ATPL Flight Performance and Planning key terms

The vertical distance between the lowest point of the aircraft and the take-off surface at the end of the take-off distance available, normally 35 ft for a dry runway and 15 ft for a wet or contaminated runway.

The length of the take-off run available plus the length of any clearway declared by the aerodrome operator, measured from the start of the take-off run.

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

A defined rectangular area beyond the runway end, under aerodrome control, free of obstacles and sloping no more than 1.25 per cent upward, over which the aircraft can climb to screen height.

A defined rectangular area beyond the runway end, prepared and suitable for an aircraft to stop during a rejected take-off, without causing structural damage.

The length of the take-off run available plus the length of any stopway, representing the distance within which an aircraft can accelerate to V1 and then stop.

The runway length at which the accelerate-stop distance equals the take-off distance to screen height, giving the shortest field from which the aircraft can both continue and stop safely.

The maximum speed at which the flight crew must decide to reject a take-off and still stop within the accelerate-stop distance available, and the minimum speed at which a continued take-off is possible.

The speed that must be reached by the end of the take-off distance and maintained to screen height, giving the aircraft a defined climb gradient with one engine inoperative.

The minimum required climb gradient in the take-off configuration with one engine inoperative, gear retracted and take-off flap set, typically 2.4 per cent for twin-engine aeroplanes.

The gross take-off flight path reduced by a fixed gradient decrement (0.8 per cent for twins, 0.9 per cent for three engines, 1.0 per cent for four engines) to give a conservative clearance path.

The minimum height above all obstacles in the take-off flight path, usually 35 ft vertically and 90 m plus 0.125 D horizontally, within which the net flight path must remain clear.

The height lost by an aircraft flying at a constant cruise level while one engine is inoperative, used to define the en-route net flight path for engine-failure drift-down procedures.

The highest pressure altitude at which an aircraft can maintain level flight with one engine inoperative at a specified speed and mass, defined by the available thrust minus drag.

The pressure altitude selected for the en-route phase, chosen to satisfy terrain clearance, air traffic control, fuel efficiency and engine-out drift-down requirements.

The pressure altitude at which the aircraft achieves the best specific range for its current mass and conditions, often close to the crossover altitude between maximum-range cruise and high-speed cruise.

The distance an aircraft can fly per unit of fuel consumed, normally expressed in nautical miles per kilogram, and used to compare cruise efficiency at different levels and speeds.

The mass of fuel consumed per unit of time by the engines, normally expressed in kilograms per hour, and the primary input for trip fuel and endurance calculations.

The fuel required from take-off to touchdown at the destination, including climb, cruise, descent and any anticipated approach fuel, but excluding reserves and taxi fuel.

Fuel carried to cover unforeseen factors such as deviation from planned route, weather, or routing, normally 5 per cent of trip fuel or an equivalent statistical allowance.

Fuel that must remain at the end of the flight, typically 30 minutes of holding at 1500 ft above the alternate aerodrome, and may not be planned for use.

Fuel required to fly from the destination to the selected alternate aerodrome, including approach, landing and any missed-approach fuel at the alternate.

Fuel added when the minimum required reserves are insufficient for a specific scenario, such as a destination with no alternate or a flight to an isolated aerodrome.

An aerodrome where no suitable alternate exists within 60 minutes of flying time, requiring specific additional fuel planning under the applicable operational rules.

An aerodrome selected before departure at which an aircraft can land if a diversion becomes necessary during the en-route phase, for example after an engine failure or depressurisation.

The point along a route at which the time to fly to either of two diversion aerodromes is equal, used to define the critical decision point for diversion planning.

The furthest point along a route from which the aircraft can return to the departure aerodrome with the fuel remaining, accounting for wind and fuel reserves.

The worst-case fuel computation, such as depressurisation or engine failure at the most critical point, used to confirm that reserves are sufficient for the planned route.

The document prepared by the operator for a specific flight, containing route, fuel, mass, performance and alternate data, signed by the commander as acceptance of the plan.

A flight plan generated by a flight-planning system using wind, temperature, aircraft performance and route data, producing waypoint times, fuel burns and mass estimates.

The process of revising the flight plan in flight, for example after a diversion, weather change or engine failure, recalculating fuel, route and alternate requirements.

The continuous comparison in flight of fuel remaining against the flight plan, identifying deviations early enough to adjust route, speed or destination.

The length of runway declared available and suitable for the ground run of a landing aeroplane, from the threshold to the end of the runway.

The actual distance needed to land and stop from screen height, factored by 1.67 for dry runways or 1.92 for wet runways to give the required landing distance.

The reported state of the runway surface, such as dry, wet, or contaminated with standing water, snow or slush, which determines braking action and the applicable performance factors.

A runway where more than 25 per cent of the surface is covered by standing water, slush, snow or ice beyond a defined depth, requiring contaminated-runway performance data.

Loss of tyre contact with the runway caused by a film of water, reducing braking effectiveness and directional control, and occurring above a speed related to tyre pressure.

The certified range of centre-of-gravity positions, expressed as a percentage of mean aerodynamic chord, within which the aircraft may be operated in flight.

The chord of an equivalent rectangular wing producing the same pitching moment as the actual wing, used as the reference for expressing centre-of-gravity position.

The total mass of the aircraft ready for service, including crew, crew baggage, catering, water and other operational items, but excluding usable fuel and traffic load.

The mass of the aircraft and its contents excluding usable fuel, equal to dry operating mass plus traffic load, and limited by the maximum zero fuel mass.

The total mass of passengers, baggage, cargo and mail carried on a flight, added to dry operating mass to give zero fuel mass.

A scaled number representing a centre-of-gravity position along the fuselage, used on load sheets so that moments can be added and converted back to a CG position.

A change to the load made after the load sheet has been prepared, such as added or offloaded baggage, requiring the commander to verify the CG remains within limits.

The document showing the distribution of mass on a flight, from which zero fuel mass, take-off mass, landing mass and the centre-of-gravity position are derived and checked against limits.