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BADD
avoidance distance measured along track on arrival and
* (D) is same on departure.
2 Bomber Division (R).
3 Biological agent defeat.
4 Behind-armour damage.
BADD Battlefield awareness and data dissemination.
BADGE, Badge Base air-defence ground environment
(Japan).
BADL Bulk acoustic delay line.
BAeA British Aerobatic Association [White Walthan
SL6 3NJ] (UK).
BAeF British Aerophilatelic Federation [Enfield EN3
5NX] (UK).
BAF 1 Bleed-air failure.
2 Incorrectly, Belgian Air Force.
BAFF British air forces in France (1939–40).
baffle 1 Loosely, any device intended to disturb and
impede fluid flow.
2 Shaped plates fixed around and between cylinders of
air-cooled piston engine to improve cooling.
3 Surface, usually in form of a ring, plate or grating,
arranged inside liquid container to minimise sloshing.
4 In two-stroke piston engine, deflector incorporated in
crown of piston.
5 Partial obstruction inside pitot tube to minimise
ingress of liquid or solid matter.
BAFO 1 British Air Forces of Occupation.
2 Best and final offer.
BAG British Airports Group [SBAC, London SW1H
9EU] (UK).
bag See body bag.
baggage Checked-in possessions of a passenger,
normal limits ≤900×700×400 mm (36×28×15 in),
≥350×230×150 mm (14×9×6 in), ≤34 kg (75 lb), no
trailing cord or loose binding nor sharp projections.
bag tank Liquid container, especially fuel tank,
constructed of flexible material not forming part of
airframe.
BAH Belgian Aircraft Homebuilders [office, B-1000
Brussels] (Belgium).
BAI 1 Battlefield air interdiction.
2 Board of Auditors, International (NATO).
BAIG British Aviation Insurance Group.
bail To loan aircraft or other possession, freely but
under contract, to facilitate accomplishment of specific
objective; in particular, loan by owner government of
military hardware to industrial contractor engaged in
particular development programme for that government.
Bailie beam Extra-precise Lorenz beam for Babs.
bail out To abandon dangerously unserviceable aircraft,
esp. in midair, by parachute. Not yet used in connection
with spacecraft.
bailout bottle Emergency personal oxygen supply,
usually high-pressure gox, attached to aircrew harness or
ejection seat.
Bairstow number Mach number.
bakes Back-course (ILS).
Bakelite Trade name for a phenol-formaldehyde resin
plastic.
bake out In high-vacuum technology, heating to
promote degassing.
Baker-Nunn Large optical camera used for tracking
objects in space.
BAL 1 Office of air force training (Switzerland).
ballistic camera
2 Bombe à guidage laser (F).
balance 1 State of equilibrium attained by aircraft or
spacecraft.
2 Mechanism for supporting object under test in windtunnel
and for measuring forces and moments
experienced by it due to gas flow.
3 Mass or aerodynamic surface intended to reduce
hinge moment of control surface.
balance area In aerodynamically balanced control
surface, projected area ahead of hinge axis.
balance beam Large SLAR antenna arranged axially
above fuselage on centreline with mass disposed fore and
aft of c.g.
balance circuit In a WCS, subsystem which prevents, or
warns of impending lateral asymmetry due to unbalanced
weapon load.
balanced approach Optimum approach path referred to
ground, taking in such factors as noise, ATC routing,
cutbacks, land-use planning and preferential-runway
rules.
balanced field length 1 Hypothetical length of runway
for which TODa = EMDa (and sometimes, in addition,
TORa).
2 Under CAR.4b, unfactored TOD to 50 ft following
failure of one engine at V 1 = EMD to and from V 1 , on dry
surface.
balanced modulator Modulator whose output comprises
sidebands without carrier.
balanced signature One which achieves optimal
matching of IRS and RCS.
balanced support Logistic supply based on predicted
consumption of each item.
balanced surface Control surface whose hinge moment
is wholly or partially self-balanced (usually by means of
mass or area ahead of hinge axis or by tabs).
balance rod Mass distributed along or within leading
edge of helicopter rotor blade.
balance station zero Imaginary reference plane perpendicular
to longitudinal axis of aircraft and at or ahead of
nose, used in determinations of mass distribution and
longitudinal balance.
balance tab Tab hinged to, and forming part of, trailing
edge of control surface, and so linked to airframe that it
is deflected in opposition to main surface, and thus
reduces hinge moment. Action is thus similar to that of
servo tab.
bale out See bail out.
ball 1 Small spheroid, or other laterally symmetric
shape, in lateral glass tube of ball-type slip indicator.
2 Arbitrary unit of slip, equal to one ball-width.
ball ammunition Bullets of solid metal, containing no
explosive, pyrotechnic or AP core.
ballast 1 In aerodynamics, mass carried to simulate
payload, and permit c.g. position to be varied (usually in
flight).
2 In aerostats, mass carried for discharge during flight
to change vertical velocity or adjust trim.
ballast carrier In transport aircraft, holder for metal
ballast weights with locking plungers mating with floor
rails.
ball bearing Any shaft bearing in which inner race is
supported and located by hardened spheres.
ball inclinometer Ball turn-and-slip.
ballistic camera Photographic camera which, by means
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