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water level
water level Generalized term in lofting and aerospace
construction generally (except vehicles whose major axis
is vertical, eg most space launchers) to denote measures in
the vertical plane; thus ** 193 = 193 mm above aircraft
reference datum for measures in vertical plane, which may
be longitudinal axis OX or some other essentially horizontal
reference; abb. WL. Note: in US unit is often still
inches.
waterline 1 Intersection of body exterior profile and a
horizontal plane; often used as synonymous with water
level, thus WL 0 is lowest point of body and all subsequent
slicing planes are parallel to prime longitudinal axis or
other horizontal reference. Thus * view, * plot (all waterlines
drawn on common axis of symmetry).
2 Any horizontal reference other than local Earth
surface used in aircraft attitude instrument or HUD.
waterloop Inadvertent turn by marine aircraft on water,
eg after dipping wingtip float at high speed (full ** rare
because usually aircraft rolls in opposite direction
through centripetal force).
watermarking Sending spread-spectrum digital signal
during first 900 ms of transmission to provide secure identification
of sender.
water/methanol See water injection.
water recovery Recovery of usable water from propulsion
exhaust, esp. aboard airship for use as ballast.
water resistance Drag caused by water to aircraft
moving through it, made up of skin friction and wavemaking.
water rudder Small surface usually hinged on centreline
of marine aircraft to sternpost or rearstep heel; used for
directional control on water.
waterspout Visible water-filled tornado over sea.
water suit Anti-g suit in which interlining is filled with
water which automatically provides approx. required
hydrostatic pressures under large normal accelerations.
water tunnel Similar to wind tunnel but using water as
working fluid for large R at low V.
water twister Rotary liquid-turbine device which
absorbs energy in MAG arrested landings.
WATOG, Watog World Airlines Technical Operations
Glossary.
WATRS West Atlantic route system.
WATS Wide-area tracking system.
watt SI unit of power (not only electrical power), W =
J/s. Conversion factors: hp 745.7 exactly, CV 735.499,
Btu/min 17.5725, in each case to convert to * from unit
stated.
watt-hour SI unit of energy = 3,600 J.
wattless power Reactive power VAR; also called wattless
component.
Wave, WAVE 1 Warfighter alliance in a virtual environment
(NATO0.
2 Wide-area voice environment.
wattmeter Instrument for measuring electrical power.
wave 1 Disturbance propagated in medium such that at
any point displacement = f (time) and at any time
displacement of point = f(position); any time-varying
quantity that is also an f(position). This definition falls
down for light and other EM radiation, which appears not
to need a ‘medium’ for propagation (f = function of).
2 Formation of assault vehicles (land, sea or air) timed
to hit hostile territory at about same time.
wave angle Angle between upstream free-stream direc-
wave soaring
tion and an oblique shock created by a real [large source]
supersonic body, symbol α.
waveband Particular portion of EM spectrum in
telecommunications frequency region assigned by
national authority for specific purpose.
wave cloud Formed at crest of a lee wave.
wave crest Peak of waveform.
wave disturbance Discontinuity or distortion along a
met. front.
wave drag Additional increment of aerodynamic drag
caused by shockwave formation, made up of distribution
of volume along length (longitudinal axis) and drag due
to lift; symbol for coefficient of ** C DW .
waveform Shape of a repetitive (eg sinusoidal) wave
when plotted as amplitude against time-base or when
displayed on CRT.
waveform generator Converts d.c. or raw a.c. into any
desired waveform output, with any frequency, amplitude
(both time-varying if required) or other characteristic, eg
for testing airborne electronic systems.
wave front 1 Leading edge of shockwave group, or of
blast wave from explosion.
2 In a repetitive wave, a surface formed by points which
all have the same phase at a given time.
waveguide Conductor for EM radiation in reverse sense
to normal conductor in that radiation travels through
insulator (usually atmosphere) surrounded by metal
walls, usually rectangular cross-section, along which
waves propagate by multiple internal reflection. Rarer
form is dielectric cylinder along whose outer surface EM
radiation propagates.
waveguide modes See propagation modes.
waveguide mode suppressor Filter matching particular
waveguide cross-section designed to suppress undesirable
propagation modes.
wavelength Distance between successive wave crests;
symbol λ = v/f where v is velocity of EM radiation (usually
close to speed of light) and f is frequency.
wavelet Small shockwave, usually present in large
numbers in boundary layers and around surface of supersonic
body. Sometimes called Mach wave or Mach *.
wave lift Lift on lee side of ridge or mountains.
wavemaking resistance Drag of taxiing marine aircraft
caused by gross displacement of water in waves; reaches
maximum at about 20–30% of unstick speed.
wave motion Oscillatory motion of particle(s) caused by
passage of wave(s), usually involving little or no net translation,
ie particle resumes near-original position after
wave has passed. Direction of ** varies with transverse
waves (eg EM radiation), longitudinal waves (sound) or
other forms, eg surface (water/air interface) waves.
wave number Reciprocal of wavelength 1/λ or (alternatively)
2π/λ.
waveoff, wave-off Any landing prevented, for whatever
reason, by a command from the ground terminal or
carrier DLCO.
wave period Elapsed time between successive crests, 1/f,
where f = frequency.
waverider Hypersonic aircraft designed to use shockwaves
to increase L/D ratio.
Waves Women Accepted for Voluntary Emergency
Service (USN, from 1942).
wave soaring Using wave lift.
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