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balanced surface:
aerodynamic balanced surface - A control surface that extends on both sides of the axis of the hinge or pivot or that has auxiliary devices or extensions connected with it in such a manner as to effect a small or zero resultant moment of the air forces about the hinge axis
static balanced surface - A control surface whose center of mass is in the hinge axis

ballonet - A gas-tight compartment of variable volume constructed of fabric and placed within a balloon or airship. It is usually partly inflated with air to compensate for changes of volume in the gas contained in the envelope. (See figs. 3 and 4.)

balloon ceiling - See CEILING, BALLONET

balloon - An aerostat without a propelling system.

captive balloon - A balloon restrained from free flight by means of a cable attaching it to the earth.

ceiling balloon - A small free balloon, whose rate of ascent is known, used to determine ceiling 

free balloon - A balloon, usually spherical, whose ascent and descent may be controlled by releasing ballast or gas and whose direction of flight is determined by the wind.

kite balloon - An elongated form of captive balloon, fitted with lobed to keep it headed into the wind; it usually derives increased lift from the inclination of its axis to the wind.

pilot balloon - A small balloon sent up to show the direction and speed of the wind.

sounding balloon - A small balloon used to send up a meteorograph.

balloon fabric - See Fabric, BALLOON.


mooring band - A band of tape or webbing, over the top of a kite balloon, to which the mooring ropes are attached. It forms part of the mooring harness.

suspension band - A horizontal fabric band, securely fastened to the envelope of a balloon or airship, to which are attached the main suspension lines of the basket or car, or the captive cable of a kite balloon.

trajectory band - A band of webbing carried in a special curve over the surface of the envelope of an airship to distribute the stresses due to the suspension of the car.

bank - The position of an airplane when its lateral axis is inclined to the horizontal. A right bank is the position with the lateral axis inclined downward to the right.

bank - To incline an airplane laterally; i.e., to rotate it about its longitudinal axis.

bank (or banking) indicator - See TURN-AND-BANK INDICATOR

bar, rudder - See RUDDER BAR.

basic load - See LOAD, BASIC

basin, towing - See TANK, SEAPLANE.

basket - The car suspended beneath a balloon for carrying passengers, ballast, etc.

basket suspension - See SUSPENSION BASKET.

beaching gear - An arrangement of wheels to be attached to the hull of a seaplane to permit handling ashore.

beacon - A light, group of lights, or other signaling device, indicating a location or direction.

airport beacon - A beacon light of high candle-power, other than airport or landmark beacon, located on or near an airway for the purpose of indicating the location of the airway.

airway beacon - A beacon light of high candle-power , other than an airport or landmark beacon, located on or near an airway for the purpose of indicating the location of the airway.

auxiliary airport beacon - A beacon light, usually of lower candlepower than the main airport beacon light, located on the airport site to indicate the specific location of an airport that has a separate airport beacon visible at a greater distance to indicate the general location of the airport.

auxiliary airway beacon - A beacon light, usually of lower candlepower than the principal airway beacon lights, used to mark special features of the terrain along an airway or otherwise to supplement the principal airway beacons.

code beacon - A flashing beacon light having a recognizable characteristic of dots and/or dashes by which its individual identity can be established.

landmark beacon - A beacon light, other than an airport beacon or an airway beacon, that serves to indicated a definite geographical location.

beacon, radio-marker - See RADIO-DIRECTIVE DEVICES.

beacon, radio-range- See RADIO-DIRECTIVE DEVICES.

bean direction (stress analysis) - The direction parallel tot he plan of the spar web and the plane of symmetry of an airplane(cf. chord, drag, lift, and side directions).

beam force or component(stress analysis) - A force, or component, in the beam direction; i.e., parallel to the plane of the spar web and the plan of symmetry of airplane (cf. chord. drag, lift, and side forces)/

bearing projector - A fixed directions, projector used in conjunction with a landmark beacon to indicate the direction toward a landing area by means of the direction of its beam.

biplane - An airplane with two main supporting surfaces placed one above the other. 

blade angle - See ANGLE, BLADE.

blade back - The side of a propeller blade that corresponds to the upper surface of an airfoil.