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AOPA Student Glossary for General Aviation

100LL—Aviation gasoline, 100 is the octane rating, LL stands for low-lead.

Accident—An occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight and until such time as all such persons have disembarked, and in which any person suffers death or serious injury or in which the aircraft receives substantial damage.

Acrobatic Flight—Intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude or abnormal acceleration not necessary for normal flight.

Aerodrome—A defined area on land or water (including any buildings, installations, and equipment) intended for the arrival, departure, and movement of aircraft.

Aeronautical Chart—Map used in air navigation containing all or part of the following: Topographic features, hazards and obstructions, navigation aids, navigation routes, designated airspace, and airports. Commonly used VFR aeronautical charts are: Sectional Charts, VFR Terminal Area Charts and World Aeronautical Charts (WAC).

Aeronautical Information Manual —Primary FAA publication whose purpose is to instruct airmen about operating in the National Airspace System of the U.S. It provides basic flight information, ATC procedures and general instructional information concerning health, medical facts, factors affecting flight safety, accident and hazard reporting and types of aeronautical charts and their use.

AGL—Above ground level. (See Altitude)

Ailerons—Movable control surfaces at the outer trailing edge of each wing. Controls movement around the longitudinal axis of the aircraft.

Air Traffic Control (ATC)—A service operated by the appropriate authority to promote the safe, orderly, and expeditious flow of air traffic.

Aircraft Owners and Pilots Association (AOPA)—With a membership base of more than 413,000, AOPA is the largest, most influential aviation association in the world. AOPA has achieved its prominent position through effective advocacy, enlightened leadership, technical competence, and hard work. AOPA provides a wide range of member services from representation at the federal, state, and local levels to operational guidance and other technical assistance for pilots and aircraft owners. AOPA has built a service organization that far exceeds any other in the General Aviation community.

Airport—An area on land or water that is used or intended to be used for the landing and takeoff of aircraft and includes its buildings and facilities, if any.

Airport elevation—Highest point of an airport's usable runways measured in feet from mean sea level.

Airport/Facility Directory (A/FD)—Publication designed primarily as a pilot's operational manual containing all airports, seaplane bases and heliports open to the public including communications data, navigational facilities, and certain special notices and procedures. It is issued in seven volumes according to geographical area.

Altitude—Height of a level, point or object measured in feet above ground level (AGL), the altitude expressed in feet measured above ground level or from mean sea level (MSL), the altitude expressed in feet measured from mean sea level. Indicated altitude is the altitude as shown by an altimeter. On a pressure or barometric altimeter it is altitude as shown uncorrected for instrument error and uncompensated for variation from standard atmospheric conditions.

Automatic Terminal Information Service (ATIS)—The continuous broadcast of recorded noncontrol information in selected terminal areas. Its purpose is to improve controller effectiveness and to relieve frequency congestion by automating the repetitive transmission of essential but routine information; e.g., "Los Angeles information alfa. One three zero zero Coordinated Universal Time. Weather measured ceiling two thousand overcast, visibility three, haze, smoke, temperature seven one, dew point five seven, wind two five zero at five, altimeter two niner six. ILS Runway two five left approach in use, Runway two five right closed, advise you have alfa.

Ceiling—The heights above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as "broken," "overcast," or "obscuration," and not classified as "thin" or "partial".

CFI—Certificated Flight Instructor

CFII—Certificated Flight Instructor Instrument, a flight instructor rated to teach instrument flight (flight by instruments only, no outside visual references).

Check ride—An applicant for a pilot's license must take a flight test with either the FAA or a designated examiner. For each new rating (classification), another flight test must be taken.

Controlled Airspace—An airspace of defined dimensions within which air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification. Controlled airspace is a generic term that covers Class A, Class B, Class C, Class D, and Class E airspace. Controlled airspace is also that airspace within which all aircraft operators are subject to certain pilot qualifications, operating rules, and equipment requirements in FAR Part 91 (for specific operating requirements, please refer to FAR Part 91). For IFR operations in any class of controlled airspace, a pilot must file an IFR flight plan and receive an appropriate ATC clearance. Each Class B, Class C, and Class D airspace area designated for an airport contains at least one primary airport around which the airspace is designated (for specific designations and descriptions of the airspace classes, please refer to FAR Part 71.

