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centrally above value, thus if a is acceleration along flightpath
ȧ is rate of change of acceleration, or acceleration*.
rated Qualified for specific flight duty, especially to fly
particular aircraft type.
rated altitude That at which piston engine gives
maximum power, for supercharged engine usually at
height considerably above S/L; lowest altitude at which
full throttle is permissible (or, usually, obtainable) or
maximum boost pressure can be maintained at maximum
rpm in level flight.
rated coverage Area within which strength of NDB
vertical field of ground wave exceeds minimum value
specified for geographical area where situated.
rated power Any of several specified limits to gasturbine
power, eg take-off, 2½ min. contingency,
maximum continuous.
rate gyro Gyro whose indication gives a rate term, rate
of change of attitude; single degree-of-freedom gyro with
primarily elastic restraint of spin axis about output axis.
rate integrating gyro Single-degree-of-freedom gyro
whose output axis is linked to spin axis by viscous
restraint so that angular displacement is proportional to
integral of angular rate of change of attitude. Abb. Rig
(not recommended).
rate of climb Rate of gain of height, vertical component
of airspeed of aircraft (normally aerodyne) established in
climbing flight at quasi-constant airspeed (ie not in zoom
trading speed for height). For helicopter, two values;
maximum *** and maximum vertical ***.
rate-of-climb indicator See VSI.
rate of temperature-rise indicator Fire-warning system;
does not respond to temperature but to positive rate of
change.
rate of turn Rate of change of heading, proportional to
bank angle θ; R (turn radius), for constant speed, is
exactly proportional to tan θ. See turn rate.
rates of exchange Tradeoff multipliers, eg numerical
value linking takeoff field length or MTOW for
unchanged takeoff field length per °C change in ambient
temperature.
Rate 1 turn Sustained 3°s –1 , = 180° min –1 . See turn rate.
rate structure Comprehensive and in general internationally
agreed prices for air carriage of unit mass of all
commodities.
RATG Ram-air turbine generator.
rating 1 Authorized operating regimes, with limiting
numerical values, for engine or other functional device or
system. For gas-turbine engine can include takeoff,
maximum climb, maximum cruise, OEI contingency, etc;
for piston engine can include METO, maximum weak
mixture, etc.
2 Anti-knock value of piston-engine fuel.
3 Endorsements, additional qualifications, privileges
and limitations added to airmen certificate (US) or pilot’s
licence (UK), eg night *, IMC *, seaplane *, multiengine
*, instrument * and flying instructor *. See Type.
rating spring Spring, usually with linear output, whose
change in length is accurately proportional to applied
force.
ratio changer Device for varying the response of a flightcontrol
surface, especially rudder, to input demand,
usually in proportion to q (dynamic pressure).
ratio of specific heats For a gas, ratio of specific heat at
RB
constant pressure divided by specific heat at constant
volume; for air γ = C p /C v = 1.401.
Rato, RATO Rocket-assisted takeoff; G or g adds gear,
meaning not landing gear but equipment.
Ratrace Radar transmitter waveguide shape facilitating
use of common aerial for transmitting and receiving.
RATS, Rats 1 Rapid area transportation support
(USAF).
2 Rescue advanced-tactics school.
3 Roving aerodynamic test system.
Ratscat Radar-target scatter; more fully, radar-target
test scatter facility.
RATT Radio teletype.
Rattlr, RATTLR Revolutionary approach to time-critical
long range; S adds strike (USN).
RAU Radio access unit.
RAV Robotic air vehicle [also called Rave].
Rave 1 Rapidly adjustable variable exhaust.
2 Reconfigurable advanced visualization environment,
virtual-reality display.
raven Electronic-warfare officer, specialist flight crew
member (US).
RA/VSI Resolution advisory/vertical speed indicator.
raw Versatile word meaning ready for next stage of
processing; thus * AC is ready for precise frequency
control before being supplied to avionics; * data can be of
many forms (instrument readings, reconnaissance photos,
tabular statistics); and * material is in fact anything but *
yet still unmanufactured into product.
rawin Wind velocity at different heights computed by
radar tracking of balloon (usually with transponder).
rawinsonde See radar-sonde.
RAWS 1 Radar altitude warning system.
2 Radar attack (and) warning system.
3 Remote-area weather station.
4 Role-adaptable weapon system.
Rayleigh atmosphere Ideal atmosphere devoid of all
particles larger than about 0.1 wavelength of incident
radiation.
Rayleigh flow First (1876) theory since Newton for lift
of inclined-plane wing; streamlines travel direct to
surface, where they are brought to rest, losing all relative
energy.
Rayleigh formula Another Rayleigh equation gives loss
of pitot pressure caused by presence of normal shock, in
terms only of Mach numbers, pressures and γ (ratio of
specific heats of gas).
Rayleigh limit One-quarter of an EM wave, maximum
difference in optical path.
Rayleigh number Non-dimensional ratio Nra =
gd
––––––—–––
3 ∝ (θ 2 θ 1 ) where g is acceleration due to gravity, d is
vk
vertical separation of two horizontal planes in fluid
system (eg atmosphere), θ 2 - θ 1 is temperature difference
across planes, ∝ is coefficient of thermal expansion, v is
coefficient of kinetic viscosity and k is thermal conductivity.
Rayleigh scattering Normal scattering of radiation by
particles whose ruling size is 0.1 or less that of radiant
wavelength; explains why sky is blue above and
red/orange at sunset.
Rayleigh wave 2-D barotropic fluid disturbance or wave
propagated along free solid surface.
RB 1 Rescue boat (ICAO).
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