward flight or when hovering in a wind. At slow speeds, the air moving through the aft portion of the rotor disk is accelerated for a longer time and moves more vertically than the air at the front of the disk. As this accelerated air flows through the aft portion of the disk, it reduces the angle of attack of the rotor blades, decreasing lift produced by the aft part of the rotor disk.


trough

In meteorology, an elongated area of relatively low atmospheric pressure. A trough is usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow.


true airspeed (TAS)

An aircraft's actual speed through the surrounding air. As an aircraft climbs the surrounding air becomes less dense. Therefore indicated airspeed tends to decrease as altitude increases. To determine how fast the airplane is really moving through the air, the pilot calculates TAS based on the aircraft's current pressure altitude and the outside air temperature. A pilot must know TAS to solve navigation problems and file flight plans. As a rule of thumb, at a given indicated airspeed, true airspeed increases about 2 percent for each 1,000 ft (305 m) of altitude. Therefore, an aircraft flying at an indicated airspeed of 100 knots at 10,000 ft (3,050 m) is actually flying at about 120 knots through the air.

By default, airspeed indicators in Microsoft Flight Simulator display indicated airspeed. You can change this setting to display true airspeed on the airspeed indicators. Click Preferences on the Options menu, and on the Instrument tab, clear the Display Indicated Airspeed option.


true altitude

An aircraft's actual height above mean sea level. True altitude is the altitude shown on the altimeter, corrected for non-standard temperature. If the temperature at a particular indicated altitude is warmer than the standard temperature for that altitude, an aircraft's altimeter senses higher than normal pressure and shows an altitude lower than the aircraft is actually flying. If the temperature is cooler than the standard temperature for a particular altitude, the altimeter senses lower than normal pressure and shows an altitude higher than the aircraft is actually flying. Variations from non-standard temperature usually cause only small errors in the altimeter. But when flying without visual references over mountainous terrain or when temperatures aloft differ significantly from the standard temperatures, a pilot should check the aircraft's true altitude to ensure obstacle clearance.


true north

A heading or course pointed directly at the earth's geographic north pole. The earth's magnetic north pole is offset from the geographic north pole, so course lines drawn on a chart are usually referenced to lines of longitude, which indicate true north. To solve navigation problems, pilots convert true courses or headings into magnetic courses and headings that they can fly by referencing the aircraft's compass. The difference between true north and magnetic north is called "variation." The actual value of the variation depends on your location. Many weather reports and forecasts indicate wind direction referenced to true north.


turbocharger

A device on a piston engine that compresses the air entering the engine to maintain power output at high altitudes. Exhaust gas from the engine spins a turbine in the turbocharger at high speed. A compressor attached to the same shaft as the turbine compresses the air entering the intake manifold, "boosting" the engine's power as the density of the outside air decreases with altitude. Turbochargers increase the temperature of the air entering the engine, so pilots must monitor engine temperatures carefully.


turbofan

A jet engine in which most of the air entering the engine is accelerated by a large fan and does not pass through the combustion chamber of the engine. Turbofan engines have largely replaced turbojet engines, in which most of the air entering the engine passes through the combustion chamber. Turbofan engines are much more efficient and significantly quieter than turbojets.


turbojet

A jet engine in which most of air the entering the engine passes through several compressing turbines and then enters the combustion chamber. In a turbojet engine, the exhaust stream produces most of the engine's thrust. Turbojet engines have largely been replaced by more efficient and quieter turbofan engines.


turboprop

A jet engine that drives a propeller to create thrust. Turboprop aircraft are less noisy and burn less fuel than turbojet aircraft, but they are also efficient only at speeds up to about 640 km/h (400 mph). Also called a propjet.


turn coordinator

One of the six primary flight instruments, the turn coordinator shows the rate of turn and the quality of a turn—whether the aircraft is slipping, skidding, or in a balanced turn. In most modern light aircraft the turn coordinator has replaced the "needle and ball," which served the same function.