Controlled airspace in the United States is designated as follows:

  1. CLASS A (formerly PCA—Positive Control Area) generally, that airspace from 18,000 feet mean sea level (MSL) up to and including flight level (FL) 600 (60,000 feet pressure altitude), including the airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska. Unless otherwise authorized, all persons must operate their aircraft under IFR.
  2. CLASS B (formerly TCA Terminal Control Area)—Generally, that airspace from the surface to 10,000 feet mean sea level (MSL) surrounding the nation's busiest airports in terms of airport operations or passenger enplanements. The configuration of each Class B airspace area is individually tailored and consists of a surface area and two or more layers (some Class B airspace areas resemble upside down wedding cakes), and is designed to contain all published instrument procedures once an aircraft enters the airspace. An ATC clearance is required for all aircraft to operate in the area, and all aircraft that are so cleared receive separation services within the airspace. The cloud clearance requirement for VFR operations is "clear of clouds."
  3. CLASS C (formerly ARSA Airport Radar Service Area)—Generally, that airspace from the surface to 4,000 feet above the airport elevation (charted in mean sea level (MSL)) surrounding those airports that have an operational control tower, are serviced by a radar approach control, and that have a certain number of IFR operations or passenger enplanements. Although the configuration of each Class C area is individually tailored, the airspace usually consists of a surface area with a 5 nautical mile (NM) radius, an outer circle with a 10 nm radius that extends from 1,200 feet to 4,000 feet above the airport elevation and an outer area. Each person must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter maintain those communications while within the airspace. VFR aircraft are only separated from IFR aircraft within the airspace.
  4. CLASS D (formerly ATA Airport Traffic Area and CZ Control Zone)—Generally, that airspace from the surface to 2,500 feet above the airport elevation (charted in mean sea level (MSL)) surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored and when instrument procedures are published, the airspace will normally be designed to contain the procedures. Arrival extensions for instrument approach procedures may be Class D or Class E airspace. Unless otherwise authorized, each person must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter maintain those communications while in the airspace. No separation services are provided to VFR aircraft.
  5. CLASS E (formerly General Controlled Airspace)—Generally, if the airspace is not Class A, Class B, Class C, or Class D, and it is controlled airspace, it is Class E airspace. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace. When designated as a surface area, the airspace will be configured to contain all instrument procedures. Also in this class are Federal airways, airspace beginning at either 700 or 1,200 feet AGL used to transition to/from the terminal or enroute environment, enroute domestic, and offshore airspace areas designated below 18,000 feet mean sea level (MSL). Unless designated at a lower altitude, Class E airspace begins at 14,500 feet mean sea level (MSL) over the United States, including that airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska, up to, but not including 18,000 feet mean sea level (MSL), and the airspace above flight level (FL) 600.

Convective—Convective buildup refers to clouds with vertical development; thunderstorms, for example.

Cumulus—clouds with vertical development as opposed to "layered" stratus-type clouds; thunderheads for example.

Dead reckoning—Dead reckoning, as applied to flying, is the navigation of an aircraft solely means of computations based on airspeed, course, heading, wind direction, and speed, ground speed, and elapsed time.

Dewpoint—Temperature at which an air mass must be cooled to become saturated with moisture.

Displaced Threshold—Threshold located at a point on the runway other than the designated beginning of the runway.

Emergency Locator Transmitter (ELT)—Radio transmitter attached to the aircraft structure that operates from its own power source. It aids in locating downed aircraft by radiating a downward sweeping audio tone, 2 to 4 times per second.

Empennage—Any combination of the horizontal stabilizer, elevator, rudder, and vertical fin. It controls the aircraft's pitch and bank.

