ANODIZE--To coat a metal by chemical or
ABORT--To cut short or break off an action,
operation, or procedure with an aircraft, guided
missile, or the like, especially because of equip-
ment failure; for example, to abort a mission.
ANTI-ICING--To prevent ice formation on
an aircraft's surface or engines.
of a body, or the rate of such change with respect
APU--Auxiliary power unit.
to speed or direction.
ARTICULATED--A movable joint between
ACCESSORY--A part, subassembly, or
segmented parts. An articulated rotor system is
assembly designed for use in conjunction with or
one whose individual or collective main rotor
to supplement another assembly or unit. For
blades are free to flap, feather, and drag
example, the fuel control is an accessory for a
individually or collectively.
ADDITIVE--A chemical that is added in
ATE--Automatic test equipment.
oil) to create, enhance, or suppress a certain
ATMOSPHERE--The body of air surround-
property or properties in the parent material.
ing the earth. The atmospheric pressure at sea level
is 14.7 psi.
AERODYNAMICS--The science that deals
with the motion of air and other gaseous fluids
ATOMIZE--To reduce a fluid (fuel) to a fine
and the forces acting on bodies in motion relative
spray or mist.
to such fluids.
AUTOROTATION--The process of produc-
AFTERFIRE--The term used when a tail-pipe
ing lift with airfoils that rotate freely and are not
fire develops after engine shutdown.
engine driven. When a helicopter autorotates, the
ALLOY--A substance composed of two or
air flows upward through the rotor system, rather
than downward, as is the case when the rotors are
AMBIENT--Surrounding; adjacent to; next
to. For example, ambient conditions are physical
AVGAS--Aviation gasoline for reciprocating
conditions of the immediate area such as ambient
temperature, ambient humidity, ambient pressure,
AXIS--An imaginary line that passes through
a body about which the body rotates or may be
ANGLE OF ATTACK--The angle at which
assumed to rotate. For example, the horizontal
a body, such as an airfoil or fuselage, meets a flow
axis, the lateral axis, and the longitudinal axis
of air. The acute angle between the chord of an
about which an aircraft rotates.
airfoil and the direction of the relative wind.
BAROMETRIC--The term used for instru-
ANODIC--The term used for the terminal
ments and devices that measure atmospheric
pressure and respond in some way to the changes
to an external point; for example, the negative
terminal on a cell or battery.