TWEB

Abbreviation for transcribed weather broadcast. These recorded weather reports and forecasts, prepared by a Flight Service Station (FSS) in the U.S., are broadcast over many navigation facilities, especially VORs. Pilots can monitor TWEB broadcasts while en route to stay up-to-date with the latest weather information.


type certificate

An official document that certifies that an aircraft or engine design has met all the criteria specified in the regulations governing the certification and testing of aircraft. In the U.S., the FAA issues normal, utility, transport, acrobatic, experimental, limited, restricted, and provisional type certificates.


type rating

In the U.S., an authorization added to a pilot certificate that permits a person to act as pilot in command of a specific type of aircraft, usually a large or turbojet-powered aircraft or helicopter. Type ratings are required for all aircraft with a maximum certificated takeoff weight of more than 12,500 lbs (5,670 kg) and all turbojet-powered aircraft, regardless of maximum takeoff weight. A type rating is also required to act as pilot in command of a helicopter if the operation also requires that the pilot hold an airline transport pilot certificate.


ultralight

Single-seat, lightweight aircraft designed for recreational flying. Also known as "microlights," chiefly in Britain. In the U.S., ultralight aircraft are not certified by the FAA and no pilot certificate is required to fly them. According to U.S. regulations (FAR Part 103), an aircraft qualifies as an ultralight if it has an empty weight of no more than 254 lbs (115 kg), if it is equipped with an engine, can carry no more than 5 gallons (18.9 l), cannot fly more than 55 knots in level flight at full power, and has a power-off stall speed no greater than 24 knots.


uncontrolled airspace

Airspace in which air traffic control does not provide services and in which an ATC clearance is not required to operate, regardless of weather conditions.


uncoordinated flight

Slipping or skidding flight caused by yawing forces produced by a turn, by the action of the propeller and slipstream, or by an imbalance of power in a multiengine aircraft. The inclinometer (ball) of the turn coordinator shows whether the yawing forces are properly balanced. If the ball is on the inside of a turn, the airplane is slipping. If the ball moves to the outside of a turn, the airplane is skidding.


undercast

A solid cloud layer as viewed from above the layer.


updraft

A localized upward current of air.


upslope fog

Fog formed when air flows upward over rising terrain and is cooled to or below its initial dew point. Once the upslope wind ceases, the fog dissipates. Unlike radiation fog, upslope fog can form under cloudy skies. It often is quite dense and extends to high altitudes.


UTC (Coordinated Universal Time)

The official time used in air navigation. Also known as Zulu time or GMT. UTC is based on the 24-hour clock; for example, 6:00 P.M. is 1800 hours. Departure and arrival times, air traffic control clearances, the valid time of weather reports and forecasts, and other time-sensitive information in aviation is expressed in UTC.


VASI
VASI (vertical approach slope indicator)

A system of red and white lights near a runway that help pilots determine if they’re on the proper approach path. VASI systems typically include two or three light bars. Each bar usually has two or three lights. If an aircraft is on the proper descent path (usually an angle of about 3 degrees), the pilot sees red lights over white lights. If an aircraft is below the proper descent path, the pilot sees red lights over red lights. The pilot of an aircraft above the proper descent path sees white lights over white lights.


vertical axis

An imaginary vertical line running through the center of an aircraft. Rotation about the vertical axis is called "yaw" and is controlled by the rudder.


vertical speed indicator (VSI)

One of the six basic flight instruments, the vertical speed indicator shows an aircraft's rate of climb or descent, usually in feet per minute. Also known as the rate of climb indicator (RCI) or vertical velocity indicator (VVI). Large aircraft are typically equipped with a sophisticated version of this instrument, called an "instantaneous vertical speed indicator" (IVSI) that reacts immediately to changes in altitude.


vertical stabilizer

The vertical tail surface on an aircraft; sometimes called a "fin." The vertical stabilizer is fixed on most aircraft. With the attached rudder, the vertical stabilizer provides directional stability by controlling movement about the vertical (yaw) axis.


vertigo

A state of temporary spatial confusion resulting from misleading information sent to the brain by various sensory organs; also called "spatial disorientation." Vertigo typically occurs when a pilot cannot see the ground or other references due to clouds or darkness. Turns and other maneuvers can cause the vestibular system—a set of tubes and other sensory organs in the inner ear—to send conflicting signals about the aircraft's orientation and movement. Without visual references to overcome those sensations, the pilot quickly becomes disoriented—unable to tell whether the airplane is flying straight and level, turning, climbing, or descending. To avoid or overcome vertigo, a pilot must rely on the flight instruments to verify the aircraft's attitude and maintain control.


very high frequency (VHF)

The portion of the radio spectrum used in civil aviation for primary radio navigation and communications. Voice communications are assigned frequencies between 118.0 and 136.975 MHz. VORs operate on frequencies between 108.0 and 177.95 MHz.


very high-frequency omnidirectional range (VOR)
very high frequency omnidirectional range (VOR)

A ground-based radio transmitter that projects 360 radials. Some of these radials define airways, but pilots can track any radial to fly a specific path over the ground. VORs operate on frequencies between 108.0 to 177.95 MHz in the VHF band. Although satellite-based navigation systems are rapidly coming into widespread use, VORs remain the primary electronic navigation system in use today.


