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lind rivet
blind rivet Rivet inserted and closed with no access to far
side of joint. Apart from explosive and rare magneticpulse
types, invariably tubular.
blind speed effect Characteristic of Doppler MTI
systems used with radars having fixed PRF which makes
them blind to targets whose Doppler frequencies are
multiples of PRF (see staggered PRF).
blind spot 1 Not reached by radio or radar, for whatever
reason.
2 Region of airfield hidden from tower.
blind toss Programmed toss without acquisition of
target (eg on DR from an offset).
blind transmission Station called cannot talk back.
bling Monolithic bladed ring forming one rotor stage of
a compressor or turbine [gas-turbine].
blink 1 Of light or other indicator, to be illuminated and
extinguished, or to present black/white or other
contrasting colour indication, more than 20 times per
minute.
2 In aircraft at night in VFR, manually to switch off
navigation lights (typically, twice in as many seconds) as
acknowledgement of message.
blinker Light or indicator that blinks (1), eg to confirm
oxygen feed. See doll’s eye.
Blip, blip Background-limited IR performance.
blip 1 Visible indication of target on radar display. Due
normally to discrete target such as aircraft or periscope of
submarine; in ground mapping mode, term used only to
denote strong echo from transponder.
2 Spot, spike or other indication on CRT due to signal
of interest.
3 To control energy input to early aeroplane by
switching ignition on and off as necessary (normally, on
landing approach).
4 To operate bang/bang control manually (eg, electric
trim).
blip driver Operator of synthetic trainer for SSR or other
surveillance radar with rolling ball or other means of
traversing system co-ordinates to give desired blip (1)
position and movement (colloq.).
blip/scan ratio Also written blip: scan, an expression for
probability of detection of a target by radar.
blisk Axial turbine rotor stage (rarely, compressor
stage) in which disc [US = disk] and blades are fabricated
as single piece of material.
Bliss Bi-level integrated system synthesis.
blister 1 Streamlined protuberance on aerodynamic
body, usually of semicircular transverse section and often
transparent to selected EM wavelengths.
2 See blister spray.
blister aerial Aerial projecting from surface of aircraft
and faired by dielectric blister.
blister hangar Prefabricated and demountable hangar
having arched roof and fabric covering.
blister spray Arching sheet of water thrown up and
outwards above free water surface on each side of planing
hull or float. Compared with ribbon spray, has lower
lateral velocity, rises higher, is clear water rather than
spray, and is much more damaging.
blister spray dam Strong strip forming near-vertical wall
projecting downwards along forebody chine of hull or
float.
blivet Flexible bag for transporting fuel, usually as helicopter
slung load.
blocking up
BLK 1 Block.
2 Black.
BLM 1 Background luminance monitor.
2 Bureau of Land Management, Federal agency
responsible for firefighting in wild regions (US).
BLN Balloon.
BLO Below clouds (ICAO).
blob Local atmospheric inhomogeneity, produced by
turbulence, with temperature and humidity different from
ambient. Can produce angels (2).
block 1 In quantity production, consecutive series of
identical products having same * number. In World War 2
aircraft production a * might number several hundred;
with large spacecraft and launch vehicles, fewer than ten.
In general, products of two * normally differ as result of
incorporation of engineering changes.
2 In research, groups of experimental items subjected to
different treatment for comparative purposes.
3 In EDP, group of machine words considered as a unit.
4 In aircraft (usually commercial) operation, chocks
(real or figurative) whose removal or placement defines
the beginning and end of each flight.
blockbuster Large thin-case conventional bomb [British
term for German = land mine, 1940–45] (colloq.).
block check sequence Cyclic code used as reference bits
in error-detection procedure.
block construction Arrangement of gores of parachute
such that fabric warp threads are parallel to peripheral
edge.
block diagram Pictorial representation of system, other
than purely electrical or electronic circuit, in which lines
show signal or other flows between components, depicted
as blocks or other conventional symbols.
blocker See inlet *.
blocker door In installed turbofan engine, hinged or
otherwise movable reverser door (normally one of peripheral
ring) which when closed blocks fan exit duct and
opens peripheral exits directing airflow diagonally
forward.
block fuel Fuel burned during block time.
block-hour cost DOC for one hour of block time.
blockhouse Fortified building close to launch pad for
potentially explosive vehicles, from which human crew
manage launch operations or perform other duties (eg
photography).
block in To park transport aircraft at destination. Term
spread from commercial to military transport use.
blocking 1 In wind tunnel, gross obstruction to flow
caused by shockwaves at Mach numbers close to 1, unless
throat and working section designed to avoid it (see
choking).
2 Use of struts and wedges to prevent movement of
loose cargo or cargo inside container.
3 Use of form block.
blocking capacitor Capacitor inserted to pass AC and
block DC.
blocking layer Barrier layer in photovoltaic (ie solar)
cell.
blocking oscillator Any of many kinds of oscillator
which quench their output after each alternate half-cycle
to generate sawtooth waveform.
blocking up To use shaped masses behind sheet metal
being hammered.
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