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uckling coefficient
compressive load; state of instability or unstable equilibrium,
but may be purely elastic.
buckling coefficient In an overstressed panel, overall * is
given by K E =(πK/b) 2 , where K is the bending radius of
each skin/stringer element and b is stringer pitch.
BUCS Back-up control system.
buddy Aircraft providing preplanned in flight assistance
to another, specifically by providing fuel to an aircraft of
similar type [as distinct from normal tanker] or by lasermarking
a target. Hence *-* refuelling.
buddy lasing Designation of a target by one aircraft for
attack by another.
buddy pack Flight-refuelling hose reel and drogue packaged
in streamlined container for carriage by standard
weapon rack; thus, aircraft A can refuel buddy B flying
identical aircraft (formerly colloq.).
BUF Back-up facility.
buffer 1 In radio, low-gain amplifier inserted to prevent
interaction between two circuits.
2 Amplifier stage hvaing several inputs, any of which
may be connected to output.
3 In EDP, temporary store used to smooth out information
flow between devices, esp. between I/O and main
processor or core store.
buffer air Air fed under pressure to buffer regions
surrounding gas-turbine shaft-bearing compartments to
ensure that lubricating oil does not seep away through the
labyrinth seals. Hence buffer air seal, buffer compartment.
buffer distance In nuclear warfare, horizontal distance
(expressed in multiples of delivery error) which, added to
radius of safety, will give required acceptable risk to
friendly forces; alternatively, vertical distance (expressed
in multiples of vertical error) added to fallout safe height
to ensure that no fallout will occur.
buffet Irregular rapid oscillation of structure caused by
turbulent wake. * in aeroplanes may be caused by excessive
angle of attack (due to low airspeed, extreme altitude
or excessive g) or, in subsonic aircraft, an attempt to fly at
too high a Mach number.
buffet boundary For any given aircraft and environment,
plot of limiting values of speed and altitude beyond
which buffet will be experienced in unaccelerated flight.
Also defined as condition at which a ‘significant’ region
of separated flow appears.
buffet boundary parameter M 2 C L , product of lift
coefficient and square of Mach number, at which buffet
becomes unacceptable.
buffet inducer Small projection, usually in form of
strake, intended to induce buffet (usually as warning in
advance of dangerous buffet affecting major part of
aircraft).
buffet margin For any given aircraft and environment,
highest vertical acceleration (g) which can be sustained
without exceeding given buffet severity (in some cases
severity is zero).
buffet threshold For any given aircraft and environment,
point at which buffet is first perceptible, expressed in
terms of speed, altitude and vertical acceleration (g).
buffing Process for polishing sheet metal by rotary tool
of soft fabric impregnated with fine abrasive.
BUFR Binary universal format.
bug 1 Heading marker on navigational instrument.
2 Fiducial index, esp. on flight instrument, having
bulk modulus
appearance of *. Can be painted, Chinagraph or removable
by peeling.
3 Clandestine monitoring device, esp. for audiosurveillance.
4 To install and conceal (3).
5 System malfunction or other fault, esp. one not yet
traced and rectified; hence, to debug (colloq.).
Bug-E Battlefield universal gateway equipment, translator
between SADL and other tactical datalinks (USAF).
bug-eye canopy Small canopy (usually two, left and
right) over each projecting pilot’s head in large aircraft
(1942–50).
bugged Value marked by bug (2).
buggying Riding a ground vehicle, eg trike unit, pulled
by kite.
bugle bag Sick bag (colloq. among cabin crew).
bug out Eject (colloq.).
bug speed Speed at which ASI needle passes bug (2),
usually V REF .
BUIC Back-up interceptor control; add-on to SAGE
system [see BICP].
build Growth in received radio signal; opposite of fade.
build standard Detailed schedule of all possible variable
or unresolved items in aircraft or other complex hardware
in stage of development or pre-production. Original **
may list features of airframe, development state of
engines, system engineering and, esp. equipment fitted or
absent; altered as aircraft is modified.
built-in hold Pre-planned hold during countdown to
provide time for defect correction or other activity
without delaying liftoff.
built-up section Structural members having section
assembled from two or more parts, rather than rolled,
extruded, hogged from solid or forged. Reinforced
composites are not regarded as built-up; essentially parts
should be assembled by joints and could be unfastened.
bulb angle, bulb flange Structural sections, usually used
as booms, having circular or polyhedral form. Nearly all
were rolled from strip and had eight to 12 faces after
assembly, complete ** being built up from one to five
segments.
bulk cargo Homogenous cargo, such as coal. Today also
means cargo carried loose; has come to mean cargo or
baggage not contained in standard container or pallet.
bulk erasure Erasure of complete magnetic tape by
powerful field.
bulkhead Major transverse structural member in fuselage,
hull or other axial structure, esp. one forming
complete transverse barrier. Certain *, such as pressure *
in aircraft fuselage and tank * in rocket vehicle, must form
presure-tight seal.
bulk-injection In piston engine injection of fuel into
induction airflow upstream of distribution to individual
cylinders.
bulk loader Self-drive belt conveyor vehicle for loading
bulk cargo.
bulkmeter Instrument, esp. in refuelling of aircraft, for
measuring liquid flow, typically as mass per second or as
summing indication of total mass passed. Some * measure
volume and require density correction for each liquid
handled.
bulk modulus Elastic modulus of solid under uniform
compressive stress over entire surface, as when immersed
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