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strobe marker
5 To select particular portion of waveform timebase or
other time subdivision in cyclic phenomenon.
6 Stroboscope.
strobe marker Small bright spot, short gap or other
discontinuity on radar timebase or other portion of
cyclically scanned display to indicate portion receiving
special attention.
strobe pulse See strobe marker.
strobe timebase Small section of timebase containing
target blip, Loran signal or other object of interest which is
extracted by strobe marker and expanded to fill original
timebase width. In some cases process can be repeated,
giving expanded **.
strobe unit In missile guidance system, generates strobing
pulses which search and lock-on to target reflections and
supply target range and relative velocity to guidance
computer.
Strobokerr Camera for ultrafast photography in which
incoming scene passes through Kerr cell, which divides it
into pulses of light so brief that clear non-smeared images
are projected on to film revolving at high speed inside drum.
stroboscope Instrument for apparently bringing rotating
or oscillating objects to rest by intermittent phased illumination,
eg for inspection of deflection under high-speed
operation or to determine rpm or Hz.
stroke 1 Linear distance moved by piston of piston engine
from TDC to BDC or vice versa.
2 One complete translation of piston from TDC to BDC
or vice versa, performing particular operation; thus inlet or
induction *, compression *, power * and exhaust *.
3 Linear or angular distance travelled by electron or
other beam forming timebase or any other electronic
display.
4 Linear or angular distance travelled by output of actuator.
5 One major ‘flash’ making up flash of lightning,
normally repeated every 38-45 ms until discharge complete.
6 Basic element of *-generated writing.
stroke font Total repertoire of alphanumeric characters
possible with particular stroke-generated writing system.
stroke-generated writing Major branch of alphanumerics
for electronic displays in which each character is assembled
from one or more straight-line strokes. Simplest format is
7-segment, also called DHW (double-hung window), all
segments of which are used in figure 8 (this is common in
LED and LCD displays for minimum cost, eg watches);
another common system is 14 or 16-bit starburst, and best
results are yielded by multi-stroke systems using five
lengths and up to 40 orientations.
stroking Correct cycling of pump plungers over full
stroke, eg in variable-displacement pump with swash drive
from one end.
strongback Structural member added over large surface
to provide rigidity in bending and torsion, eg across large
rotodomes.
strongpoint See hardpoint.
strontium Sr, soft, reactive, silvery metal, many uses as
element and compounds, Sr-90 dangerously radioactive.
Density 2.5, MPt 769°C.
strop 1 Flexible loop connecting deck accelerator (catapult)
to aircraft not fitted with nose towbar.
2 Length of webbing connecting static line of airdrop
load to anchor cable (DoD).
3 Also see suspension *.
strutjet
Strouhal number Constant for particular bodies in fluid
flows giving rise to street of vortices and from which
frequency of shedding can be derived; S = fD/V where f is
frequency, D is diameter of cylinder or wire and V is
velocity; for regular cylinder S is 0.2 for R between 10 3 and
2 × 10 5 .
structural aspect ratio See aspect ratio.
structural augmentation roadmap Schedules for strengthening
tired airframes (USAF, ANG).
structural damping Total damping of assembled
structure.
structural design Total task of designing structure.
structural element Subdivisons of structure such as a spar,
rib or frame, which may themselves be assembled from
smaller structural members.
structural factor Seldom used ratio of structure mass to
sum of structural plus propellant mass for rocket vehicle;
mass ratio more common.
structural failure Breakage under load.
structural limit Greatest weight (mass) at which aircraft
can show compliance with structural requirements, usually
MRW.
structural machine screw HT-steel machine screw (term
often synonymous with bolt) with unthreaded shank
portion below head.
structural member Portion of structure, esp. any part
important in bearing loads; can be single piece of material
or assembly, and demarcation with structural element is
blurred.
structural merit index Ratio E/ρ, modulus divided by
density.
structural-mode control system Flight-control subsystem
whose purpose is to reduce stresses in structure during flight
through gusts and other turbulence, esp. in dense air, or to
reduce vertical accelerations experienced by crew compartment.
Requires vertical-acceleration sensor and separate
horizontal (occasionally inclined or vertical) surfaces to
apply required countering forces to airframe, usually
symmetric about c.g. to avoid applying pitch moment.
Often similar in principle to active controls.
structural placard Structurally significant airspeeds, eg
maximum gear-down or flap-extension IAS, displayed in
cockpit.
structural RAM RAM (2) material, often of hybrid types
such as CA overlying magnetic RAM, bearing some or all
of local skin structural loads.
structural section Cross-section not necessarily
unvarying, of structural materials or finished parts of high
fineness ratio, produced mainly by extrusion or rolling
between shaped dies but often machined to incorporate
tapers or discontinuities. Standard * appear in priced catalogues.
strut 1 Externally mounted structural member intended
to bear compressive loads, and usually of streamline
section.
2 Ambiguously, stub wing or pylon * attaching engine
pod to fuselage or wing (loads mainly tensile and bending).
3 Loosely, any major bracing member or portion of truss
even if load is tensile (suggest incorrect usage), thus a lift *
on braced highwing monoplane is a misnomer [it is a tie].
4 A structural member extending across the gas path of
a gas-turbine engine to transmit loads from a shaft bearing
without diverting the flow [see vane].
strutjet RBCC engine using multiple struts in air inlet.
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