virga

Water or ice particles falling from a cloud, usually in wisps or streaks, that evaporate before reaching the ground.


visual flight rules (VFR)

The "rules of the road" that govern flight when the visibility and ceiling allow pilots to navigate and avoid obstacles and other aircraft by visual reference. In the U.S., VFR flight is generally permitted when the visibility is at least 3 mi (5 km) and a pilot is able to operate at a safe altitude that is at least 500 ft (152 m) below and 1,000 ft (304 m) above any clouds. In addition, the pilot must remain at least 2,000 ft (608 m) horizontally from any clouds. Specific requirements for VFR depend on the type of airspace, time of day, and height above terrain.


visual meteorological conditions (VMC)

Weather conditions that permit flight under visual flight rules (VFR). In controlled airspace in the U.S., VMC conditions generally mean that the ceiling is at least 1,000 ft (305 m) and flight visibility is at least 3 mi (5 km).


vortices

Rotating air currents created by wings and other airfoils that are producing lift. Vortices are typically created when high-pressure air below a wing circulates toward the low-pressure area above a wing. These vortices are the primary source of induced drag, a byproduct of lift. Vortices created by large, heavy aircraft (called "wake turbulence") are a serious hazard to smaller aircraft, especially during takeoff and landing.


VTOL

Abbreviation for "vertical takeoff and landing," describing aircraft that can take off straight up and land straight down without the need of a runway. The most successful application of VTOL technology, based on the vectored-thrust engine, is the British Harrier jump jet.


wake turbulence

Turbulence caused by a moving aircraft. More specifically, the powerful vortices generated by the wing tips of a large, heavy aircraft.


Walter Beech

1891–1950. American aircraft manufacturer. In 1932 Beech and his wife Olive Ann founded Beech Aircraft, which became a leading producer of light airplanes. Earlier in his aviation career Beech was salesman and test pilot for the Swallow Airplane Company. Failing to persuade the company to adopt metal airframes, he quit and teamed up with Clyde Cessna and Lloyd Stearman to form the Travel Air Manufacturing Company, of which Beech was president.


warm front

Any non-occluded front in which warmer air replaces colder air.


weather areas

In Flight Simulator, regions with similar weather characteristics. Flight Simulator has a global weather area and you can create two local weather areas. You can define the size of the local weather areas and specify the type of clouds, visibility, temperature, wind, atmospheric pressure, and other characteristics of each area.


weathervane effect

The tendency of an aircraft to pivot around its center of gravity and point into the wind.


weight

One of the four basic forces at work on an aircraft in flight. Lift opposes weight (more accurately, the sum of all downward forces), which always acts directly toward the center of the earth. In most calculations, aeronautical engineers assume that all of an aircraft's weight is concentrated at a point called the center of gravity.


William Powell Lear

1902–1978. American designer and manufacturer of business jets. Despite his eighth-grade education, Lear built a successful electronics business. He sold it to finance a new aircraft company, which he started up in 1962 to build business jets based partly on fighters he had helped design for Swiss American Aviation Corp.


wind layer

In Flight Simulator, a user-specified weather option that includes wind speed, direction, gust factor, and turbulence between two altitudes. You select these options on the Wind tab in the Advanced Weather dialog box. You can create two wind layers in each weather area.


wind shear

A sudden, sharp change in wind direction or speed, often associated with a violent, downward burst of air called a microburst or a low-level temperature inversion. Wind shear is particularly dangerous to aircraft during takeoff and landing, where it can cause large variations in airspeed and lead to a rate of sink that can push an aircraft into the ground.


wind tunnel

A device for studying the effects of airflow on aircraft and other vehicles or structures. To simulate the conditions of flight, an aircraft model is mounted in the tunnel and subjected to a stream of air. Sensors gather data on lift and drag, pressure, and other forces acting on the model.


wing loading

An aircraft's weight divided by the area of its wings. For example, an aircraft weighing 4,000 pounds (1,814 kg) that has 400 square feet of wing area has a wing loading of 10 pounds per square foot.


winglets

Vertical extensions added to the ends of a main wing. Winglets reduce induced drag by increasing the effective aspect ratio of the wing, thereby decreasing the intensity of wingtip vortices produced as a byproduct of lift.


wingtip vortex

Rapidly rotating air at an aircraft's wing tips created when a wing produces lift. At the tips, high pressure air below the wing spirals up to the low-pressure area above the wing. Large, heavy aircraft produce intense vortices that are extremely hazardous to small aircraft, especially during takeoff and landing. For example, a small aircraft that flies intoencounters a wing tip vortex can be rolled inverted because the rotation rate of the vortex exceeds the rolling capability produced by the ailerons. Also known as "wake turbulence."


