EASA PPL key terms

The maximum speed at which full deflection of a single flight control may be applied without overstressing the airframe. It falls as mass decreases, so above it control inputs must be smooth and limited.

The ratio of lift produced to the aircraft's weight, expressed in g. It rises steeply in turns and pull-ups, and the structure is certified for a defined positive and negative limit.

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

The lowest indicated airspeed at which the wing can produce enough lift to support the aircraft in a given configuration and mass. It increases with mass, load factor and forward centre of gravity.

Drag created as a by-product of lift, caused by the spanwise flow and wingtip vortices. It is greatest at high angle of attack and low speed, and decreases as speed increases.

The speed giving the greatest still-air distance per unit of height lost, found where total drag is minimum. It increases with mass but is unaffected by wind, though wind changes the achieved range.

The tendency of wings set at an upward angle to the fuselage to generate a rolling moment away from a sideslip. It contributes to lateral stability and interacts with directional stability in Dutch roll.

The initial tendency of an aircraft, after a disturbance, to return towards its original flight condition. It may be positive, neutral or negative, and is assessed separately about each axis.

The density altitude at which an aircraft in a specified configuration can no longer climb faster than a defined small rate, commonly 100 feet per minute for piston aeroplanes.

Pressure altitude corrected for temperature deviation from the standard atmosphere. High temperature, low pressure or high humidity raise it and degrade engine power, propeller thrust, lift and climb performance.

The altitude indicated when the altimeter subscale is set to 1013.25 hPa. It is the reference used for flight levels and for performance charts based on the standard atmosphere.

The certified forward and aft limits of centre of gravity position for a given mass. Operating outside them reduces controllability, increases trim drag or makes rotation and stall recovery unsafe.

A document recording the distribution of mass in the aircraft and the resulting centre of gravity position. It confirms the aircraft is within mass and balance limits before departure.

The highest mass at which the aircraft is certified to begin the take-off run. It may be limited further on the day by runway length, obstacle clearance, climb gradient or tyre speed.

The shortest runway from which a multi-engine aircraft can either continue the take-off after an engine failure at the decision speed or stop, with equal distance for both cases.

The altitude at or below which the altimeter is set to local pressure and altitude is used. Above it, the standard setting 1013.25 hPa is used and heights are expressed as flight levels.

The lowest flight level available for use above the transition altitude. Its value varies with the local pressure so that adequate separation exists between the two.

The minimum flight visibility and distance from cloud that must be maintained in visual meteorological conditions. The values depend on airspace class, altitude and, in some cases, indicated airspeed.

A clearance allowing flight within a control zone in conditions below visual meteorological criteria, subject to the pilot remaining clear of cloud and in sight of the surface.

Airspace of defined dimensions within which air traffic control service is provided, classified from A to E. Classes A to D require a clearance; class E requires one only for instrument flight.

A mandatory instruction issued by the competent authority to correct an unsafe condition. It must be complied with within the stated time or usage limit for the aircraft to remain airworthy.

The document confirming that an individual aircraft conforms to its approved type design and is in a condition for safe operation. It remains valid only while maintenance and mandatory checks are kept current.

An approved document listing which instruments and equipment may be inoperative for dispatch, together with any operating conditions or limitations that then apply.

Ice forming in the carburettor due to the cooling effect of fuel vaporisation and venturi pressure drop. It can occur at outside air temperatures well above freezing and causes a gradual power loss.

A control that admits warmed air to the carburettor to melt or prevent ice. Applying it enriches the mixture and may cause a temporary further power loss as ice melts.

A pre-take-off test in which each magneto is selected in turn to confirm both ignition circuits operate and the engine runs acceptably on each, with a limited permitted drop in rpm.

A shortage of oxygen reaching the body tissues. In aviation it commonly arises from high altitude without supplemental oxygen, and causes impaired judgement before the pilot notices symptoms.

The period after loss of adequate oxygen supply during which a person can still take effective corrective action. It shortens rapidly as altitude increases and is reduced by cold and exertion.

Over-breathing that lowers carbon dioxide in the blood, producing dizziness, tingling and visual disturbance. Its symptoms resemble hypoxia, and the treatment is to slow the breathing rate.

A mistaken perception of the aircraft's position or motion, typically when external visual references are lost. The pilot must trust the instruments rather than sensations.

A false sensation of pitching up or down caused by linear acceleration or deceleration, for example during take-off or go-around. The pilot may wrongly push or pull the control column.

The altimeter subscale setting that makes the instrument read elevation above mean sea level when the aircraft is on the ground at that location. It is used below the transition altitude.

The altimeter subscale setting that makes the instrument read zero on the ground at a specified reference point, so it indicates height above that point rather than altitude.

The angular difference between true north and magnetic north at a given place, shown on charts and changing slowly over time. It is applied when converting between true and magnetic directions.

The error of a magnetic compass caused by the aircraft's own magnetic fields. It varies with heading and is recorded on a compass correction card.

A line on a chart joining points of equal magnetic variation. Crossing it changes the value that must be applied between true and magnetic bearings.

A defined reference atmosphere with sea-level pressure 1013.25 hPa, temperature 15 degrees Celsius and a fixed lapse rate, used to calibrate altimeters and performance data.

The lowest altitude in the atmosphere at which the air temperature is zero degrees Celsius. Above it, airframe and carburettor icing become likely in visible moisture.

A narrow band of intense convective activity, often ahead of a cold front, producing severe turbulence, heavy showers, hail and strong gusty surface winds.

The requirement for a pilot to repeat back safety-related parts of an ATC clearance, such as route, level, heading and frequency, so the controller can verify correct reception.

An authorisation from air traffic control for an aircraft to proceed under specified conditions. It does not relieve the pilot of responsibility for separation from terrain or for compliance with rules.