- Celsius (temperature) or compass.
C of A - Certificate of Airworthiness issued by the CAA
indicating that an aircraft meets the Authority's airworthiness
standards. Cs of A are issued to individual aircraft, and also to
generic aircraft types (Type Certification in the USA) when the first
example of a type is registered. Cs of A on individual aircraft are
granted in several categories, e.g. Private, Public Transport, Aerial
Work etc. and much be renewed at intervals. Permits to Fly are
authorisations granted to aircraft such as homebuilts, vintage
aeroplanes, warbirds and some simple classic light aircraft which are
not required to meet the standards demanded for a full C of A, and are
accordingly restricted in the kinds of operation for which they may be
C of E - Certificate of Experience, valid for private pilot
licence holders for thirteen months, and renewed by flight test or
evidence of completing the minimum required flying experience in the
preceding thirteen month period. Also C of T, certificate of test.
C of G - centre of gravity. The point on an aircraft through
which the entire aircraft's weight may be assumed to act (i.e. around
which the aircraft, if suspended, would balance). C of G limits are
the most forward and rearward positions of the C of G permitted for
safe operation. An aircraft loaded outside its C of G limits can be
difficult or impossible to control.
C of P - centre of pressure, the point through which the total
effect of lift may be said to act on an aeroplane.
C/L - centre line (of a runway, for example).
c/s - call sign.
CAA - Civil Aviation Authority.
CAAFU - Civil Aviation Authority Flying Unit, based at Stansted
Airport, which performs such tasks as navaid checking and calibration
and also examines candidates for instrument ratings and commercial
CAD/CAM - computer aided design/manufacture.
CANP - Civil Aviation Notification Procedure. A voluntary
system whereby civil operators notify their intention to fly at low
level (at or below 1,000 feet agl, when crop spraying or powerline
inspecting for example), aimed at avoiding conflict with low flying
CAP - Civil Air Publication. Information booklets issued by the CAA, e.g. CAP 53 The Private Pilot Licence.
CAS - calibrated airspeed indicated airspeed corrected for air
density and compressibility.
casevac - casualty evacuation.
CAT - clear air turbulence. Also CATegory when referring to
certain instrument landing systems which require special aircraft
instrumentation, certification and pilot qualification beyond those
needed for standard instrument approaches (e.g. a CAT IIIC ILS permits
operation down to the surface of the runway without external visual
reference, true zero zero operation).
CAVOK - pronounced CAV okay (ceiling and visibility OK),
visibility at least ten kilometres, with no cloud below 5,000 feet,
with no Cbs, precipitation, thunderstorms, shallow fog or low drifting
CAVU - ceiling and visibility unlimited. Cloudless (or
scattered cloud) conditions with visibility in excess of ten
CDI - course deviation indicator. The vertical needle of a VOR
indicator which shows the aircraft's position relative to the selected
CDU - control display unit.
ceiling - height above ground or water of the base of the
lowest layer of cloud below 20,000 feet which covers more than half of
the sky. An aircraft's service ceiling is the density altitude (which
see) at which its maximum rate of climb is no greater than 100 feet
per minute. Its absolute ceiling is the highest altitude at which it
can maintain level flight.
CFI - chief flying instructor (certified flying instructor in
CH - compass heading.
Check 'A' - a thorough pre flight inspection the first of the
CHIRP - Confidential Human Factors Incident Reporting system,
whereby professional pilots and ATC staff may report in confidence
incidents arising from human errors for analysis by the RAF Institute
of Aviation Medicine at Farnborough.
CHT - cylinder head temperature (gauge). A device which, by
means of a probe(s) gives a cockpit readout of the temperature of one
or more of an aircraft engine's cylinder heads.
circuit - pattern around which aircraft fly when arriving at an
airfield, usually rectangular in UK but not necessarily elsewhere. The
circuit (pattern in USA) is aligned with the active runway and may be
either left or right handed. Dead side is the opposite side of the
circuit pattern in operation from which arriving aircraft join for
landing. See also final(s).
clean - flaps, slats and undercarriage retracted and on
military aircraft no external missliles etc.
clearance - authorization from air traffic control to proceed
as requested or instructed. Used for ground and air manoeuvring, thus
"cleared for take off", "cleared flight planned route", "cleared to
Clouds - commonly used abbreviations for cloud types:
AC = altocumulus
AS = altostratus
CB = cumulonimbus
CC = cirrocumulus
CI = cirrus
CS = cirrostratus
CU = cumulus
NS = nimbo stratus
SC = stratocumulus
ST = stratus
Com(m)(s) - communication(s)
CPL - Commercial Pilot's Licence
CR or C/R - counter rotating. Usually in general aviation
referring to twin engined aircraft with 'handed' engines whose
propellers turn in opposite directions to eliminate propeller torque
critical altitude - the highest density altitude at which it is
possible to maintain the maximum continuous rated power or manifold
pressure of an aero engine.
critical engine - the engine on a mult-engined aircraft whose
failure would most seriously effect performance or handling of the
aircraft, through asymmetric effects or loss of power to systems such
CRP - compulsory reporting point.
CRS course - the intended direction of flight in the horizontal
plane expressed in degrees of the compass.
CRT - cathode ray tube (like a television). Used in flight deck
displays of new EFIS, below. jets instead of conventional instruments.
See also generation airliners, business aircraft and military
CS - constant-speed (propeller). A variable pitch propeller
which maintains constant rpm by automatically changing blade angle.
Also CSU, constant speed unit.
CTA - Control Area. An area of controlled airspace extending
upwards from specified limit agl.
CTR - Control Zone. An area of controlled airspace extending
upwards from ground level to a specified upper limit.
CVR - cockpit voice recorder. A tape recorder installed on the
flight decks of commercial transport aircraft and helicopters and some
business aeroplanes to record crew conversation, RT transmissions and
cockpit background noises (e.g. trim wheel operation, flap motor
running) in case required for incident or accident investigation.
CW - carrier wave or continuous wave.
CWR - colour weather radar.
CZ - Control Zone (USA).
CZI - compressor zone inspection.