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eserve parachute
reserve parachute Second, standby parachute usually
worn by professional parachutists and many others who
make frequent deliberate descents; 7.3 m/24 ft ** mandatory
for sport parachuting.
reserve power See specific excess power.
reserves Quantities of consumables, esp. fuel, planned to
be unconsumed when aircraft arrives at destination and
available for holding (stacking), go-arounds, diversions
and other contingencies.
reservoir Storage (not header) tank in fluid system, eg
hydraulics.
reset 1 To restore device, eg bistable gate, memory
address or fire-warning system, to original untriggered
state.
2 Process of recovering assets [notably helicopters]
from scene of conflict and refurbishing them for further
use (USA).
RESH Recent showers.
Reshabar Strong, dry squalls [S Kurdistan].
residence time 1 Time fuel droplet or gas particle
remains in either gas-turbine combustor or afterburner.
2 Time, usually expressed as a halftime (not to be
confused with half-life) radioactive material, eg fallout,
remains in atmosphere after NW detonation.
residual magnetism See remanence.
residual propulsive force Net propulsive force minus
total aircraft drag, F–D.
residuals 1 Any fluid left in spacecraft tanks after use.
2 Difference (plus/minus) between intended δ V
(velocity increment) for a burn and that achieved
(NASA).
residual stress That in structural component in absence
of applied load, due to heat treatment, fabrication or
other internal source.
residual thrust 1 That produced by jet engine (turbojet
or turbofan) at flight or ground-idle setting.
2 That produced by any other propulsion engine after
deliberate shutdown, or cutoff.
residual value Price paid for second-hand aircraft.
resilience Measure of energy which must be expended in
distorting material to elastic limit.
resin Vast profusion of natural and, increasingly,
synthetic materials used as adhesives, fillers, binders and
for insulation. Various types used in nearly all fibrereinforced
composites.
resin lamp Small lamp with filament bulb used not for
illumination but to indicate position, e.g. of wingtips of
aircraft in night formation.
resistance Opposition to flow of electric current, R =
V/I, unit ohm[s], symbol Ω.
resistance derivatives Quantities, generally dimensionless,
which express variation in forces and moments acting
on aircraft after upset. In general case there are 18 translatory
and 18 rotary.
resistance welding Using internal resistance of metal
workpiece to very large electric current to produce heating
which, under pressure, forms weld (see spot weld, seam
weld).
resistivity Specific resistance; electrical resistance of unit
length of material of unit cross-section. Convenient unit
ohm/cm 3 , though not strictly SI.
Resistojet Various patented (eg Avco, Marquardt)
space thrusters using liquid ammonia or other working
resonator
fluid, including biowastes, accelerated by solar-powered
electrothermal chamber with de Laval nozzle.
resistor Electrical device offering accurately specified
resistance.
reslams Repeated throttle slams for engine test.
RESM Radar electronic support measures.
RESN Recent snow.
resojet Usually means resonant pulsejet.
resolution 1 Measure of ability of optical system, radar,
video/TV or other EO system, photographic film or other
scene-reproducing method to reveal two closely spaced
objects as separate bodies; normally defined in terms of
angle at receiver subtended by two objects which can just
be distinguished as separate.
2 Ability of device, as in (1), to render barely
distinguishable pattern of black/white lines; expressed in
number of lines per mm which can just be distinguished
from flat grey tone. Both (1) and (2) also called resolving
power.
3 Measure of response of gyro to small change at input;
minimum change that will cause detectable change in
output for inputs greater than threshold, expressed as %
of half input range.
4 Separation of vector quantity into vertical/horizontal
components.
resolution advisory Verbal or display indication recommending
increased vertical separation relative to an
intruding aircraft.
resolver Subsystem in spacecraft INS which measures
changes of attitude, esp. rotation about longitudinal axis,
and informs guidance computers. In general a rotary digitiser
converting small angular movements to digital
signals.
resolving power 1 See resolution (1, 2).
2 Ability of radar set or camera to form distinguishable
images (ASCC); term unhelpful and indistinguishable in
practice from resolution (1, 2).
3 Reciprocal of unidirectional aerial beamwidth
measured in degrees (not synonymous with resolution [1],
which is affected by other factors).
resonance 1 Condition in which oscillating system such
as free wave or aircraft structure oscillates under forcing
input at natural frequency, such that any change in
frequency of impressed excitation causes decrease
in response.
2 Condition of AC circuit when, at given frequency,
inductive and capacitive reactances are equal.
3 In specific case of rotary-wing aircraft, particularly
helicopter, condition in which natural frequency of
landing gear corresponds with main-rotor rpm.
resonance test Structural exploration of natural
frequencies by excitation over slowly varying wide range
of frequencies.
resonant duct See resonant pulsejet.
resonant pulsejet Pulsejet in which intermittent
operation occurs at natural frequency of operating
air/fuel-burning duct system, without need for one-way
flap valves.
resonating cavity Closed hollow space of precise geometry
having electrically conductive walls in which
microwaves are generated when excited by EM field or
electron beam; examples are magnetron, klystron,
rhumbatron; also called resonant cavity.
resonator 1 See resonating cavity.
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