anechoic room (radar test facility). A special room whose walls are covered with radar absorbing materials. Anechoic rooms are used for testing radar components in an environment in which there are no echoes.
anemometer. An instrument used to measure the velocity of moving air. A cup-type anemometer uses a series of hemispherical metal cups mounted on arms on a shaft. The air blows the cups and rotates the shaft. A counter measures the number of revolutions the shaft makes in a given period of time and converts this into wind speed.
A fan-type anemometer uses a small, multibladed propeller, turned by the air moving through it. The faster the air flows, the faster the fan turns.
The dial on the anemometer may be marked in feet per second, meters per second, kilometers per hour, miles per hour, or knots.
aneroid. The sensitive component in an altimeter or barometer that measures the absolute pressure of the air. An aneroid is a sealed, flat capsule made of thin disks of corrugated metal soldered together and evacuated by pumping all of the air out of it.
Evacuating the aneroid allows it to expand or collapse as the air pressure on the outside changes. The pressure of the air can be found by measuring the amount the aneroid expands or collapses.
aneroid barometer. An instrument that measures the absolute pressure of the atmosphere by balancing the weight of the air above it against the spring action of a specially shaped evacuated metal bellows.
AN flared tube fittings. A series of flare-type fittings for fluid lines installed in an aircraft. AN fittings have a 37° flare angle and a short shoulder between the ends of the flare cone and the first thread.