Brunei DCA CPL(A) Performance key terms

The length of the take-off run available plus the length of any clearway provided, measured from the point where the take-off run begins. It limits how far an aeroplane may travel from brake release to the point where it reaches 35 ft above the runway surface.

The length of runway declared available and suitable for the ground run of an aeroplane taking off. It excludes any clearway or stopway and is used to check that the aeroplane can accelerate and lift off within the paved surface.

The length of the take-off run available plus the length of any stopway provided. It defines the distance within which an aeroplane must be able to accelerate to a decision speed and then stop safely after an engine failure.

The length of runway declared available and suitable for the ground run of a landing aeroplane, measured from the threshold to the end of the paved surface. It is the limit against which the landing distance required, factored for conditions, must be compared.

A defined rectangular area beyond the end of the take-off run available, under the control of the aerodrome operator, clear of obstacles and sloping no more steeply than a specified limit. It allows part of the initial climb to be counted in the take-off distance available.

A defined rectangular area beyond the end of the take-off run available, prepared so that an aeroplane can be stopped without structural damage during an aborted take-off. It adds to the accelerate-stop distance available but not to the take-off run available.

The runway length at which the accelerate-stop distance equals the take-off distance to 35 ft, so an engine failure at V1 leaves equal distance to stop or continue. It represents the minimum field length for a given weight and condition.

The speed at which, following an engine failure, the pilot can either continue the take-off and reach the required screen height or stop within the remaining runway. It is chosen before take-off and must be at least the minimum control speed on the ground.

The speed at which the pilot initiates rotation to raise the nose and increase pitch attitude, so the aeroplane reaches take-off safety speed by the time it leaves the ground. It is normally above V1 and below V2.

The minimum speed that must be reached by the time the aeroplane is 35 ft above the take-off surface, and then maintained during the initial climb with one engine inoperative. It ensures adequate climb gradient and controllability.

The height above the take-off or landing surface at which the aeroplane is assumed to reach a defined point in the flight path, typically 35 ft for take-off and 50 ft for landing. Performance distances are referenced to crossing this height.

The ratio of height gained to horizontal distance travelled, usually expressed as a percentage. It determines whether an aeroplane can clear obstacles or terrain along a departure or en-route segment, and varies with weight, temperature and altitude.

The vertical speed of an aeroplane, expressed in feet per minute. It depends on excess thrust or power over drag and is affected by weight, altitude, temperature and configuration, and is used to check en-route climb requirements.

The highest altitude at which an aeroplane can maintain a specified maximum rate of climb, often 100 ft per minute for piston-engine types. Above this altitude climb performance becomes marginal for normal operations.

The altitude at which the maximum rate of climb of an aeroplane falls to zero, so level flight can no longer be sustained in the prevailing configuration and power setting. It lies above the service ceiling and is not a normal operating limit.

A defined model of the atmosphere used to compare aircraft performance, with sea-level pressure 1013.25 hPa, temperature 15 degrees Celsius, and a lapse rate of 1.98 degrees Celsius per 1000 ft up to 36,090 ft. It provides a common reference for chart data.

The difference between the actual outside air temperature at a given level and the standard atmosphere temperature for that level, expressed in degrees Celsius. Positive values mean warmer than standard and generally degrade performance.

The altitude indicated when the altimeter subscale is set to 1013.25 hPa, independent of local pressure settings. It is the altitude used with temperature to determine density altitude and to enter most performance charts.

The altitude in the standard atmosphere at which the air density equals the actual density at the point concerned. It combines pressure altitude and temperature and is the key input for take-off, climb and landing performance in hot or high conditions.

The reduction in air density caused by water vapour, which is less dense than dry air at the same pressure and temperature. High humidity slightly increases take-off distance and reduces climb performance, though less than temperature does.

Take-off or landing at aerodromes with high elevation and high temperature, where low air density reduces engine power, propeller or fan thrust, and lift for a given true airspeed. Performance margins shrink and weight or configuration may need adjustment.

The part of the wind velocity acting along the runway centreline, either opposing or assisting the ground run. A headwind shortens take-off and landing distances, while a tailwind lengthens them and is normally limited by the flight manual.

The part of the wind velocity acting perpendicular to the runway centreline. It affects directional control during take-off and landing and must not exceed the maximum demonstrated value published in the flight manual.

The change in take-off or landing distance caused by the runway not being level. An upslope increases the take-off ground run and a downslope increases the landing roll, and charts usually give corrections per percent of slope.

The state of the runway in terms of material and contamination, such as dry asphalt, wet grass, slush, snow or standing water. It changes rolling friction and braking action and therefore the distances required for take-off and landing.

A runway whose significant portion of the surface is covered by water, slush, snow, ice or other substances that reduce friction and may cause spray or drag. Landing and accelerate-stop distances increase markedly and must be taken from the appropriate supplement.

Loss of tyre contact with the runway because a film of water lifts the tyre, sharply reducing braking and directional control. It becomes more likely at high speed, with low tyre pressure and with deep standing water.

The effectiveness of wheel braking on a runway surface, reported as good, medium, poor or by a measured friction value. It is used to adjust landing distance calculations when the surface is wet or contaminated.

The runway distance needed to land and stop from crossing the threshold at 50 ft, multiplied by the operational safety factor required by the rules. It must not exceed the landing distance available at the destination or alternate.

A threshold located at a point on the runway other than the physical beginning, usually because of obstacles, terrain or noise abatement. The paved area before it may be used for take-off but not for landing, reducing the landing distance available.

The margin maintained between an aeroplane's flight path and obstacles or terrain along a departure, approach or en-route segment. It is checked using published gradients and the net take-off flight path, which already includes a required reduction for climb performance.

The take-off flight path reduced by a specified gradient decrement, such as 0.8 percent for two-engine aeroplanes, to account for pilot technique and turbulence. It must clear all obstacles by the required margin.

The highest mass at which the aeroplane may begin the take-off run, limited by structure, field length, obstacle clearance and climb requirements. The permitted value for a given flight is the lowest of these limiting masses.

The take-off mass permitted for a specific runway, temperature, pressure altitude and obstacle situation, found by applying the limiting performance requirements. It is often below the structural maximum take-off mass and must be respected for the actual conditions.

The highest mass at which the aeroplane may land, set by structural limits and by the landing distance available at the destination. If the take-off mass exceeds it, fuel must be burned off or jettisoned before landing.

The forward and aft boundaries within which the aeroplane's centre of gravity must remain for safe control and performance. An aft limit reduces stability, while a forward limit increases elevator load and can lengthen the take-off run.

The process of calculating the total mass and the position of the centre of gravity by summing the moments of the empty aeroplane, fuel, occupants and baggage. Correct results ensure the aeroplane stays within mass and CG limits and performs as charted.

The horizontal distance from the reference datum to the point where a mass is located. Multiplying it by the mass gives the moment used to compute the centre of gravity position in weight and balance calculations.

A take-off performed with a thrust or power setting lower than the maximum approved, chosen to reduce engine wear while still meeting all field, obstacle and climb requirements. It must not be used when performance margins are already tight.

A technique of reducing take-off thrust by using a fictitious higher outside air temperature, provided the resulting performance still meets the required field length, obstacle and climb gradients. It lowers engine stress without changing actual conditions.