Wright brothers

American aviation pioneers Wilbur (1867–1912) and Orville (1871–1948) Wright made the first powered flight in a heavier-than-air craft. They began experimenting with double-winged kites and gliders and in 1900 made their first test flights at Kitty Hawk. In 1901 they built the first wind tunnel in the U.S., testing over 200 models of wing surfaces. After building an engine for their Flyer, they made their historic flight on December 17, 1903.


yaw

Movement of an aircraft about its vertical axis, as when the nose turns left or right. Along with roll and pitch, yaw is one of an airplane's three basic movements. The vertical stabilizer and rudder are designed to control yaw.


zeppelin

An airship with rigid internal bracing. The helium or hydrogen used to lift a zeppelin is usually contained in large cells. The largest of airships, zeppelins were used as bombers in WWI, but they caused little damage; instead, most were lost to accidents and enemy fire. In 1937 the "Hindenburg" disaster brought a swift end to the use of the rigid airship as a civil transport.


Glossary
A

accelerated stall

ace

active runway

advection

advection fog

advisory circulars (ACs)

aerobatics

aerodynamics

aeronaut

aeronautics

Aérospatiale

aerostats

afterburner

AGL

ailerons

AIM

air mass

air taxi

Air Traffic Control

Airbus Industrie

aircraft

airfoil

airline transport pilot certificate (ATP)

airship

airspace

airspeed

airspeed indicator

Al Mooney

Alberto Santos-Dumont

Alexander Graham Bell

altimeter setting

altocumulus

altocumulus castellanus

altostratus

Amelia Earhart

anemometer

aneroid barometer

angle of attack

angle of incidence

anticyclone

anti-torque pedals

anvil cloud

approach lighting system

Area forecast (FA)

area rule

Aresti notation

aspect ratio

attitude indicator

auto coordination

autogyro

automatic direction finder

automatic pilot

automatic terminal information service

autorotation

avionics

axial-flow

axis indicator

B

balloon (verb)

bank

barnstormer

barometer

barometric altimeter

Bernoulli's Principle

Bill Piper

bleed off

blimp

Boeing

buffet

Buys Ballot's law

C

calibrated airspeed (CAS)

canard

canted gyroscope

cantilever wing

Capt. Chuck Yeager

carburetor

category (aircraft)

ceiling

ceilometer

cell

center of gravity (CG)

centrifugal flow

certified flight instructor certificate

Cessna Aircraft Company

Charles A. Lindbergh

chord

CIGAR check

cirriform

cirrocumulus

cirrostratus

cirrus clouds

Clarence “Kelly” Johnson

class (aircraft)

class (pilot rating)

Class A airspace

Class B airspace

Class C airspace

Class D airspace

Class E airspace

Class G airspace

clear air turbulence (CAT)

clear ice

cloud layer

Clyde Cessna

col

cold front

collective

COM

commercial pilot certificate

composites

condensation

condensation trail

contra-rotating

control yoke

controlled airport

controlled airspace

convection

convective clouds

coordinated flight

Coriolis force

Count Ferdinand von Zeppelin

course deviation indicator

course selector (OBS)

crab angle

critical angle of attack

cruise speed

cumuliform

cumulonimbus clouds

cumulonimbus mamma

cumulus clouds

cyclic

cyclone

D

Daniel Bernoulli

datum

dead reckoning

decision height

density altitude

detonation

dew

dew point

dihedral

dirigible

disk cache

dissymmetry of lift

distance measuring equipment

downdraft

drag

drift

drizzle

dry adiabatic lapse rate

E

effective translational lift

electronic flight instrument system (EFIS)

elevator

empennage

Ernst Mach

Experimental Aircraft Association (EAA)

F

Federal Aviation Administration (FAA)

Federal Aviation Regulations (FARs)

fixed base operator

flaps

flare

Flight Service Station (FSS)

Flight Watch

fly-by-wire

fractus

Frank Whittle

freezing level

front

frontal zone

frontogenesis

frontolysis

fuel injection system

fully articulated rotor system

fuselage

G

general aviation (GA)

glide ratio

glide slope

Greenwich Mean Time (GMT)

ground effect

ground fog

ground loop

ground speed

Gs

GUMPS check

gust

gyro

gyroscopic precession

H

hail

heading

heading indicator

high

high-performance aircraft

hood

horizontal situation indicator (HSI)

horizontal stabilizer

hover

hypersonic

hypoxia

I

ICAO

Igor Sikorsky

Immelmann

indefinite ceiling

indicated airspeed (IAS)

indicated altitude

induced drag

infrared

instrument approach procedure (IAP)

