Aeronautical Information Manual. See AIM.
aeronautics. The branch of science that deals with flight and with the operation of all types of aircraft. Aerodynamics and aerostatics are both branches of aeronautics.
aerosol. A liquid or solid that is divided into extremely fine particles and dispersed into the air.
Smoke is an aerosol of carbon and ash, and a cloud in the sky is an aerosol of water droplets.
Modern aerosol products such as paint, hair spray, and insecticides are usually liquids broken into tiny drops and sprayed into the air by the use of a gaseous propellant such as carbon dioxide, nitrogen, or Freon.
aerospace. The branch of science and technology that deals with travel in the space above the surface of the earth. Aerospace includes travel in the atmosphere, as well as in the vast regions outside of the earth’s atmosphere.
aerospace vehicle. A flight vehicle capable of flight in both the atmosphere surrounding the earth and in the space beyond the atmosphere. The space shuttle is an aerospace vehicle.
aerostat. A device supported in the air by displacing more than its weight of air. Balloons and dirigibles are examples of aerostats.
aerostatics. The branch of science that deals with the flight of lighter-than-air vehicles, such as balloons, dirigibles, or blimps. These vehicles are filled with hot air or with a gas lighter than the air surrounding it. This gas enables the balloon to rise in the air by displacing more than its own weight of air.
Aerostatic lift, which is produced by displacing a mass of air, is different from aerodynamic lift in that it does not require relative motion between the lifting body and the air.
aero-thermodynamic duct. See athodyd.
AFCS (automatic flight control system). The full system of automatic flight control which includes the autopilot, flight director, horizontal situation indicator, air data sensors, and other avionics inputs.
An aircraft with an AFCS can be flown in a completely automatic mode.
“Affirmative” (air traffic control). The term used by ATC for “yes.”
aft. The direction toward the rear of an aircraft.
afterbody (aircraft structure). The rearward portion of an engine nacelle or pod. The portion of the structure that surrounds the tail pipe.
after bottom center (reciprocating engine piston position). The position of the piston in the cylinder of a reciprocating engine after the crankshaft, turning in its normal direction of rotation, has caused the piston to pass the bottom of its stroke and start back up.
afterburner (gas turbine engine component). A device in the exhaust system of a turbojet or turbofan engine, used to increase the thrust for takeoff and for special flight conditions.