Aeronautical chart. A 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. 

Aeronautical decision-making (ADM).  A systematic approach to the mental process used by pilots to consistently determine the best course of action in response to a given set of circumstances. 

Agonic line. An irregular imaginary line across the surface of the Earth along which the magnetic and geographic poles are in alignment, and along which there is no magnetic variation. 

Ailerons. Primary flight control surfaces mounted on the trailing edge of an airplane wing, near the tip. Ailerons control roll about the longitudinal axis. 

Aircraft. A device that is used, or intended to be used, for flight. 

Aircraft altitude. The actual height above sea level at which the aircraft is flying. 

Aircraft approach category.  A performance grouping of aircraft based on a speed of 1.3 times the stall speed in the landing configuration at maximum gross landing weight. 

Air data computer (ADC). An aircraft computer that receives and processes pitot pressure, static pressure, and temperature to calculate very precise altitude, indicated airspeed, true airspeed, and air temperature. 

Airfoil. Any surface, such as a wing, propeller, rudder, or even a trim tab, which provides aerodynamic force when it interacts with a moving stream of air. 

Air mass. An extensive body of air having fairly uniform properties of temperature and moisture. 

AIRMET.  Inflight weather advisory issued as an amendment to the area forecast, concerning weather phenomena of operational interest to all aircraft and that is potentially hazardous to aircraft with limited capability due to lack of equipment, instrumentation, or pilot qualifications. 

Airplane. An engine-driven, fixed-wing aircraft heavier than air that is supported in flight by the dynamic reaction of air against its wings. 

Airplane Flight Manual (AFM). A document developed by the airplane manufacturer and approved by the Federal Aviation Administration (FAA). It is specific to a particular make and model airplane by serial number and it contains operating procedures and limitations. 

Airplane Owner/Information Manual. A document developed by the airplane manufacturer containing general information about the make and model of an airplane. The airplane owner’s manual is not FAA approved and is not specific to a particular serial numbered airplane. This manual is not kept current, and therefore cannot be substituted for the AFM/POH. 

Airport diagram.  The section of an instrument approach procedure chart that shows a detailed diagram of the airport. This diagram includes surface features and airport configuration information. 

Airport/Facility Directory (A/FD). See Chart Supplement U.S. 

Airport surface detection equipment (ASDE).  Radar equipment specifically designed to detect all principal features and traffic on the surface of an airport, presenting the entire image on the control tower console; used to augment visual observation by tower personnel of aircraft and/or vehicular movements on runways and taxiways. 

Airport surveillance radar (ASR).  Approach control radar used to detect and display an aircraft’s position in the terminal area. 

Airport surveillance radar approach.  An instrument approach in which ATC issues instructions for pilot compliance based on aircraft position in relation to the final approach course and the distance from the end of the runway as displayed on the controller’s radar scope. 

Air route surveillance radar (ARSR).  Air route traffic control center (ARTCC) radar used primarily to detect and display an aircraft’s position while en route between terminal areas. 

Air route traffic control center (ARTCC).  Provides ATC service to aircraft operating on IFR flight plans within controlled airspace and principally during the en route phase of flight. 

Airspeed. Rate of the aircraft’s progress through the air. 

