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angels
angels 1 Historic military R/T code word for altitude in
thousands of feet; thus, ‘angels two-three’ = 23,000 ft.
2 Distinct, coherent and often strong (40 dB above
background) radar echoes apparently coming from clear
sky. Probable cause strong pressure, temperature or
humidity gradient in lower atmosphere giving even
sharper gradient in refractive index.
Angit Aircraft next-generation identification
transponder.
angled deck Aircraft-carrier deck inclined obliquely
from port (left) bow to starboard (right) stern to provide
greater deck space, greater catapult capacity and unobstructed
flight path further from island than with axial
deck, with safe parking area towards bow.
angle of ... In general, see under operative word.
angle of attack indicator Instrument served by ***
sensing system.
angle of attack sensing system Incorporated in aircraft,
esp. aeroplane, to trigger stall-warning, stall-protection
system or other desired output, and possibly serve an indicator.
Sensing unit (SU) comprises freely pivoted vane or
series of pitot tubes set at different angles of incidence and
each connected to different supply pipe to give dP output.
SU on wing leading edge, to sense movement of stagnation
point, or on side of fuselage, repeated on opposite
side to eliminate error due to sideslip. SU anti-iced and
must allow for changes in aircraft configuration.
angle of depression Acute angle between axis of oblique
camera and horizontal.
angle of downwash Downwash (I).
angle off Acute angle between own-fighter sightline and
longitudinal axis of target aircraft.
angle of incidence indicator Instrument giving continuous
reading of angle of foreplane, horizontal tail
(especially tailplane where not primary pitch control) or
wing, where incidence variable.
angle of view Angle subtended at perspective centre of
camera lens by two opposite corners of format.
Anglico Air/naval gunfire liaison company (USMC).
ANGR Air navigation (general) regulation[s] (UK).
ANGRC Air National Guard Readiness Center.
ANGSA Air National Guard support aircraft.
Angstro˚ m Unit Å or AU, unit of length equal to 10 –10 m,
formerly used to express wavelengths of light; nearest SI
is nanometre; 1 nm = 10 Å.
angular acceleration Time rate of angular velocity of
body rotating about axis which need not pass through it;
unit rad/s 2 .
angular displacement 1 Angular difference between two
directions or axes, esp. between reference axis of hinged
or pivoted body and same axis in neutral or previous
position.
2 In magneto, angular difference between neutral
position of rotor pole and later position giving highestenergy
spark (colloq., E-gap).
angular distance 1 Angular displacement.
2 Smaller arc of great circle joining two points
expressed in angular measure.
3 In all sine-wave phenomena (radio, radar,
astronomy, etc), number of waves of specified frequency
between two points (numerically multiplied by 360 or 2π
depending on whether unit is degree or radian).
angular measure 1 SI unit of plane angle is radian (rad),
angle subtended by arc equal in length to radius of circle
on which arc centred. Thus one revolution = 2π rad, and
1 rad = 57.296°. Degree (°) defined as 1/360th part of one
revolution, itself subdivided into 60 minutes (') each
subdivided into 60 seconds ("); pedantically distinguished
from units of time by calling them arc-minutes and arcseconds.
Thus 1 rad = 57° 17' 45". For small displacements
milliradian (mrad) to be used; roughly 3' 26¼"; thus 1' =
0.2909 mrad.
angular momentum For rigid body of significant mass
(not elementary particle), product of angular velocity and
moment of inertia; or, if axis of rotation at some distance
from it (as in axial turbine blade), mass, instantaneous
linear velocity and radial distance of CG from axis. Thus,
L= Iω = mvr.
angular resolution Angular distance between LOS from
radar, human eye or other “seeing” system to target and
LOS from same system to second target which system just
distinguishes as separate object; usually only a few mrad,
esp. if targets are pinpoints of light against dark background.
angular speed 1 Loosely, angular velocity.
2 Rate of change of target bearing, esp. as seen on PPI.
angular velocity Symbol ω, time rate of angular displacement
of body rotating about axis which need not pass
through it. Preferred measure is rad s –1 or mrad s –1 ; in
traditional engineering most common is rpm. Multiplied
by radius gives tip speed, or peripheral speed.
anharmonic Not harmonic, irregular.
anhedral 1 Negative dihedral, smaller angle between
reference plane defining wing (such as lower surface or
locus of AMCs) which slopes downward from root to tip,
and horizontal plane through root. In early aircraft dihedral
considered desirable as means to natural stability,
esp. in roll; in some, and many modern gliders, wing
flexure converts static * into dihedral under 1 g in flight.
Tendency to design modern wing with * to counter excesive
roll response to sideslip or side gusts, esp. in
high-wing or supersonic aircraft. VG aeroplane angle may
be varied with sweep. In the new century the term appears
to be dying, replaced by dihedral with a minus sign
2 Some authorities define as ‘absence of dihedral’ (from
Greek root of prefix an = not), and suggest “cathedral”
for downward-sloping wing.
ANIAF Associazione Nazionale Imprese Aerofotogrammetriche
(I).
Anics Alaskan NAS(2) interfacility communications
system.
ANIE Associazione Nazionale Industrie Elettrotechniche
ed Elettroniche (I).
aniline Phenylamine, aminobenzene, C 6 H 5 NH 2 , colourless,
odorous amine, MPt –6°C (thus, normally liquid),
BPt 184°C, turns gradually brown on exposure to air,
reacts violently with RFNA or other strong nitric acids
with which often used as rocket propellant.
anion Negative charged ion or radical, travels towards
anode in electrolytic cell.
anisotropic Exhibiting different physical properties
along different axes, esp. different optical properties or, in
structural material, different mechanical properties, esp.
tensile strength and stiffness.
ANIU Aircraft network interface unit.
ANK Automatic navigation kit.
ANL 1 Auto noise limiter (communications).
2 Automatic noise levelling.
ANL
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