PPL Flight Performance and Planning key terms

The total length of runway plus any clearway, measured from the start of the take-off run, within which an aircraft can complete its take-off and reach a defined height.

The length of runway declared suitable and available for the ground run of an aircraft taking off, excluding any clearway or stopway.

The length of the take-off run available plus any stopway, declared as suitable for an aircraft to accelerate and then stop safely after an engine failure.

A defined rectangular area beyond the runway end, free of obstacles, over which an aircraft may climb to a specified height after take-off; it counts toward TODA but not TORA.

A defined rectangular area beyond the runway end, prepared so an aircraft can stop on it after an aborted take-off; it adds to ASDA but is not part of the take-off run.

The runway length at which the accelerate-stop distance equals the take-off distance to the specified screen height, giving the shortest field for a given weight and conditions.

The regulatory height above the runway surface that an aircraft must reach at the end of the take-off distance, typically 35 feet for light twins and larger aircraft.

Pressure altitude corrected for non-standard temperature, expressing how thin the air is; higher values reduce engine power, propeller thrust and wing lift, lengthening take-off and climb.

The altitude shown on an altimeter set to the standard datum of 1013.25 hPa (29.92 inHg), used as the reference for performance charts and flight levels.

The altimeter subscale setting that, when applied at aerodrome level, makes the altimeter read the elevation above mean sea level; used for terrain clearance.

The altimeter subscale setting that makes the altimeter read zero on the aerodrome reference point, so it displays height above the aerodrome rather than altitude.

The speed shown on the airspeed indicator, derived from the difference between pitot (impact) pressure and static pressure; it is the value used for most aircraft performance tables.

Indicated airspeed corrected for position and installation error of the pitot-static system; it is close to true airspeed at sea level in standard conditions.

The actual speed of the aircraft through the air mass, found by correcting calibrated airspeed for density altitude; used for navigation and for calculating wind effects.

The speed of the aircraft relative to the ground, equal to true airspeed adjusted for the wind component along the flight path.

The part of the wind acting along or across the intended flight path: headwind or tailwind along track, and crosswind across it, each affecting take-off, landing and navigation.

The maximum demonstrated or permitted crosswind component, published in the flight manual, at which the aircraft can be safely taken off or landed.

The crosswind component shown during certification to be controllable by a pilot of average skill; it is a demonstrated value, not an absolute structural limit, unless the manual states otherwise.

The highest mass permitted for the aircraft at the start of the take-off run, set by the manufacturer and approved in the flight manual for structural and performance reasons.

The highest mass at which the aircraft may land, determined by structural and go-around/climb performance limits; fuel may need to be burned off to reach it.

The mass of the aircraft including crew, passengers, baggage and usable payload but excluding usable fuel; it must not exceed the published maximum zero-fuel mass.

The mass of the aircraft with unusable fuel, full operating fluids and standard equipment, but without crew, passengers, baggage or usable fuel; the starting point for mass and balance.

The difference between maximum take-off mass and basic empty mass, representing the total mass available for fuel, crew, passengers and baggage.

The revenue or operational load carried, such as passengers, baggage and cargo, excluding fuel and crew; it is limited by mass, volume and centre-of-gravity constraints.

The point through which the total weight of the aircraft acts; its position, expressed as a distance aft of the datum, must stay within the approved forward and aft limits.

An arbitrary reference point or plane from which all longitudinal distances (arms) are measured when calculating moments for mass and balance.

The horizontal distance from the datum to the point where a mass acts; multiplied by the mass, it gives the moment used to locate the centre of gravity.

The product of a mass and its moment arm, expressing the turning effect about the datum; total moment divided by total mass gives the centre-of-gravity position.

The chart area, bounded by forward and aft centre-of-gravity limits and mass limits, within which the loaded aircraft must remain for every phase of flight.

The most forward permitted centre-of-gravity position, beyond which elevator authority and take-off/landing performance may be insufficient and stall speed increases.

The most rearward permitted centre-of-gravity position, beyond which stability and stall recovery may be degraded and control forces become very light.

The maximum density altitude at which the aircraft can maintain a specified climb rate, typically 100 feet per minute for normally aspirated light aircraft.

The density altitude at which the maximum climb rate falls to zero, so the aircraft can no longer climb; it is higher than the service ceiling.

The vertical speed achieved, usually expressed in feet per minute; it depends on excess power and is reduced by high mass, high density altitude and increased drag.

The climb gradient, or height gained per unit of horizontal distance; it depends on excess thrust and determines obstacle clearance, unlike rate of climb.

The margin of height above terrain or obstacles along a take-off or approach path, achieved by satisfying the required climb gradient and departure procedure.

The minimum fuel that must remain at destination or alternate, prescribed by regulation for contingency, diversion and holding, and included in the flight plan.

The fuel required from take-off at the departure aerodrome to landing at the destination, calculated from distance, power setting, wind and mass.

The process of calculating trip, reserve, taxi and contingency fuel so that the planned mass stays within limits and the required reserves remain intact.