aviation weather service. See AWS.
aviators breathing oxygen. Oxygen that has had all of the water and water vapor removed from it.
avionics. The branch of technology that deals with the design, production, installation, use, and servicing of electronic equipment mounted in aircraft.
Avogadro’s principle. A principle of physics which states that under equal pressure and temperature, equal volumes of all gases contain equal numbers of molecules.
avoirdupois weight. The system used in most English-speaking countries for measuring the weight of most substances except drugs and precious metals.
In avoirdupois weight, one pound is equal to 453.6 grams. One ounce is equal to 1/16 pound, and one dram is equal to 1/16 ounce.
AWG (American Wire Gage). The standard used for measuring the diameter of round wires and the thickness of certain nonferrous metal sheets. The American Wire Gage is also known as the Brown and Sharpe Gage.
awl. A smooth, sharp-pointed tool used to make holes in soft materials such as leather, plastic, or wood.
AWS (aviation weather service). A service provided by the National Weather Service (NWS) and FAA which collects and disseminates pertinent weather information for pilots, aircraft operators, and ATC.
Available aviation weather reports and forecasts are displayed at each NWS office and FAA FSS.
axes of an aircraft. Three mutually perpendicular imaginary lines about which an aircraft is free to rotate.
The longitudinal axis passes through the center of gravity of the aircraft from front to rear. The lateral axis passes through the center of gravity from wing tip to wing tip, and the vertical axis passes through the center of gravity from top to bottom.

axial-centrifugal compressor (gas turbine engine component). A combination axial and centrifugal compressor used in a gas turbine engine.
The axial-flow portion of the compressor serves as the low-pressure stage, and the centrifugal portion serves as the high-pressure stage.
axial-flow compressor (gas turbine engine component). A type of compressor used in gas turbine engines in which the air passes through the compressor in essentially a straight line, parallel to the axis of the compressor.
The compressor is made of a number of stages of rotating compressor blades between stages of stationary stator vanes. The compression ratio is determined by the number of stages of compression.
axial-lead resistor (electrical component). A discrete electrical component which provides a given amount of resistance to a circuit.