CARC CPL Theory key terms

A set of rules allowing a pilot to operate an aircraft by reference to the ground and horizon, subject to specified minimum visibility and distance-from-cloud requirements.

Weather conditions below the minimum visibility or cloud-clearance values for VFR, requiring the flight to be conducted under instrument flight rules or not at all.

Rules governing flight by reference to instruments, with prescribed separation, equipment and pilot qualification requirements, permitting operation in cloud and low visibility.

A clearance allowing a VFR flight inside controlled airspace when weather is below normal VFR minima, provided the aircraft remains clear of cloud and in sight of the surface.

Controlled airspace of defined dimensions extending from the surface upward around an aerodrome, within which IFR and special VFR flights receive air traffic control service.

An authorisation issued by air traffic control for an aircraft to proceed under specified conditions, which the pilot must either comply with or request to have amended.

The pilot's repetition back to air traffic control of safety-related clearance elements, confirming the message was received and understood correctly before it is acted upon.

The four-digit code set in the aircraft transponder so that air traffic control radar displays identify and track the flight correctly.

An airborne radio unit that replies to ground radar interrogations, transmitting the aircraft's assigned code and, in Mode S, identity and pressure altitude information.

A document confirming that an individual aircraft conforms to its approved type design and is maintained in a condition fit for safe flight.

A mandatory instruction issued by the state of design requiring inspection, modification or limitation of an aircraft or component to correct an unsafe condition.

A certification, signed after completed maintenance, stating that the work has been carried out to approved standards and the aircraft or component is serviceable.

The point at which the aircraft's total weight is considered to act; it must remain within a specified forward and aft range for safe control and performance.

The horizontal distance from the datum to a point where a weight acts; multiplying weight by arm gives the moment used in centre-of-gravity calculations.

A document showing the distribution of traffic load, zero-fuel and take-off mass, and the resulting centre-of-gravity position, signed before departure.

The highest mass at which the aircraft is certified for the start of the take-off run, accounting for structure, performance and climb requirements.

The pressure altitude corrected for non-standard temperature; higher density altitude reduces engine power, propeller thrust and wing lift, lengthening take-off and climb.

The altitude indicated on an altimeter set to the standard pressure of 1013.2 hPa, used as the basis for performance and flight-level calculations.

The use of a pressure altimeter and the correct pressure setting to determine and maintain aircraft height or flight level above a reference surface.

The altitude in the vicinity of an aerodrome at and above which pilots change the altimeter setting from local pressure to standard pressure and fly by flight level.

The angle between the wing chord line and the relative airflow; lift increases with it until the critical angle, beyond which the wing stalls.

A loss of lift occurring when the wing exceeds its critical angle of attack, producing buffet and a sink that is recovered by reducing the angle of attack.

The ratio of total lift to the aircraft's weight; it increases in turns and manoeuvres and raises the speed at which the wing will stall.

A condition in which body tissues receive insufficient oxygen, causing impaired judgement, confusion and eventual loss of consciousness, with insidious onset at altitude.

Abnormally rapid or deep breathing that lowers blood carbon dioxide, producing dizziness, tingling and faintness that can be mistaken for hypoxia.

A false perception of the aircraft's attitude or motion arising when the balance organs give misleading signals in the absence of reliable visual references.

A false sensation of pitching up during acceleration, or pitching down during deceleration, caused by linear acceleration stimulating the inner ear.

The period after exposure to insufficient oxygen during which a person can still perform useful, deliberate actions before incapacitation occurs.

The altimeter pressure setting that makes the instrument indicate altitude above mean sea level at the aerodrome when the aircraft is on the ground.

The altimeter pressure setting that makes the instrument read height above a specified reference point, usually the aerodrome elevation.

The standard pressure setting of 1013.2 hPa used above the transition altitude, so that the altimeter displays flight levels rather than altitude.

A layer in which temperature increases with height, suppressing vertical mixing, trapping haze or low cloud beneath it and giving often smooth, stable air.

The temperature to which air must be cooled at constant pressure for it to become saturated; a small gap between temperature and dew point favours cloud and fog.

A line on a weather chart joining places of equal sea-level pressure; their spacing indicates the strength of the pressure gradient and hence surface wind speed.

The amount of water vapour present in the air expressed as a percentage of the maximum the air could hold at that temperature.

The angular difference at a given place between true north and magnetic north, applied when converting between true and magnetic directions on charts.

The error of a magnetic compass caused by the aircraft's own magnetic fields, tabulated on a compass correction card and applied to give compass heading.

The direction in which the aircraft's longitudinal axis points, measured clockwise from true north, before variation and deviation corrections are applied.

A ground beacon transmitting signals from which an aircraft receiver derives its magnetic bearing from the station, giving a position line for navigation.

A magnetic bearing measured from a VOR station outwards, quoted as the bearing from the station to the aircraft, such as radial 270.

A ground transmitter radiating an unmodulated carrier that an automatic direction finder uses to display the relative bearing to the station.

A standard set of spoken code words, such as Alpha, Bravo and Charlie, used to spell out letters unambiguously over the radio.

The international radiotelephony distress call, spoken three times, used when an aircraft is threatened by grave and imminent danger and requires immediate assistance.

The international radiotelephony urgency call, spoken three times, used for a condition concerning safety that does not require immediate distress assistance.