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that is not only physically representative but is also
cleared for flight.
black level In TV system, limit of video (picture) signal
black peaks, below which signal voltages cannot make
electrons reach screen.
black men Ground crew [Schwarze Männer]
(Luftwaffe).
black metal See black aluminium.
blackout 1 In war, suppression of all visible lighting that
could convey information to enemy aircraft.
2 Fadeout of radio communications, including
telemetry, as result of ionospheric disturbances or to
sheath of ionised plasma surrounding spacecraft reentering
atmosphere.
3 Fadeout of radio communications caused by disruption
of ionosphere by nuclear explosions.
4 Dulling of senses and seemingly blackish loss of vision
in humans subjected to sustained high positive acceleration.
In author’s experience, more a dark red, not very
unlike red-out.
blackout block Block of consecutive serial numbers
deliberately left unused.
black picture See black hot.
bladder tank Fluid tank made of flexible material,
especially one not forming part of the airframe.
Blade Bristol Laboratory for Advanced Dynamics
Engineering.
blade 1 Radial aerofoil designed to rotate about an axis,
as in propeller, lifting rotor, axial compressor rotor or
axial turbine. Also see stator *.
2 Rigid array of solar cells, especially one having length
much greater than width.
3 Operative element of windscreen wiper.
blade activity factor Non-dimensional formula for
expressing ability of blade (1) to transmit power; integral
between 0.1 and 0.5 of diameter of chord and cube of
radius with respect to radius. Loosely, low aspect ratio
means high activity factor.
blade aerial Radio aerial, eg for VHF communications,
having form of vertical blade, either rectilinear, tapered or
backswept.
blade angle 1 In propeller or fan blade, angle (usually
acute) between chord at chosen station and plane of
rotation.
2 In helicopter lifting rotor, acute angle between no-lift
direction and plane perpendicular to axis of rotation.
blade angle of attack Angle between incident airflow and
blade (1) tangent to mean chord at leading edge at chosen
station.
blade articulation Attachment to hub of helicopter
lifting rotor blades by hinges in flapping and/or drag axes.
blade back Surface of blade (1) corresponding to upper
surface of wing.
blade beam Hand tool in form of beam incorporating
padded aperture fitting propeller or rotor blade; for
adjusting or checking blade angle.
blade centre of pressure Point through which resultant of
all aerodynamic forces on blade (1) acts.
blade damper Hydraulic, spring or other device for
restraining motion of helicopter lifting rotor blade about
drag (lag) hinge.
bladed spinner Zero stage of part-height blades added to
spinner ahead of fan of turbofan; proposed by Rollsbit
rate
bit rate Theoretical or actual speed at which information
transmission or processing system can handle data.
Measured in bits, kbits, Mbits or Gbits per second.
bitube Single automatic weapon with two barrels.
BIU Bus interface unit.
biz Business (colloq.).
bizav Business aviation.
bizjet Business [executive] jet aircraft.
b J Span of CC blowing slit.
BJA Baseline jamming assets.
BJSD British Joint Service Designation.
BJSM British Joint Services Mission.
BK, bk Break [in transmission].
BKEP Boosted kinetic-energy penetrator.
BKN Broken [clouds].
BKSA British Kite Soaring Association.
BL 1 Buttock line.
2 Base-line (hyperbolic nav).
3 Bulk loader.
4 Between layers.
5 Blowing [DU adds dust, SA sand, SN snow].
BLA Pilotless aerial vehicle (R).
blabbermouth Foam monitor.
BLAC British Light Aviation Centre (50a Cambridge
St. London SW1V 4QQ).
Black 1 SAO security classification.
2 Code, runway is unusable.
black 1 Big error of judgement or faux pas (RAF, as in
“he put up a *”).
2 With all externally visible lighting switched off [interceptor
squadrons] (USAF).
black aluminium Carbon-fibre composite (colloq.).
black ball 1 Traditional form of artificial horizon based
on black hemisphere or bi-coloured sphere.
2 Suspended on mast in signals area: TO and landing
directions may differ.
black body Theoretical material or surface which
reflects no radiation, absorbs all and emits at maximum
rate per unit area at every wavelength for any given
temperature. In some cases wavelength is restricted to
band from near-IR through visible to far-UV.
black-body radiation EM spectrum emitted by black
body, theoretical maximum of all wavelengths possible
for any given body temperature.
black box 1 Avionic equipment or electronic controller
for hardware device or system, removable as single
package. Box colour is immaterial (colloq.).
2 In particular, flight-data or accident recorder, usually
Day-Glo scarlet or orange.
blacker-than-black In TV system, portion of video
signal containing blanking and synchronizing voltages,
which are below black level (with positive modulation)
and prevent electrons from reaching screen.
black hole 1 IRCM design giving engine efflux (esp. of
helicopter) or other heat source greatest protection.
2 Approach to land in near-absence of external visual
cues.
black hot TV or IR display mode giving negative picture
(warm ship looks black against white sea).
blackjack Hand tool for manually forming sheet metal;
has form of flexible (often leather) quasi-tubular bag filled
with lead shot too small to cause local indentations.
Black Label Hardware used in first-build or prototype
bladed spinner
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