CARC PPL Theory key terms

A set of rules under which a pilot may operate an aircraft mainly by looking outside the cockpit, provided minimum visibility and distance-from-cloud limits are met. A clearance is still required in controlled airspace.

Airspace of defined dimensions within which air traffic control service is provided to flights, and in which all aircraft normally require an ATC clearance before entry. Classes A to E are controlled.

An authorisation from ATC for an aircraft to proceed under specified conditions. It does not relieve the pilot in command of responsibility for terrain clearance, collision avoidance or compliance with the law.

The rule that cruising levels are chosen according to magnetic track: 000 to 179 degrees use odd thousands, 180 to 359 degrees use even thousands, with VFR flights adding 500 feet between the two systems.

The altitude at or below which an aircraft's vertical position is expressed as altitude and above which it is expressed as flight level. It is published for each aerodrome or area and marks the change of pressure datum.

The fixed reference pressure of 1013.25 hectopascals (29.92 inches of mercury) set on the altimeter subscale when flying at or above the transition altitude, so that all aircraft share a common datum.

A surface of constant atmospheric pressure related to the standard pressure setting, expressed in hundreds of feet. Flight level 100 means 10,000 feet indicated on the standard pressure setting.

The local pressure value set on the altimeter subscale so that the instrument indicates height above a chosen reference, such as aerodrome elevation or mean sea level. It is supplied by ATC or the aerodrome service.

The altimeter subscale setting that, when applied at aerodrome elevation, makes the altimeter read elevation above mean sea level. It is the normal setting for approach and landing and for flight below the transition altitude.

The altimeter subscale setting that makes the altimeter read zero at a specified reference point, usually the aerodrome runway threshold. It is used for circuit work but not for terrain separation between aerodromes.

The mandatory repetition by a pilot of safety-related ATC instructions such as clearances, runway and heading instructions, and altimeter settings, allowing the controller to confirm the message was received and understood correctly.

A radio message giving an aircraft's identification, position, time, level and next position with estimated time, used where ATC requires regular reports along a route or in non-radar airspace.

The point through which the total weight of the aircraft acts. It must stay within a certified forward and aft range for the aircraft to be controllable and stable in flight.

The horizontal distance between a reference datum and a mass item, such as a passenger seat or fuel tank. Multiplying the mass by its moment arm gives the moment used to locate the centre of gravity.

The mass of an aircraft with all equipment and unusable fuel and oil included, but without crew, passengers, baggage or usable fuel. It is the starting figure for every mass and balance calculation.

The difference between the maximum take-off mass and the basic empty mass. It represents everything the aircraft may carry: fuel, crew, passengers and baggage, each of which must still fit within its own limits.

The highest mass at which the aircraft is certified to begin the take-off run. It may be reduced for a particular flight by performance considerations such as runway length, obstacles or temperature.

The pressure altitude corrected for temperature deviation from standard. High density altitude reduces engine power and lift, so take-off and climb performance are worse than the pressure altitude alone suggests.

The altitude indicated when the altimeter is set to the standard pressure setting. It is the basis for performance charts, which then correct for temperature to give density altitude.

Vx is the speed giving the greatest gain in height for a given horizontal distance, used to clear obstacles. Vy gives the greatest rate of climb and is normally used for routine climb.

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

The angle of attack at which the wing produces maximum lift and beyond which it stalls. It is a fixed value for a given wing and is reached at any speed if the angle becomes large enough.

The lowest indicated airspeed at which level flight can be maintained in a given configuration, reached at the critical angle of attack. It rises with weight, load factor and forward centre of gravity.

Drag produced as a by-product of lift, caused by the wingtip vortices and strongest at low speed and high angle of attack. It decreases as speed increases, unlike parasite drag.

A condition in which the body tissues receive insufficient oxygen. Early signs include euphoria, poor judgement and impaired vision, and the pilot may not notice them, so prompt use of supplemental oxygen is essential.

Over-breathing that lowers carbon dioxide in the blood, causing dizziness, tingling and faintness that resemble hypoxia. Slowing the breathing rate, or breathing into a bag, usually relieves it.

A false perception of the aircraft's attitude or motion, typically when outside visual references are lost. The pilot must disregard body sensations and trust the flight instruments to recover.

The period after loss of oxygen supply during which a person can still take effective corrective action. It shortens sharply as altitude increases and is very brief above about 40,000 feet.

Rules governing flight in which the pilot navigates and controls the aircraft mainly by reference to instruments, under an ATC clearance and within specified equipment and qualification requirements.

The minimum flight visibility and distance from cloud that a VFR flight must maintain, which vary with airspace class and altitude. If they cannot be maintained the flight must not continue under VFR.

A ground beacon that transmits signals allowing an aircraft receiver to determine the magnetic bearing from the station. A course line is selected with the omni-bearing selector and flown using the deviation indicator.

A magnetic bearing measured from a VOR station, expressed from 000 to 359 degrees. Flying outbound on a radial means tracking away from the station along that bearing.

A transponder-based system that measures slant range from the aircraft to a ground station, usually displayed in nautical miles. The reading is slightly greater than the ground distance when the aircraft is high.

A precision approach aid providing lateral guidance from a localiser and vertical guidance from a glide path, normally aligned with the runway. It allows approach to a decision height in low visibility.

The height or altitude on a precision approach at which a missed approach must be initiated if the required visual reference to continue has not been established. It protects against continuing an unstable approach.

A published procedure followed when an approach cannot be completed to a landing, or when instructed by ATC. It is flown from a defined point and guarantees obstacle clearance back to a safe altitude.

A routine coded report of observed weather at an aerodrome, including wind, visibility, cloud, temperature and pressure. Pilots decode it to build a picture of current conditions before departure or arrival.

A coded forecast of expected weather at an aerodrome for a stated period, including wind, visibility and cloud. It is used for flight planning and for deciding on alternate aerodromes.

An aerodrome to which a flight may proceed if a landing at the destination is not possible. It must be nominated in the flight plan when weather or fuel requirements demand it.

A change in wind speed or direction over a short distance, most dangerous at low level during approach or departure. It can cause sudden loss of airspeed and must be reported and avoided.