FARs—Federal Aviation Regulations. The regulations that govern the aviation industry on everything from pilot certification, airspace, and construction of aircraft.

FBO—Fixed base operator. FBOs generally offer flight instruction, sell fuel, and maintain a fleet of aircraft for hire. In addition many of them offer repair service.

Flaps—Devices on the trailing edge of the wings that provide both lift and drag. They are used for landings and sometimes for takeoff and allow an aircraft to fly at a slower airspeed without stalling.

Flight Service Station (FSS)—Air traffic facilities which provide pilot briefing, enroute communications, VFR search and rescue services, assist lost aircraft and aircraft in emergency situations, relay ATC clearances, originate Notices to Airmen, broadcast aviation weather and NAS information, receive and process IFR flight plans, and monitor NAVAIDs. At selected locations, FSS provides Enroute Flight Advisory Service (Flight Watch), takes weather observations, issues airport advisories, and advises Customs and Immigration of transborder flights.

Flight Standards District Office (FSDO)—FAA field office serving an assigned geographical area and staffed with Flight Standards personnel who serve the aviation industry and the general public on matters relating to the certification and operation of air carrier and general aviation aircraft. Activities include general surveillance of operational safety, certification of airmen and aircraft, accident prevention, investigation, enforcement, etc.

Flight Test—Flight to investigate operation/flight characteristics of an aircraft or aircraft component or evaluating an applicant for a pilot certificate or rating.

Flight Watch—Shortened term used in air/ground contacts to identify flight service station providing Enroute Flight Advisory Service.

General Aviation—That portion of civil aviation which encompasses all facets of aviation except air carriers holding a certificate of public convenience and necessity from the Civil Aeronautics Board and large aircraft commercial operators.

Global Positioning System (GPS)—Spacebased radio positioning, navigation and time-transfer system. The system provides highly accurate position and velocity information, and precise time, on a continuous global basis, to an unlimited number of properly equipped users.

Hobbs Meter—An electrically driven meter that records the duration of a flight in hours and fractions of hours.

Hypoxia—Effect of insufficient oxygen to the body. Dangerous when it interferes with a pilot's ability to think and function properly.

Incident—An occurrence other than an accident associated with the operation of an aircraft, which affects or could affect the safety of operations.

Instrument Flight Rules (IFR)—Governs the procedures for conducting instrument flight. Also used to indicate type of flight plan.

Instrument Meteorological Conditions (IMC)—Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling less than the minima specified for VFR.

Long Range Navigation (LORAN)—Electronic navigational system by which hyperbolic lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from two fixed transmitters. Loran A operates in the 1750 to 1950 kHz frequency band. Loran C and D operate in the 100 to 110 kHz frequency band.

MEI—Multi-engine instructor, a CFI rated to teach in a multi-engine aircraft.

MEL—Multiengine Land. An airplane class rating on a pilot certificate.

Military Operations Area (MOA)—Airspace assignment of defined vertical and lateral dimensions established outside Class An airspace to separate/segregate certain military activities from IFR traffic and to identify for VFR traffic where these activities are conducted.

Minimum Equipment List (MEL)—A list of items that may be unserviceable on a type of aircraft under certain stated conditions such as when other identified components are operating normally and weather conditions permit. It is developed from a Master Minimum Equipment List (MMEL) which is published by a regulatory authority in consultation with the aircraft manufacturer and industry.

Mode C—Letter assigned to a specific pulse spacing of radio signals transmitted or received by ground interrogator or airborne transponder components of the Air Traffic Control Radar Beacon System (ATCRBS) for altitude reporting.

MSL—Mean sea level. (See Altitude)

National Airspace System (NAS)—The common network of US airspace; air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and procedures, technical information, and human resources and material. Included are system components shared jointly with the military.

Nautical Mile—one minute of latitude = 6,080 feet.

Notice To Airman (NOTAM)—Notice containing information (not known sufficiently in advance to publicize by other means) concerning the establishment, condition or change in any component (facility, service, procedure of, or hazard in the National Airspace System) when the timely knowledge is essential to personnel concerned with flight operations.

