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.
Acceleration
Force involved in overcoming inertia, and which may be defined as a change in velocity per unit of time.
Accessories
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.
Adjustable-pitch propeller
A propeller with blades whose pitch can be adjusted on the ground with the engine not running, but which cannot be adjusted in flight. Also referred to as a ground adjustable propeller. Sometimes also used to refer to constant-speed propellers that are adjustable in flight.
Adverse Loaded CG Check
A weight and balance check to determine that no condition of legal loading of an aircraft can move the CG outside of its allowable limits.
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.
Aerodynamic coefficients
Non-dimensional coefficients for aerodynamic forces and moments.
Aerodynamics
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.
Ailerons
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
A device that is used, or intended to be used, for flight.
Aircraft engine
An engine that is used or intended to be used for propelling aircraft. It includes turbosuperchargers, appurtenances, and accessories necessary for its functioning, but does not include propellers.
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.
Aircraft Specifications
Documentation containing the pertinent specifications for aircraft certificated under the CARs.
Airfoil
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.
Airframe
The fuselage, booms, nacelles, cowlings, fairings, airfoil surfaces (including rotors but excluding propellers and rotating airfoils of engines), and landing gear of an aircraft and their accessories and controls.
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.
Airworthiness
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.
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.
Alternate static source valve
A valve in the instrument static air system that supplies reference air pressure to the altimeter, airspeed indicator, and vertical speed indicator if the normal static pickup should become clogged or iced over.
Alternator/Generator
A device that uses engine power to generate electrical power.
Altimeter
A flight instrument that indicates altitude by sensing pressure changes.
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.
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.
Anti-Icing
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.
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.
Appliance
Any instrument, mechanism, equipment, part, apparatus, appurtenance, or accessory, including communications equipment, that is used or intended to be used in operating or controlling an aircraft in flight, is installed in or attached to the aircraft, and is not part of an airframe, engine, or propeller.
Approved Type Certificate
A certificate of approval issued by the FAA for the design of an aircraft, engine, or propeller.
Arm
(GAMA) The horizontal distance from the reference datum to the center of gravity (CG) of an item. The algebraic sign is plus (+) if measured aft of the datum or to the right side of the center line when considering a lateral calculation. The algebraic sign is minus (-) if measured forward of the datum or the left side of the center line when considering a lateral calculation.
Aspect ratio
Span of a wing divided by its average chord.
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.
Attitude
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.
Autopilot
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.
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