GCAA Ghana ATPL Theory key terms

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

A document issued by the state of registry confirming that the aircraft conforms to an approved type design and is considered safe to operate within specified conditions and limitations.

The set of processes, inspections, and maintenance tasks that keep an aircraft in a condition compliant with its type design and airworthiness requirements throughout its operational life.

A certification signed by authorised maintenance personnel confirming that specified maintenance has been completed and the aircraft or component is fit for return to service.

An operator-approved document listing items of equipment that may be inoperative while the aircraft remains airworthy, subject to specific conditions, limitations, and operating procedures.

A document approved with the aircraft type design identifying external missing items, such as fairings, that are permitted with associated performance penalties and conditions.

A four-digit octal number selected on the transponder that identifies the aircraft to air traffic control secondary surveillance radar, often assigned by ATC for identification and separation.

A radar system in which ground interrogators transmit pulses that trigger replies from an aircraft transponder, providing identity, and with Mode C or S, pressure altitude information.

A transponder reply mode that includes the aircraft's pressure altitude, encoded from a static-source-derived altitude signal, allowing ATC to display and monitor altitude.

The aircraft system of pressure sensors and lines that supplies total pressure from the pitot tube and static pressure from static ports to instruments measuring airspeed, altitude, and vertical speed.

The pressure setting that, when entered on the altimeter subscale, causes the instrument to indicate aerodrome elevation when the aircraft is on the ground at that aerodrome.

The altitude at or below which the aircraft's altitude is controlled by reference to the altimeter set to local QNH, and above which flight levels referenced to standard pressure are used.

A surface of constant atmospheric pressure related to a datum of 1013.25 hPa and shown in hundreds of feet, used above the transition altitude for vertical position referencing.

The ratio of an aircraft's true airspeed to the local speed of sound, used to describe compressibility effects and to set limiting speeds at high altitude.

The free-stream Mach number at which airflow somewhere on the airframe first reaches the local speed of sound, producing shock waves and the onset of drag rise.

A condition at high Mach number where shock-induced separation of airflow over a wing causes loss of lift and buffet, often accompanied by pitch changes and reduced control effectiveness.

The angle between the wing chord line and the relative airflow, determining lift coefficient and, beyond the critical angle, the onset of aerodynamic stall.

The ratio of lift produced to the aircraft's weight, expressed in g units, which increases in turns and manoeuvres and raises the speed at which the wing stalls.

A loss of lift caused by airflow separation when the wing exceeds its critical angle of attack, which can occur at any speed, attitude, or weight.

The point through which the total weight of the aircraft acts, whose position must remain within specified forward and aft limits for safe control and performance.

The mass of an aircraft including structure, powerplant, equipment, unusable fuel, and all operating fluids, but excluding crew, passengers, payload, and usable fuel.

The mass of the aircraft including all contents except usable fuel, obtained by adding traffic load and crew to the basic empty mass.

The horizontal distance from the reference datum to the point where a mass acts, used with that mass to calculate its moment for balance and centre of gravity determination.

The length of the take-off run available plus any clearway provided, defining the maximum distance declared for the take-off phase at an aerodrome.

The runway length at which the accelerate-stop distance equals the take-off distance to 35 ft, giving the shortest field allowing both a rejected and continued take-off.

The maximum speed by which the take-off decision must be made; below it a rejected take-off should stop within the runway, above it a continued take-off is normally safer.

The take-off safety speed to be achieved by the end of the take-off distance, giving the minimum climb gradient required with one engine inoperative.

The pressure altitude corrected for non-standard temperature, representing the altitude at which the aircraft would perform as if in standard atmosphere conditions.

The altitude indicated when the altimeter subscale is set to 1013.25 hPa, used as a reference for performance charts and flight level allocation.

A change in wind speed or direction over a short distance, often associated with fronts, thunderstorms, or inversions, which can cause abrupt airspeed and lift changes.

A small, intense downdraught that spreads out on reaching the ground, producing a strong headwind-to-tailwind reversal near the surface and severe low-level wind shear.

Unstable atmospheric conditions producing vertical motion, cumuliform cloud, turbulence, icing, hail, and thunderstorms, often triggered by heating or frontal lifting.

The altimeter pressure setting that makes the instrument read zero when the aircraft is on the ground at the aerodrome reference point, useful for traffic pattern height keeping.

Exhaust gas temperature, a turbine engine parameter used to monitor combustion and turbine conditions and to set thrust limits, since it often reaches limits before rotational speed.

The ratio of turbine discharge pressure to compressor inlet pressure, used as a thrust-setting parameter on some turbojet and turbofan engines.

A device that redirects engine exhaust or fan airflow forward to produce reverse thrust, aiding deceleration after landing and during a rejected take-off.

A pilot's mistaken perception of aircraft attitude or motion, typically caused by conflicting vestibular and visual cues in low visibility or during acceleration and turning manoeuvres.

A false sensation of pitch caused by linear acceleration or deceleration, in which a rapid acceleration is misperceived as a nose-up attitude.

The inner-ear organs, semicircular canals and otoliths, that sense angular and linear acceleration but cannot reliably distinguish gravity from sustained acceleration, contributing to illusions.

A deficiency of oxygen reaching body tissues, which at altitude results from reduced oxygen partial pressure and impairs night vision, judgement, and consciousness if uncorrected.

The period after loss of oxygen supply during which a person can still perform useful, deliberate actions before incapacitation, shortening rapidly as altitude increases.

Training and practice in effective use of all available resources, including crew, equipment, and information, to improve safety, communication, and decision-making in flight operations.

A framework for recognising external threats and crew errors, then trapping or mitigating them before they produce an undesired aircraft state.

The largest circle that can be drawn on a sphere, whose plane passes through the centre, representing the shortest surface distance between two points.

A line on the Earth's surface crossing every meridian at the same angle, appearing straight on a Mercator chart but generally longer than the great circle track.

A cylindrical map projection on which meridians are parallel straight lines and the scale expands with latitude, making rhumb lines straight but distorting high-latitude areas.

A precision approach aid providing lateral guidance from a localiser and vertical guidance from a glide path, referenced to decision height and runway touchdown area.

The vertical guidance beam of an ILS, typically set at about three degrees, defining the descent profile to the runway touchdown zone.

A specified altitude or height in a precision approach at which a missed approach must be initiated if the required visual reference has not been established.

A magnetic bearing from a VOR station, displayed by the aircraft receiver, which together with distance defines the aircraft's position relative to that station.

A radio navigation system that measures the slant range from the aircraft to a ground transponder by timing signal round trips, usually paired with VOR or TACAN.