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point discharge
graph whose sole purpose is to assist location of small
features.
point discharge Gaseous electrical discharge from
surface of small radius (point, or tips of static wick) at
markedly different potential from surrounding; unlike
corona discharge, ** is silent and non-luminous.
point light Luminous signal without perceptible length
(ICAO).
point mass Simplifying equations of motion by
assuming aircraft has no dimensions, thus eliminating
torques and moments.
Point Mugu Location of Naval Missile Center and
Naval Missile Range (US).
point navaid Electronic navigation aid located at a single
site, e.g. NDB, VOR.
point of attachment Where balloon rigging cable joins
flying cable.
point of entry Where aircraft enters control zone.
point of equal time Same time to reach destination or
return to start.
point of interest Airfield, or point navaid.
point of inversion Height at which lapse rate at last
passes through zero; where temperature begins to fall.
point of no alternate Geographical position on track or
time at which fuel remaining becomes insufficient to reach
declared alternate.
point of no return Geographical position on track or
time at which fuel remaining becomes insufficient for
aircraft to return to starting point (DoD, NATO wording
‘to its own or some other associated base’).
point parallel Standard form of rendezvous for boomtype
tanker and large receiver, in which aircraft fly
reciprocal tracks to ARCP, tanker then turning 180° to
come up 3.5 miles ahead of receiver at roughly same
height, heading and speed.
point target 1 One requiring accurate placement of
conventional ordnance in order to neutralize or destroy it
(DoD).
2 With NW, one in which target radius is not greater
than one-fifth radius of damage.
point to point Linear motion of tool between NCinstructed
commands.
point vortex Section of straight-line vortex in 2-D
motion.
Poise Pointing and stabilization platform element
(USA, RPVs).
poise Non-SI unit of dynamic viscosity, defined as 1
dyn.s.m –2 = 0.1 Ns.m -–2 = 0.067197 lb.s/ft 2 .
Poiseuille equation Relates flow through tube (defined
as ‘long and thin’; elsewhere as ‘capillary’) to variables:
Q= π Pr 4 /8lµ where Q is volume per unit time (seconds),
P is pressure difference across ends of tube, r is radius, l is
length and µ is viscosity.
Poiseuille flow 1 Viscous laminar flow in circularsection
pipe.
2 Viscous laminar flow between close bounding planes.
Poisson’s equation In stressed material σ = (E/2n)–1
where σ is Poisson’s ratio, E is Young’s modulus and n is
modulus of rigidity.
Poisson’s ratio Ratio of lateral contraction (in absence
of local waisting) per unit breadth to longitudinal extension
per unit length for material stretched within elastic
limit, symbol υ or, less often, σ.
polar navigation
Poits Payload orientation and instrumented tracking
system.
poka yoke Japanese words meaning foolproof, ie
eliminating disruption caused by faulty work.
poke Propulsive thrust or power (colloq.), hence
‘pokier’, etc.
poke welding Similar to spot welding but using single
‘poked’ electrode, the other being clamped to any convenient
point on workpiece.
POL Petrol, or petroleum, oil and lubricant.
Pol, pol Polarity (but P in FFP).
Polar Precision over-the-horizon land attack rocket.
polar 1 Air mass supposedly originating near pole,
hence cold and usually dry: thus * Atlantic, * continental,
* front, * maritime.
2 Parameter plotted on polar co-ordinates.
3 Basic performance curve of sailplane in which sink
speed is plotted against EAS (units of two scales differ,
traditionally ft/s against kt but today m/s: km/h).
polar-cap absorption Radio blackout by HF absorption
in ionospheric storms.
polar continental Typically extremely cold, dry and
stable air mass; abb. Pc.
polar control Twist-and-steer flight control.
polar co-ordinates Those defining locations by means of
angle of a radius vector, measured relative to agreed direction,
and vector length; similar to rho-theta navigation.
polar diagram One giving values round 360° from a
point, eg noise, IR or radio emission, stress or
temperature.
polar distance Angular distance from celestial pole.
polar front That separating polar air mass from
contrasting mass.
polarimeter Instrument for determining degree of polarization
of EM radiation, esp. light.
polarimetry Particular meaning in aerospace is examination
of changes in polarization of radar returns from
different types of target surface.
polariscope Instrument for detecting polarized
radiation.
polarity 1 Of line segment, having both ends
distinguishable.
2 Hence, of physical system, having two contrasting
points, specif. oppositely marked terminals of electric cell
or plus/minus characteristics of ions.
polarization Many meanings but chiefly associated with
EM radiation in which * can be plane, elliptical or
circular. Plane * rotates all wave motion so that all E (electric)
vibrations take place in one plane (plane of vibration)
and all H (magnetic) vibration takes place at 90° to this
(plane of *).
polarization diversity Having ability to swtich from
plane-polarized to circular-polarized (radar).
polar maritime Air mass that is cold and, though
absolute humidity and dewpoint temperature low, relative
humidity is high; abb. Pm.
polar moment of inertia Moment of inertia of area about
axis perpendicular to its plane. Traditional symbol not I
but J.
polar navigation Navigation at high latitudes, distinguished
in bygone days on account of unreliability of
magnetic compass, possible electrical/radio inteference
and other problems such as rapid change of meridians and
map-projection difficulties.
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