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frequencies in a band of frequencies.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 63
bank (airplane flight maneuver). To rotate an airplane about its longitudinal axis, or tilt its wings, by
using the ailerons. An airplane is turned by banking it.
The lift produced by the wings of an airplane always acts perpendicular to the lateral axis of the
airplane. When the airplane is banked, the lift tilts, and its horizontal component pulls the nose of the
airplane around in a curved flight path.
The rudder of an airplane is used only to start the nose moving in the correct direction as the
airplane begins to turn.
bank indicator (aircraft flight instrument). A flight instrument used to show the pilot whether or not the
bank angle being used is correct for the rate of turn being made.
The bank indicator is a curved glass tube partially filled with a clear liquid and containing a black
glass ball. The ball rolls back and forth inside the tube to show the relationship between the centrifugal
force, caused by the rate of turn, and the force of gravity, determined by the angle of bank. The position of
the ball in the tube shows the pilot whether or not the angle of bank is proper for the rate of turn.
When the bank angle is correct for the rate of turn, the force of gravity acting on the ball exactly
balances the centrifugal force, and the ball stays in the center of the tube. If the angle of bank is too steep
for the rate of turn, the ball rolls to the inside of the turn, and if the angle of bank is not steep enough, the
ball rolls to the outside of the turn.
A bank indicator is built into the face of a turn and slip indicator. See turn and slip indicator.
banking. The act of rotating an aircraft about its longitudinal axis.
banner cloud (meteorology). A banner-like cloud streaming downwind from a mountain peak.
bar (unit of pressure). A unit of absolute pressure equal to one million dynes per square centimeter. The
millibar, one thousandth of a bar, is a unit of absolute pressure used in meteorology. The standard absolute
pressure of the atmosphere at sea level is 1013.2 millibars.
bar folder. A type of sheet-metal forming tool used to make bends or folds along the edge of thin sheets of
metal.
bar graph. A form of graph used to show relationships existing between different values. In a bar graph,
each value is represented by a bar of appropriate length. By comparing the lengths of the bars, we can
easily visualize the comparison between the different values.
The bars on a bar graph can be either horizontal or vertical.
bare conductor (electrical wiring). An electrical conductor not covered by any type of insulation.
Bare conductors can be used only where there is no possibility of anything touching them. These
conditions may be found inside the cabinets of certain types of electrical or electronic equipment.
barium. A soft, silvery-white, alkaline-earth, metallic chemical element. Barium’s symbol is Ba, its atomic
number is 56, and its atomic weight is 137.34.
barnstormers. Aviation pioneers who traveled around the country carrying passengers from unimproved
fields. Many of the major airports in the United States were started by barnstormers who leased or bought
some farmer’s field and built it into an airport.
Most of the barnstorming was done between the end of World War I and 1926, at which time the
federal government began to require licenses for airplanes and pilots.
barograph (meteorological instrument). An absolute-pressure measuring instrument (a type of barometer)
that produces a permanent record of the time and the pressure it is measuring.
Barographs are often sealed and are carried aloft to make a permanent record of the altitude that
has been reached by the aircraft.
barometer (pressure measuring instrument). An instrument used to measure the absolute pressure of the
atmosphere. A mercury barometer measures the atmospheric pressure by the height of a column of mercury
held up in a tube by the pressure of the atmosphere. An aneroid (no liquid) barometer measures the pressure
by the amount an evacuated bellows is collapsed by the atmospheric pressure.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 64
barometric altimeter. A pneumatic altimeter. See pneumatic altimeter.
barometric pressure. The pressure produced on the surface of the earth by the weight of the surrounding
air. Barometric pressure is normally measured in inches of mercury, absolute.
barometric scale. A scale on the dial of a sensitive pneumatic altimeter to which the pilot sets the
barometric pressure level from which the altitude shown on the altimeter is measured.
When the scale is set to the standard sea level pressure of 29.92 inches of mercury, the altimeter
　
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