the Aviation Dictionary

bisector of a line - A position on a line that divides it
into two segments of equal length.
bisector of an angle - A line that divides an angle into
two equal angles.
bismaleimide (BMI) - In composites, a polyimide resin
that cures at a very high temperature, and has a very
high operating temperature range in the 550 - 600' F
range, and some around the 700°F range. These are
more difficult to cure because of the moisture
emissions during the cure may cause voids or
delaminations.
bismuth - A hard, brittle, grayish-white, trivalent,
metallic chemical element that has the symbol Ri and
atomic number 83. Used as an alloying agent for
changing the characteristic of certain metals. It is also
used to dope silicon or germanium to make a P-type
semiconductor material.
bistable - A condition that exists in a circuit in which
either of two conditions may exist as a steady state.
bistable circuit - A circuit that has two stable
conditions. The circuit will operate in the condition
selected until it is intentionally changed.
bistable multivibrator - An oscillator circuit that uses
two transistors ofwhich only one transistor conducts at
a time. When the first transistor stops conducting, the
second transistor automatically starts to conduct.
bistatic radar - A radar system that uses separate
transmitter and receiver antennas.
bit - One unit of a binary number.
bitumen - An asphaltic residue that remains after the
fractional distillation of crude oil. Asphalt and tar are
two commonly used bitumens.
bituminous paint - A heavy, thick, tar-based paint used
as an acid-resistant paint to reduce the corrosive action
of fumes and spilled electrolytes in battery
compartments.
bisector of a line . blade cuff
blade - In gas turbine engines, a rotating airfoil utilized
in a compressor as a means of compressing air or in a
turbine for extracting energy from the flowing gases.
blade alignment - In rotorcraft, an adjustment
procedure, used on semi-rigid rotor systems, to place
the blades in proper positions on the lead-lag axis of
the rotor system. Blade alignment is sometimes
referred to as chordwise balance.
blade angle - The angle between the plane of propeller
rotation and the face of the propeller blade.
blade angle check and adjusting - A method used to
check the blade-angle setting at a predetermined blade
station. The blade angle is checked using a device
called a Universal Protractor.
blade antenna - A wide-band, quarter-wavelength
antenna used on aircraft for communications or
navigation in the ultra-high or very-high frequency
bands.
blade back - The cambered side of a propeller blade
that corresponds to the curved upper surface of an
airfoil, similar to that of an aircraft wing. The opposite
side of the blade face.
blade base - The portion of the blade where the
contoured section meets the root area. Also referred to
as the blade platform.
blade beam - A paddle-shaped lever having a slot
shaped to fit the cross section of a propeller blade.
Used for manually turning propeller blades. Blade
beams are also referred to as blade wrenches.
blade blending - A process used to remove small
shallow scratches or dents of turbine blades using mild
abrasive materials and sanding techniques. Blending
requires maintaining the original contour and shape of
the blade within prescribed limits.
blade butt - The root end of a propeller blade that fits
into the hub of a propeller assembly.
blade chamber - The top or convex side of a rotating
airfoil such as a compressor blade.
black box - A piece of electronic equipment that may be
removed and replaced as a single - unit.
blade chord line - An imaginary line drawn through the
black ice - Transparent ice that forms on black
blade from the leading edge to the trailing edge.
uavement, making - it difficult to see. It may be caused
by the refreezing of melted water or from freezing rain. blade climbing - In rotorcraft, a condition when one or
Also a thin sheet of transparent ice that forms on the more blades are not operating in the same plane of
surface of water.
rotation during flight. Might not exist during ground
black light - Ultraviolet light with rays that are in the
operation.
lower end of the visible spectrum. While more or less blade coning - In rotorcraft, an upward sweep of rotor
invisible to the human eye, black lights excite, or make blades as a result of lift and centrifugal force.
visible, certain materials such as fluorescent dyes.
blade cross over - See blade climbing.
bladder-@~e - A neoprene fabric
bag installed in a portion of the aircraft structure to
blade cuff A metal, wood, or plastic fairing installed
form a cell and used to hold fuel.
Aircraft Technical Book Company
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around the shank of a propeller blade to carry the
airfoil shape of the blade all of the way to the propeller