Air Defense Identification Zone. See ADIZ.
air density. The mass of air in a given volume. In the English system of measurements, air density is measured in slugs per cubic foot. Air at standard sea level conditions has a density of 0.002378 slug per cubic foot.
air-dry. To remove moisture from a material by exposing it to the air.
airfield. Any area in which aircraft may land, take off, and park. An airfield may also be called an airport, airstrip, or aerodrome. The term airfield includes the buildings, equipment, and maintenance facilities used to store or service aircraft.
air filter (induction system component). A filter through which air entering the induction system of a reciprocating engine must pass. Filters remove sand and dust, preventing them from entering the engine.
Because of the possibility of the filter being obstructed by ice, provisions are made to bypass it and allow the engine to take in warm, unfiltered air from the engine compartment.
airfoil. Any surface designed to obtain a useful reaction, or lift, from air passing over it. Airplane wings, propeller blades, and helicopter rotors are examples of airfoils.
airfoil characteristic curves. A set of curves for an airfoil section plotted from wind tunnel data that shows the effect of angle of attack on the coefficient of lift, coefficient of drag, lift over drag ratio, and the movement of the center of pressure.
airfoil profile. The outline of an airfoil section.
airfoil section. The cross-sectional shape of an airfoil, viewed as if it were cut through in a fore-and-aft plane.
airframe. 14 CFR Part 1: “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.”
airframe mechanic. A person holding a certificate issued by the Federal Aviation Administration that authorizes him or her to perform maintenance and inspections on the airframe of FAA-certificated aircraft.
air-fuel mixture ratio. The ratio of the weight of the air to that of the fuel in the mixture being fed into the cylinders of a reciprocating engine.
air impingement (aircraft finish defect). A fault resembling haze in an enamel or lacquer finish of an aircraft. Air impingement is caused by microscopic-sized bubbles in the finish that form when the finishing material is applied using too high an atomizing air pressure.
air impingement starter (gas turbine engine starter). A type of starter used on some gas turbine engines in which a stream of high-pressure compressed air is directed onto the blades of the compressor or turbine to rotate the engine for starting.
air inlet duct (turbine engine component). The portion of the aircraft ahead of the engine compressor that takes the air into the aircraft and directs it into the engine at the correct speed and direction.
airline. A company or organization that operates aircraft for the transportation of persons or cargo for compensation or hire.