KCAA CPL Theory key terms

Weather conditions in which flight visibility and distance from cloud equal or exceed the minima set for the airspace class. In these conditions the pilot may navigate and keep clear of traffic mainly by outside visual reference.

Conditions below the visual minima for the airspace class, where flight must be conducted mainly by reference to instruments. In controlled airspace an instrument rating and an IFR clearance are normally required.

A flight conducted under visual flight rules, in which the pilot maintains separation from cloud and terrain by visual reference and remains in VMC. A clearance is required only in controlled airspace.

A flight conducted under instrument flight rules, separated from other traffic by air traffic control and normally following published routes and procedures. The pilot must hold an instrument rating and the aircraft must be suitably equipped.

A clearance allowing a flight in controlled airspace to operate below the normal VMC minima while remaining clear of cloud and in sight of the surface. It is requested by the pilot and subject to ATC approval and local limits.

An authorisation from air traffic control for a flight to proceed under specified conditions, such as route, level, or manoeuvre. It does not relieve the pilot in command of responsibility for terrain and obstacle clearance.

The pilot's repetition to ATC of safety-related clearance elements, including route, altitude, heading, speed, and frequency instructions. Correct read-back confirms that the instruction was received and understood as transmitted.

A four-digit octal code set on the aircraft transponder, assigned by ATC or selected from published procedures. It allows the aircraft's radar return to be paired with a flight identity and service.

An airborne radio receiver and transmitter that replies to ground radar interrogations. Mode A gives identity, Mode C adds pressure altitude, and Mode S allows selective addressing and data exchange.

The method of deriving aircraft altitude from a pressure altimeter referenced to a selected datum. Correct setting of QNH, QFE, or standard pressure is essential for terrain clearance and vertical separation.

The lowest flight level available for use above the transition altitude. Below it, altitudes are flown on the local pressure setting; at and above it, flight levels use standard pressure.

A surface of constant pressure altitude referenced to the standard pressure setting of 1013.25 hPa and expressed in hundreds of feet. It provides a common vertical reference for all aircraft above the transition level.

A mandatory instruction issued by the state of registry requiring inspection, modification, or limitation of an aircraft or component to correct an unsafe condition. Compliance is legally required and must be recorded in the aircraft documents.

The document certifying that an aircraft conforms to an approved type design and is considered safe for flight when properly maintained. It remains valid only while mandatory maintenance and modification requirements are met.

A certification, signed by authorised maintenance personnel, confirming that specified work has been completed and the aircraft or component is fit for return to service. It must be issued before flight after scheduled or unscheduled maintenance.

Two independent magneto circuits, each firing one spark plug per cylinder. The arrangement gives redundancy after a single failure and improves combustion speed and efficiency, which is checked during engine run-up.

A self-contained engine-driven generator that produces high-voltage pulses for the spark plugs without an external battery. Its timing and function are checked before take-off by selecting each magneto in turn.

Ice formation in the carburettor venturi and throttle area caused by fuel vaporisation and pressure drop, most likely at temperatures between about -5 and +15 degrees Celsius with high humidity. It can occur without visible airframe ice.

The pressure altitude corrected for non-standard temperature, representing the altitude at which the aircraft performance would occur in a standard atmosphere. High values reduce lift, engine power, and climb performance.

The altitude indicated when the altimeter is set to standard pressure, 1013.25 hPa. It is the basis for flight levels and for performance charts that are then corrected for temperature to give density altitude.

The point at which the aircraft's total weight is considered to act. Its position must remain within the certified forward and aft limits for control effectiveness and stability in all loading conditions.

The calculation of total aircraft mass and the position of the centre of gravity from the masses and arms of fuel, occupants, baggage, and cargo. It must be completed before every flight.

A condition in which body tissues receive insufficient oxygen, causing impaired judgement, euphoria, and loss of consciousness. It may develop insidiously at altitude and is countered by supplemental oxygen and descent.

A false perception of the aircraft's attitude or motion arising when vestibular and visual cues conflict, particularly without external visual reference. Recovery depends on trusting the flight instruments rather than bodily sensations.

A false sensation of pitching up during acceleration, or pitching down during deceleration, caused by linear acceleration stimulating the otolith organs. The pilot may respond with an inappropriate control input unless instruments are trusted.

Excessive breathing rate or depth that lowers blood carbon dioxide, producing dizziness, tingling, and muscle cramps. Symptoms resemble hypoxia, and treatment is to slow the breathing rate and breathe normally.

The altimeter setting that makes the instrument indicate elevation above mean sea level at the aerodrome when the aircraft is on the ground. It is used below the transition altitude for terrain clearance.

The altimeter setting that makes the instrument read zero at the aerodrome reference point. It is used in some aerodrome circuits and approach procedures to give height above the aerodrome.

The altitude, in feet above mean sea level, below which the altimeter is set to the local pressure setting. Above it, the standard pressure setting is used and altitudes become flight levels.

A line on a chart joining points of equal wind speed. Isotachs are used with pressure patterns to locate jet streams and areas of strong wind shear.

A narrow, fast-moving band of wind near the tropopause, typically thousands of kilometres long and a few kilometres deep. It strongly affects cruise time, fuel planning, and clear-air turbulence.

A change in wind speed or direction over a short distance, horizontally or vertically. Low-level shear on approach or departure can cause sudden airspeed and lift changes and is a major hazard.

The shortest path between two points on the surface of a sphere, formed by the intersection of the surface with a plane through the centre. Its track direction changes continuously along the route.

A line crossing every meridian at the same angle, appearing straight on a Mercator chart. It is easier to follow than a great circle but is not the shortest distance except along the equator or a meridian.

The angular difference between true north and magnetic north at a given place, varying with position and slowly with time. It is applied when converting between true and magnetic directions.

The initial tendency of an aircraft, after a disturbance in angle of attack, to return to its original state. Positive stability resists disturbance, neutral stability holds the new state, and negative stability diverges.

The angle between the wing chord line and the relative airflow. Lift increases with angle of attack up to the critical value, beyond which the wing stalls.

A loss of lift caused by exceeding the critical angle of attack, independent of airspeed or attitude. Recovery requires reducing the angle of attack, typically by lowering the nose.

An instruction for the pilot to press the transponder identify button, which causes a distinctive radar display to confirm the aircraft's position. It is used when controller identification is uncertain.

A ground radio beacon that transmits signals allowing an aircraft to determine its magnetic bearing from the station. It supports route navigation and, with distance measuring equipment, position fixing.

A transponder-based system that measures slant range from the aircraft to a paired ground station. The indication is line-of-sight distance, not ground distance, and includes altitude error overhead the station.

A precision approach aid providing lateral guidance from a localiser and vertical guidance from a glide path, with markers or DME for distance. It allows descent to low decision heights in suitable weather.