CAAB ATPL Theory key terms

The 1944 international treaty that set the basic framework for civil aviation, creating ICAO and establishing principles such as national sovereignty over airspace and mutual recognition of certificates and licences.

One of the numbered documents attached to the Chicago Convention containing the international standards and recommended practices for a specific subject, such as personnel licensing, aircraft operations or meteorology.

A document issued for an individual aircraft confirming that it meets the applicable airworthiness requirements and remains safe to operate within its specified limitations and approved conditions.

An authorisation granted by a national aviation authority allowing an operator to carry passengers or cargo for commercial air transport, specifying the aircraft types and kinds of operation permitted.

The set of probes, ports and pipework that supplies ram air pressure and static pressure to the airspeed indicator, altimeter and vertical speed indicator, and often to air data computers.

A small engine, usually mounted in the tail, that supplies electrical and pneumatic power on the ground and can provide bleed air for engine starting or standby power in flight.

A propeller whose blade angle is adjusted automatically by a governor so that it turns at a selected constant RPM as engine power, airspeed or altitude changes.

A pressure vessel containing hydraulic fluid and compressed gas that stores energy, smooths pressure fluctuations and provides a limited reserve of pressure for emergency operation of systems.

The take-off decision speed. Above it the take-off must be continued after an engine failure; below it the take-off can be abandoned and the aircraft stopped within the runway distance available.

The shortest runway length for which the accelerate-stop distance equals the take-off distance required after an engine failure, giving the lowest practical V1 for a given mass.

Pressure altitude corrected for the deviation of temperature from the standard atmosphere. High density altitude reduces engine power, propeller thrust and lift, lengthening take-off and reducing climb performance.

The mass of the aircraft together with its payload and crew but without usable fuel. It must stay below a maximum limit that protects the structure from excessive loads.

A condition in which body tissues receive insufficient oxygen. It degrades judgement, coordination and vision early on, and is hazardous because the affected person often fails to notice the symptoms.

A situation in which a pilot loses awareness of the aircraft's true attitude or motion because of misleading sensory inputs, most often in poor visual conditions without reliable instrument reference.

A false sensation of pitching up during rapid acceleration, or pitching down during deceleration, caused by the otolith organs responding to linear acceleration instead of true vertical.

Training and practice in using all available resources, including people, equipment and information, to improve communication, leadership, decision-making and teamwork in the cockpit and with other agencies.

The altimeter setting that makes the altimeter indicate elevation above mean sea level when the aircraft is on the ground at the aerodrome, giving approximate altitude in flight.

The boundary between the troposphere and the stratosphere where the temperature lapse rate becomes almost zero. Its height varies with latitude and season and affects weather and aircraft performance.

A narrow, fast-moving band of wind near the tropopause, typically thousands of kilometres long and a few kilometres deep, linked to strong temperature gradients and clear air turbulence.

A small, intense downdraught that produces a damaging outflow of wind at the surface. An aircraft crossing it meets a headwind, then a downdraught, then a tailwind, with severe performance loss.

The largest circle that can be drawn on the surface of a sphere, formed by a plane passing through its centre. Its arc gives the shortest route between two points on the Earth.

The angle between true north and magnetic north at a particular place, expressed as east or west, used to convert between true and magnetic courses, headings and bearings.

A magnetic bearing from a VOR station, displayed to the pilot as a line of position. Tracking a selected radial means keeping the aircraft on that bearing to or from the station.

A navigation method in which the aircraft's position is calculated from a known starting point using heading, true airspeed, wind and elapsed time, without direct reference to external position fixes.

A document approved for an operator listing items of equipment that may be inoperative while the aircraft is still allowed to fly, subject to stated conditions, limitations and repair intervals.

A notice distributed to aviation personnel giving information about the establishment, condition or change of any facility, service or procedure that is important to flight operations.

The altitude, published for an aerodrome or area, above which pilots set the standard pressure setting and express their height as flight levels instead of altitudes.

An approach that satisfies defined criteria such as correct speed, configuration, descent rate and track by a specified height, so that a normal landing or a safe go-around can be made.

The angle between the aerofoil chord line and the relative airflow. Lift rises as angle of attack increases until the critical angle is reached, beyond which the wing stalls.

Drag produced as a by-product of lift, caused by spanwise flow that forms wingtip vortices. It increases with lift coefficient and decreases as speed increases.

The ratio of total lift to aircraft weight, usually expressed in g. Higher values raise stall speed and structural loads, particularly in turns, gusts and abrupt manoeuvres.

The free-stream Mach number at which the airflow somewhere on the aircraft first reaches the local speed of sound, creating shock waves and the start of compressibility effects.

The procedure in which a pilot repeats a clearance or instruction from air traffic control back to the controller, confirming that it has been received and understood correctly.

The international radiotelephony distress signal, spoken three times at the start of a call, used when an aircraft is in grave and imminent danger and needs immediate assistance.

To enter a four-digit code into the aircraft transponder so that secondary surveillance radar can identify the aircraft and display specific states such as emergency or radio failure.

Selective calling. A system in which a ground station transmits a coded tone that triggers a chime in one specific aircraft, so that crews need not monitor a long-range frequency continuously.