Pilotage—Navigation by ground reference from point to point.

Pilot In Command (PIC)—The person who has final authority and responsibility for the operation and safety of the flight; has been designated as PIC before or during the flight; and holds the appropriate category, class and type rating, if appropriate, for the conduct of the flight.

Pilot Weather Report (PIREP)—Report of meteorological phenomena encountered by aircraft in flight.

Pitot tube—Tube or opening for gathering ram air pressure for use by the airspeed indicator.

Prohibited Area—Designated airspace where aircraft flight is prohibited.

Restricted Area—Airspace designated under FAR Part 73, within which the flight of aircraft, while not wholly prohibited, is subject to restriction. Most restricted areas are designated joint use and IFR/VFR operations in the area may be authorized by the controlling ATC facility when it is not being utilized.

RPM—Revolutions per minute; how fast the engine crankshaft is turning.

Sectional Aeronautical Charts—Designed for visual navigation of slow or medium speed aircraft. Topographic information on these charts features the portrayal of relief and a judicious selection of visual check pints for VFR flight. Aeronautical information includes visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions and related data.

Segmented Circle—System of visual indicators designed to provide traffic pattern information at airports without operating control towers.

SEL—Single Engine Land. An airplane class rating on a pilot certificate.

Special Use Airspace (SUA)—Airspace of defined dimensions identified by an area on the surface of the earth wherein activities must be confined because of their nature and/or wherein limitations may be imposed upon aircraft operations that are not a part of those activities. (See Military Operations Area (MOA), Prohibited Area, Restricted Area, and Warning Area)

Stall—Loss of lift caused by exceeding the critical angle of attack and destroying the smooth flow of air over an airfoil.

Standard Rate Turn—Turn of three degrees per second.

Terminal Area—General term used to describe airspace in which approach control service or airport traffic control service is provided.

Tetrahedron—Device normally located at an airport without a tower. Used as a landing direction indicator. Small end of a tetrahedron points in the direction of landing.

Touch and Go—Operation by an aircraft that lands and departs on a runway without stopping or exiting the runway.

Tower—Terminal facility that uses air/ground communications, visual signaling, and other devices to provide ATC services to aircraft operating in the vicinity of an airport or on the movement area. Authorizes aircraft to land or takeoff at the airport controlled by the tower or to transit the Class D airspace area. May also provide approach control services (radar or nonradar).

Transponder—A device aboard the aircraft that will reply to a ground-based probe signal. This reply makes the aircraft more visible on a controller's radar screen. The signal transmitted by a transponder is referred to as a squawk code.

Uncontrolled Airspace—Class G airspace That portion of the airspace that has not been designated as Class A, Class B, Class C, Class D, and Class E airspace.

Visual Flight Rules (VFR)—Procedures for conducting flight under visual conditions. Term "VFR" is also used to indicate weather conditions equal to or greater than minimum VFR requirements and to indicate type of flight plan.

Visual Meteorological Conditions (VMC)—Meteorological conditions expressed in terms of visibility, distance from cloud and ceiling equal to or better than specified minima for VFR flight.

Vortices—Circular patterns of air created by the movement of an airfoil through the air when generating lift. Vortices from medium to heavy aircraft can be of extremely high velocity and hazardous to smaller aircraft.

Warning Area—An airspace of defined dimensions, extending from 3 nautical miles outward from the coast of the United States, that contains activity that may be hazardous to nonparticipating aircraft. The purpose of such warning areas is to warn nonparticipating pilots of the potential danger. A warning area may be located over domestic, international waters, or both.

Wilco—I have received your message, understand it, and will comply with it.

World Aeronautical Charts (WAC)—Standard series of aeronautical charts, covering land areas at a size and scale convenient for navigation by moderate speed aircraft. Topographic information includes cities and towns, principal roads, railroads, distinctive landmarks, drainage, and relief. Aeronautical information includes visual and radio aids to navigation, airports, airways, restricted areas, and obstructions.