Aeronautical Terms beginning with A

Absolute Altitude

The vertical distance of an airplane above the terrain, or above ground level (AGL).

Absolute Ceiling

The altitude at which a climb is no longer possible.

Accelerate-Go Distance

The distance required to accelerate to V1 with all engines at takeoff power, experience an engine failure at V1, and continue the takeoff on the remaining engine(s). The runway required includes the distance required to climb to 35 feet by which time V2 speed must be attained.

Accelerate-Stop Distance

The distance required to accelerate to V1 with all engines at takeoff power, experience an engine failure at V1, and abort the takeoff and bring the airplane to a stop using braking action only (use of thrust reversing is not considered).


Force involved in overcoming inertia, and which may be defined as a change in velocity per unit of time.


Components that are used with an engine, but are not a part of the engine itself. Units such as magnetos, carburetors, generators, and fuel pumps are commonly installed engine accessories.

Adjustable Stabilizer

A stabilizer that can be adjusted in flight to trim the airplane, thereby allowing the airplane to fly hands-off at any given airspeed.

Adverse Yaw

A condition of flight in which the nose of an airplane tends to yaw toward the outside of the turn. This is caused by the higher induced drag on the outside wing, which is also producing more lift. Induced drag is a by-product of the lift associated with the outside wing.

Aerodynamic Ceiling

The point (altitude) at which, as the indicated airspeed decreases with altitude, it progressively merges with the low speed buffet boundary where pre-stall buffet occurs for the airplane at a load factor of 1.0 G.


The science of the action of air on an object, and with the motion of air on other gases. Aerodynamics deals with the production of lift by the aircraft, the relative wind, and the atmosphere.


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

Air Start

The act or instance of starting an aircraft’s engine while in flight, especially a jet engine after flameout.

Aircraft Logbooks

Journals containing a record of total operating time, repairs, alterations or inspections performed, and all Airworthiness Directive (AD) notes complied with. A maintenance logbook should be kept for the airframe, each engine, and each propeller.


An airfoil is 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.


A sound acquaintance with the principles of flight, the ability to operate an airplane with competence and precision both on the ground and in the air, and the exercise of sound judgment that results in optimal operational safety and efficiency.

Airmanship Skills

The skills of coordination, timing, control touch, and speed sense in addition to the motor skills required to fly an aircraft.

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/Facility Directory

A 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. This publication is issued in seven volumes according to geographical area. (Renamed to Chart Supplement)


A condition in which the aircraft conforms to its type certificated design including supplemental type certificates, and field approved alterations. The aircraft must also be in a condition for safe flight as determined by annual, 100 hour, preflight and any other required inspections.

Airworthiness Certificate

A certificate issued by the FAA to all aircraft that have been proven to meet the minimum standards set down by the Code of Federal Regulations.

Airworthiness Directive

A regulatory notice sent out by the FAA to the registered owner of an aircraft informing the owner of a condition that prevents the aircraft from continuing to meet its conditions for airworthiness. Airworthiness Directives (AD notes) must be complied with within the required time limit, and the fact of compliance, the date of compliance, and the method of compliance must be recorded in the aircraft’s maintenance records.

Alpha Mode Of Operation

The operation of a turboprop engine that includes all of the flight operations, from takeoff to landing. Alpha operation is typically between 95 percent to 100 percent of the engine operating speed.

Alternate Air

A device which opens, either automatically or manually, to allow induction airflow to continue should the primary induction air opening become blocked.

Alternate Static Source

A manual port that when opened allows the pitot static instruments to sense static pressure from an alternate location should the primary static port become blocked.


A device that uses engine power to generate electrical power.


A flight instrument that indicates altitude by sensing pressure changes.

Altitude (AGL)

The actual height above ground level (AGL) at which the aircraft is flying.

Altitude (MSL)

The actual height above mean sea level (MSL) at which the aircraft is flying.

Altitude Chamber

A device that simulates high altitude conditions by reducing the interior pressure. The occupants will suffer from the same physiological conditions as flight at high altitude in an unpressurized aircraft.

Altitude Engine

A reciprocating aircraft engine having a rated takeoff power that is producible from sea level to an established higher altitude.

Angle Of Attack

The acute angle between the chord line of the airfoil and the direction of the relative wind.

Angle Of Incidence

The angle formed by the chord line of the wing and a line parallel to the longitudinal axis of the airplane.

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.


The prevention of the formation of ice on a surface. Ice may be prevented by using heat or by covering the surface with a chemical that prevents water from reaching the surface. Anti-icing should not be confused with deicing, which is the removal of ice after it has formed on the surface.


The position of an aircraft as determined by the relationship of its axes and a reference, usually the earth’s horizon.

Attitude Indicator

An instrument which uses an artificial horizon and miniature airplane to depict the position of the airplane in relation to the true horizon. The attitude indicator senses roll pitch, which is the up and down as well as movement of the airplane’s nose.


This is caused by staring at a single point of light against a dark background for more than a few seconds. After a few moments, the light appears to move on its own.


An automatic flight control system which keeps an aircraft in level flight or on a set course. Automatic pilots can be directed by the pilot, or they may be coupled to a radio navigation signal.

Axes Of An Aircraft

Three imaginary lines that pass through an aircraft’s center of gravity. The axes can be considered as imaginary axles around which the aircraft turns. The three axes pass through the center of gravity at 90°angles to each other. The axis from nose to tail is the longitudinal axis, the axis that passes from wingtip to wingtip is the lateral axis, and the axis that passes vertically through the center of gravity is the vertical axis.

Axial Flow Compressor

A type of compressor used in a turbine engine in which the airflow through the compressor is essentially linear. An axial-flow compressor is made up of several stages of alternate rotors and stators. The compressor ratio is determined by the decrease in area of the succeeding stages.

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