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centimetric radar
centimetric radar Radar operating on wavelengths
around 0.01 m, with frequencies 3–30 GHz.
centipoise See viscosity.
centistoke See viscosity.
CENTO, Cento Central Treaty Organization (1955–80,
Iran, Iraq, Pakistan, Turkey, UK, US).
central altitude reservation See CARF.
centralised fault display system Avionics system
accessing all on-board BITE systems to extract and
display data and initiate maintenance tests.
centralised servicing Establishment of one unit and site
for all routine maintenance on station, breaking previous
intimate relationship between crew chief and each aircraft
(RAF).
central warning panel See CWP (I).
centrebody Streamlined body in centre of circular, semicircular
or quasi-circular supersonic intake (inlet) to cause
inclined shock.
centre controls To move primary flight controls from
deflected to neutral position.
centre engine Engine on centreline of multi-engined
aircraft.
centreline 1 Principal longitudinal axis; usually also axis
of symmetry (eg of aircraft, missile, runway).
2 In aerofoil section, line joining leading and trailing
edges and everywhere equidistant from upper and lower
surfaces, all measures being normal to line itself.
centreline aircraft See centreline engine[s].
centreline camber Ratio of maximum distance between
chord and centreline (2) to chord.
centreline closure Compressor, or [more often] turbineblade
rub caused by slight radial displacement.
centreline engine[s] Any engine on longitudinal centreline
of multi-engine aircraft [engines hung on side of
fuselage or in wing roots are excluded]. The pilot does not
need a multi-engine rating.
centreline gear Main landing gear on aircraft centreline.
centreline lighting On runway, flush lights at 50 ft (15 m)
intervals terminating 75 ft (23 m) from each threshold.
centreline noise plot Plot of aircraft noise, usually
EPNdB, along runway centreline extended (usually 6 st
miles, 9.6 km) in each direction covering approach and
climb-out.
centreline tank Centre tank 1 [not 2].
centre of area See centroid.
centre of buoyancy Point through which upthrust of
displaced fluid acts; e.g. in case of aerostats and marine
aircraft afloat.
centre of burst Mean point of impact.
centre of dynamic lift In aerostat, point on centreline
through which lift force due to motion through atmosphere
acts.
centre of gravity, c.g. Point through which resultant
force of gravity acts, irrespective of orientation; in
uniform gravitational field, centre of mass. For twodimensional
forms, centroid.
centre of gravity limits In nearly all aircraft, esp. aerodynes,
published fore and aft limits for safe c.g. position;
in case of aeroplanes expressed as percentages of MAC.
centre of gravity margin H n , distance along aircraft
major axis from c.g. to neutral point, expressed as
% SMC.
centre of gravity travel Fore and aft wander of c.g. in
centrifugal compressor
course of flight due to consumption of fuel, release of
loads, etc.
centre of gross lift In aerostat, usually centre of buoyancy.
centre of gyration For solid rotating about axis, point at
which all mass could be concentrated without changing
moment of inertia about same axis.
centre of lift Resultant of all centres of pressure on a
wing or other body.
centre of mass Point through which all mass of solid
body could act without changing dynamics in translational
motion; loosely, but not always correctly, called
c.g. Alternative title, centre of inertia.
centre of pressure, c.p. On aerofoil, point at which line
of action of resultant aerodynamic force intersects chord.
Almost same as aerodynamic centre, but latter need not
lie on chord. In general, c.p. is resultant of all aerodynamic
forces on surface of body.
centre of pressure coefficient Ratio of distance of c.p.
from leading edge to chord.
centre of pressure moment Product of resultant force on
wing (or section) and distance from c.p. to leading edge
(or leading edge produced at aircraft centreline).
Inapplicable to very slender wings.
centre of pressure moment coefficient As above but
divided by dynamic pressure; not same as coefficient of
moment.
centre of pressure travel 1 Linear distance through
which c.p. travels along chord over extreme negative to
positive operating range of angles of attack, ignoring
compressibility in subsonic flow.
2 Linear distance through which c.p. travels along
chord over complete aircraft operating range of Mach
numbers (supersonic aircraft only).
centre of thrust Thrust axis, for one or multiple engines.
centre of twist The axis about which a solid body rotates
when under an applied torque.
centre punch Hand tool for making accurate conical
depressions.
centre section In most winged aircraft, centre portion of
wing extending symmetrically through or across fuselage
and carrying left and right wings on its tips. Certain
aircraft have wing in one piece, or in left and right halves
joined at centreline; such have no **, though some authorities
suggest it is then wing inboard of main landing gear.
centre tank 1 Most commonly, a fuel tank inside the
fuselage in a system havng additional tanks in the wings.
2 A tank inside the inboard part of each wing, usually
structurally part of the single main inter-spar box, and
separated from the main tank by a rib.
centrifugal breather Centrifuge filter for removing oil
from air vented overboard from interior of engine, often
after passage through porous segments.
centrifugal clearance Radial clearance between rotating
mass and surrounding fixed structure at peak rotating
speed.
centrifugal clutch Freewheels at low speed, but takes up
drive as speed is increased. At full power slip tends
towards zero. Main purpose is to prevent excessive load
on gearteeth.
centrifugal compressor Rotary compressor in form of
disc carrying radial vanes to accelerate working fluid radially
outward to leave periphery at very high speed, this
being converted to pressure energy in fixed diffuser.
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