Instrument Flight Rules (IFR)

instrument flight time

instrument landing system (ILS)

instrument meteorological conditions (IMC)

instrument rating

International Terminal Aerodrome Forecast (TAF)

inversion

isobar

isogonic line

isotherm

J

jet stream

joystick

K

katabatic wind

knots

L

landing gear

lapse rate

large aircraft

laser

lateral axis

leading-edge slots

left-turning tendency

lenticular cloud (lenticularis)

Leonardo da Vinci

lift

light aircraft

light gun signals

light icing

light turbulence

lightning

load factor

local weather area

localizer

Lomcovàk

longitudinal axis

loop

low

low G condition

M

Mach 1

Mach number

magnetic compass

magnetic course

magnetic heading

magnetic variation

magneto

maneuvering speed

manifold pressure gauge

marker beacons

Max Immelmann

mean sea level (MSL)

measured ceiling

medical certificate

METAR

microburst

millibar (mb)

mixed ice

mixture control

mmo

moderate icing

moderate turbulence

mountain waves

N

NASA

National Transportation Safety Board (NTSB)

nautical mile (nm)

NAV

Nav

navigation lights

nimbostratus

Ninety-Nines

nondirectional radio beacon (NDB)

nose over

O

obscuration

occluded front

oleo-pneumatic

omni-bearing indicator (OBI)

ornithopters

orographic

Otto Lilienthal

ozone

P

parasite drag

partial obscuration

Patty Wagstaff

Paul Poberezny

Percy Pilcher

performance booster

phonetic alphabet

pilot certificate

pilot in command

pilotage

PIREP

pitch

pitot static system

pitot tube

practical test

precipitation

precipitation-induced fog

pressure altimeter

Pressure Altitude

prevailing easterlies

prevailing visibility

prevailing westerlies

primary flight instruments

private pilot certificate

prognostic chart

Q

R

radar

radar altitude

radarsonde observation

radial

radial engine

radiation fog

radio stack

radiosonde

rate of climb

rating

rawinsonde observation

recreational pilot certificate

relative humidity

relative wind

retreating blade stall

Richard Whitcomb

ridge

ridge lift

rigid rotor system

rime ice

roll

roll cloud

rotary engine

rotation

rotation speed (VR)

rotor cloud

rudder

runway visual range (RVR)

S

sailplane

saturated adiabatic lapse rate

scud

sea fog

semimonocoque

semi-rigid rotor system

settling with power

severe icing

severe turbulence

shock wave

shower

sink rate

skid

slat

slewing

slip

spin

spoilers

spool up

squall

squall line

stability

stability (atmospheric)

stall

stall speed

standard atmosphere

standard conditions

standard pressure

standard rate turn

standard temperature

standardized instrument cluster

stationary front

statute mile (sm)

steady state flight

steam fog

STOL

stratiform

stratocumulus

stratosphere

stratus cloud

student pilot certificate

sublimation

subsonic

supercharger

supercooled water

supersonic

surface inversion

surface visibility

T

tachometer

takeoff roll

taxi

temperature layer

temperature–dewpoint spread

thermal

threshold

throttle

thrust

thunderstorm

tower visibility

towering cumulus

trace icing

trade winds

traffic pattern

translating tendency

translational lift

transmissometer

transonic

transponder

transverse flow effect

tricycle-gear

trim

tropopause

troposphere

trough

true airspeed (TAS)

true altitude

true north

turbocharger

turbofan

turbojet

turboprop

turn coordinator

TWEB

type certificate

type rating

U

ultralight

uncontrolled airspace

uncoordinated flight

undercast

updraft

upslope fog

UTC (Coordinated Universal Time)

V

vertical axis

vertical speed indicator (VSI)

vertical stabilizer

vertigo

Very High Frequency (VHF)

very high-frequency omnidirectional range (VOR)

virga

visual flight rules (VFR)

visual meteorological conditions (VMC)

vortices

VTOL

W

wake turbulence

Walter Beech

warm front

weather areas

weathervane effect

weight

William Powell Lear

wind layer

wind shear

wind tunnel

wing loading

winglets

wingtip vortex

Wright brothers

X

Y

yaw

Z

zeppelin