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pumped out. The atmospheric pressure pressing on the outside of the bag supplies the needed force.
bail out. To jump from an aircraft in flight and use a parachute for descent.
bail-out bottle (oxygen supply). A small high-pressure oxygen bottle attached to a parachute harness. The
bail-out bottle supplies the oxygen used during a parachute descent.
Bakelite. The registered trade name for a phenol resin often used as an electrical insulation.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 60
baking soda. The common term for bicarbonate of soda (NaHCO3). A solution of baking soda and water
can be used to neutralize electrolyte spilled from a lead-acid battery.
balance. A condition of equilibrium, or rest. A lever is in balance when all the forces acting on one side of
the fulcrum, or pivot point, are exactly equal to all the forces acting on the opposite side.
balance cable (airplane control system component). The cable in an airplane control system that ties the
upside of both ailerons together.
When the control wheel is rotated, a cable from the cockpit pulls one aileron down and relaxes the
cable going to the other aileron. The balance cable pulls the other aileron up.
balance chamber (gas turbine engine component). An air chamber inside a gas turbine engine that is
used to absorb some of the thrust load produced by the rotating compressor.
balance checks. Checks performed on rotating components after they have been repaired or overhauled to
determine their condition of static and dynamic balance.
balance panel (airplane control system component). A flat panel hinged to the leading edge of some
ailerons that produces a force which assists the pilot in holding them deflected.
The balance panel divides a chamber ahead of the aileron in such a way that when the aileron is
deflected downward, for example, air flowing over its top surface produces a low pressure that acts on the
balance panel and causes it to apply an upward force to the leading edge as long as it is deflected.
balance point. The point within an object about which all the forces trying to rotate it are balanced. These
forces are equal in amount, but they act on the opposite sides of the balance point.
balance tab (airplane control). A small adjustable tab on a primary control surface of an airplane. The tab
is automatically actuated in such a way it moves in the direction opposite to the direction the control
surface on which it is mounted moves.
Air flowing over the balance tab produces a force on the control surface that reduces the amount
of force needed by the pilot to move the surface.
balance to unbalance transformer. See balun.
balanced actuator (fluid-power actuator). A linear actuator in a fluid-power system that produces the
same amount of force in either direction of piston movement.
The two sides of the piston in a balanced actuator have the same area for the fluid to push against.
balanced amplifier (electronic circuit). An electronic amplifier with two output circuits. The output
signals from these two circuits are equal in amplitude but opposite in phase. A balanced amplifier is also
called a push-pull amplifier.
balanced bridge (electrical measuring circuit). An electrical measuring circuit that uses three known
resistances (R1, R2, and R3) and one unknown resistance (R4). The bridge is balanced (R1 : R2 = R3 : R4)
when no current flows through the indicator.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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balanced control surface (airplane control). A movable primary control surface on an airplane designed
in such a way that aerodynamic forces help the pilot move the surface.
A portion of the surface, called the balance area, extends ahead of the hinge line, and the force of
the air pushing on this balance area aids the pilot in moving the surface.
balanced field length. The runway length in which the takeoff distance is the same as the number of feet
required to accelerate an airplane to a go/no-go speed, decide to abort the takeoff, and come to a complete
stop.
balanced pressure torch (welding torch). A welding torch in which the oxygen and fuel gas are supplied
at the same pressure. Each gas has its own valve to control the amount delivered to the tip.
balanced transmission line (radio-frequency electrical energy transmission). A transmission line
having equal impedance between each conductor and ground, and between each conductor and any other
electronic circuit to which it is connected.
ball bearing. A popular type of antifriction bearing used in many types of machinery.
The outer race, consisting of a grooved hardened steel ring, is mounted in the stationary housing.
And an inner race with a matching groove is mounted on the rotating shaft. Polished, hardened steel balls
　
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