Appendix II
GLOSSARY
Acceleration lag -- in the turbine engine, delay between the time instant power is requested and when
power is available. The time it takes the engine to accelerate and give the required power
increase.
Aerodynamic drag -- force which thrust must overcome to move an aircraft forward. Design can lessen
aerodynamic drag through streamlining. Drag increases with increased speed.
Airbleed actuator -- device that operates the interstage bleed system, to improve compressor acceleration
characteristics by unloading small amounts of compressed air.
Air density -- total mass of air per given volume, the weight of a given volume of air. Air is denser at
lower altitude, at lower temperature, and lower humidity.
Air-fuel ratio -- 15 parts of air to 1 part of fuel by weight, the mixture to be burned in the combustion
chamber.
Air inlet -- large, smooth aluminum duct to conduct the air into the compressor.
Ambient air --
surrounding air.
Angle of attack -- the acute angle formed by the direction of the relative wind and some longitudinal
reference axis of the aircraft.
Annular combustion chamber -- two-part combustion chamber made up of an annular liner and a
housing assembly. The compressed air goes into a ring-shaped space formed by the annular liner
around the turbine shaft rather than into individual combustion chambers. The space between
the outer liner wall and the housing assembly allows the flow of cooling air. Used with axial-
flow and dual compressors.
Annular reverse-flow -- type of gas turbine engine most commonly used in Army aircraft. Air flow
direction is reversed in the combustion area.
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