Angle of incidence. The acute angle formed between the chord line of an airfoil and the longitudinal axis of the aircraft on which it is mounted. 

Anhedral. A downward slant from root to tip of an aircraft’s wing or horizontal tail surface. 

Annual inspection. A complete inspection of an aircraft and engine, required by the Code of Federal Regulations, to be accomplished every 12 calendar months on all certificated aircraft. Only an A&P technician holding an Inspection Authorization can conduct an annual inspection. 

Anti-ice.  Preventing the accumulation of ice on an aircraft structure via a system designed for that purpose. 

Antiservo tab. An adjustable tab attached to the trailing edge of a stabilator that moves in the same direction as the primary control. It is used to make the stabilator less sensitive. 

Approach lighting system (ALS).  Provides lights that will penetrate the atmosphere far enough from touchdown to give directional, distance, and glidepath information for safe transition from instrument to visual flight. 

Area chart. Part of the low-altitude en route chart series, this chart furnishes terminal data at a larger scale for congested areas. 

Area forecast (FA). A report that gives a picture of clouds, general weather conditions, and visual meteorological conditions (VMC) expected over a large area encompassing several states. 

Area navigation (RNAV).  Allows a pilot to fly a selected course to a predetermined point without the need to overfly ground-based navigation facilities, by using waypoints. 

Arm. See moment arm. 

ARSR.  See air route surveillance radar. 

ARTCC.  See air route traffic control center. 

ASDE.  See airport surface detection equipment. 

ASOS. See Automated Surface Observing System. 

Aspect ratio. Span of a wing divided by its average chord. 

ASR.  See airport surveillance radar. 

Asymmetric thrust. Also known as P-factor. A tendency for an aircraft to yaw to the left due to the descending propeller blade on the right producing more thrust than the ascending blade on the left. This occurs when the aircraft’s longitudinal axis is in a climbing attitude in relation to the relative wind. The P-factor would be to the right if the aircraft had a counterclockwise rotating propeller. 

ATC.  Air Traffic Control. 

ATCRBS. See air traffic control radar beacon system. 

ATIS. See automatic terminal information service. 

Atmospheric propagation delay.  A bending of the electromagnetic (EM) wave from the satellite that creates an error in the GPS system. 

Attitude. A personal motivational predisposition to respond to persons, situations, or events in a given manner that can, nevertheless, be changed or modified through training as sort of a mental shortcut to decision-making. 

Attitude and heading reference system (AHRS). A system composed of three-axis sensors that provide heading, attitude, and yaw information for aircraft. AHRS are designed to replace traditional mechanical gyroscopic flight instruments and provide superior reliability and accuracy. 

Attitude director indicator (ADI).  An aircraft attitude indicator that incorporates flight command bars to provide pitch and roll commands. 

Attitude indicator.  The foundation for all instrument flight, this instrument reflects the airplane’s attitude in relation to the horizon. 

Attitude instrument flying.  Controlling the aircraft by reference to the instruments rather than by outside visual cues. 

Attitude management. The ability to recognize hazardous attitudes in oneself and the willingness to modify them as necessary through the application of an appropriate antidote thought. 

Autokinesis.  Nighttime visual illusion that a stationary light is moving, which becomes apparent after several seconds of staring at the light. 

