approximately /.pr.ks.m.tli/
adverb not exactly, around or about .
Approximately 2,000 people work in the airport. (NOTE: Approximately can be shortened to approx or APRX (ICAO).)
approximation /.pr.ks.me..(.)n/
noun a calculation which is not exact but near enough, a rough estimate . an approximation of aircraft height a rough estimate of aircraft height
apron /e.pr.n/ noun an area of tar-mac, concrete, etc., outside a hangar for parking aircraft (NOTE: The US term is ramp.)
APRX abbreviation (ICAO) 1. approxi-mate 2. approximately

APU 22
APU abbreviation auxiliary power unit aquaplaning /kw.ple.n../ noun
sliding in an uncontrolled way over a thin layer of water on the runway .
Aquaplaning is caused by a layer of water between the tyre and the runway.
arbitrary /ɑb.tr.ri/ adjective
decided by chance rather than by care-ful logical thought, happening without planning or at random . The statute mile is an arbitrary unit of measure-ment. (NOTE: The nautical mile is not an arbitrary unit: it is based on calculations which have a wider use. See arc.)
arc /ɑk/ noun part of the circumfer-ence of a circle . A nautical mile is the length of an arc on the Earth’s surface subtended by an angle of one minute at the centre of the Earth. . verb to jump across a gap . The spark arcs from one electrode to another. . The condenser prevents spark plugs from arcing. . gap
Arctic /ɑkt.k/ adjective referring to the area around the North Pole . cold Arctic air cold air from the Arctic . the Arctic Circle a parallel running round the Earth at latitude 66°32N, to the north of which lies the Arctic region . noun . the Arctic the area of the Earth’s surface around the North Pole, north of the Arctic Circle . The aircraft flew over the Arctic.
area /e.ri./ noun 1. a defined part of a surface 2. a region . area forecasts a weather forecast for a region rather than, e.g., an aerodrome
area control service /e.ri. k.n tr.υl sv.s/ noun a unit that provides air traffic control services to flights within the area for which it is responsi-ble

area navigation /e.ri. nv.
e..(.)n/ a method of navigation that permits aircraft to operate on any desired flight path within the area cov-ered by ground-based navigational aids, self-contained navigational aids or a combination of the two. Abbreviation
RNAV argument /ɑjυm.nt/ noun 1. a
factor . QNH is the pressure at station level reduced to sea level using argu-ments of station height and an interna-tional standard atmosphere. 2. a verbal disagreement . to have an argument to disagree openly and verbally with somebody . The investigation revealed that there had been an argument between the commander and the copilot about the advisability of continuing with the final approach to land. 3. a rea-son . One of the arguments in favour of building the new terminal is the increase in opportunities of employ-ment for the local residents.