the Aviation Dictionary

bounce . brake back plate
tapered tap.
bounce - A condition where the breaker points of a
magneto tend to bounce after they close. This is caused
by a weak breaker spring.
boundary layer - 1. The layer of air between the
surface of an object, such as an airfoil, and the
freestream air. At the surface of an object air particles
are slowed to a relative velocity of near zero due to the
viscosity of the air. Surrounding this area, the air
gradually increases in speed until it reaches the
velocity of the freestream air at a given distance from
the surface. 2. The layer of the earth's atmosphere from
surface to approximately 2,000 feet AGL, where
surface friction influences are large.
boundary
.
layer
.
control - A method of removing
random flowing air from the immediate surface of an
airfoil caused by the turbulent flow of the boundary
layer. Boundary layer control is obtained by either
adding energy to it through vortex generators (added
energy delays the airflow from separating from the
airfoil) or by sucking or vacuuming it off through tiny
holes on the surface of the airfoil.
boundary lights - Lights defining the perimeter of an
airport or landing area.
Bourdon tube - The mechanism in a pressure gauge
consisting of a flat or elliptical cross-sectioned tube
bent into a curve or spiral. When pressure is applied,
the tube attempts to straighten. The amount the tube
straightens is proportional to the amount of pressure
inside the tube, and as it straightens, it moves a pointer
across the instrument dial.
bow or camber - The amount that a side of a surface
deviates from being straight.
bow wave - 1. The v-shaped disturbance through a fluid
such as water or air as the result of being displaced by
the foremost point of an object moving through it. 2. A
shock wave that forms immediately ahead of an aircraft
that is flying at a speed faster than the speed of sound.
Bowden cable - A control system that uses a spring
steel wire, enclosed inside a helically wound -wire
casing. used to transmit both pushing and pulling
motion to the device being actuated. Often used as
throttle cables or mixture control cables.
bowline knot - A knot used to tie down an aircraft and
to start the rib-stitching when attaching fabric to an
aircraft structure. A properly tied bowline knot will not
slip yet is easy to untie.
box brake - A metal-forming machine similar to a leaf
(cornice) brake. It is used to form all four sides of a
box by allowing the sides that have been bent up to fit
between the fingers of the clamp while the last bends
are being made. A box brake is also called a finger
brake.
box spar - A design for wood spars in the shape of a
box or a square. The top and bottom of the box are
called the caps of the spar, and the sides of the box are
called the webs of the spar.
box wrench - A wrench with an enclosed end that has
six, eight, or twelve points. It can be used to tighten or
loosen nuts and bolts, and can easily fit into close
spaces and can be used to apply a greater amount of
force than can be applied with an open-end wrench.
boxbeam wing - A wing construction made in the form
of a box, which uses two main longitudinal members
with connecting bulkheads to furnish additional
contour and strength.
boxing of paint - A mixing procedure in which the
paint is poured back-and-forth between two containers
until the pigment and the base paint are completely
mixed.
Boyle's law - A gas law, which states that at a constant
temperature the volume of the gas will vary inversely
as its pressure changes.
brace - A device that holds parts together, or in place.
Something that gives support.
braced wing - A wing that requires external bracing and
is not self-supporting. See cantilever for contrasting
definition.
bracketing - A technique for navigating by VOR in a
crosswind, where the course is maintained by a series
of turns into the crosswind to regain and maintain the
desired course.
brad - A thin wire nail or spike that has a smalldiameter
and a small barrel-shaped head.
braid - The rubber-coated, woven metal fabric
reinforcing cord used to encase hydraulic flex hoses.
braided shield - A covering of braided metal over one
or more insulated conductors to form shielded cable.
This braid intercepts the magnetic field produced by
the alternating current and keeps the field from causing
radio interference.
braiding - Weaving of fibers into a tubular shape
instead of a flat fabric
brake - 1. A device inside an aircraft wheel used to
apply friction to the wheel to slow or stop its rotation.
Wheel brakes slow the aircraft down during taxiing and
landing. Types of brakes used on aircraft are in four
general categories: shoe, expander tube, single disc,
and multiple disc. 2. A metal-working shop tool that is
used to make straight bends across-sheets of metal.
Brakes can be adjusted to make bends with the proper
bend radius and correct number of degrees.
brake back plate - A retainer plate to which the wheel
cylinder and the brake shoes attach.
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