NCAA CPL Flight Performance & Planning key terms

The mass of the aeroplane as delivered, including unusable fuel, full engine oil, and all fixed equipment, but excluding crew, usable fuel, and payload. It is the starting point for every mass and balance calculation.

Basic empty mass plus crew, crew baggage, catering, potable water, and other operational items. It excludes usable fuel and traffic load, so it represents the aeroplane ready for a flight apart from fuel and payload.

Dry operating mass plus take-off fuel. It is the mass of the aeroplane at brake release with no traffic load, and it is used to check that fuel alone does not push the aeroplane past structural or performance limits.

The total mass of the aeroplane at the start of the take-off run, comprising dry operating mass, take-off fuel, and traffic load. It must not exceed the maximum certified take-off mass or the performance-limited mass for the conditions.

The mass of the aeroplane at touchdown, equal to take-off mass minus trip fuel. It is compared with the maximum certified landing mass and with any performance-limited landing mass at the destination or alternate.

A structural limit on the mass of the aeroplane without usable fuel. It protects the wing root and fuselage structure from the bending loads that a heavy fuselage combined with light fuel would produce.

The highest mass at which the aeroplane is certified to begin the take-off run. It is a structural and certification limit, separate from the lower performance-limited take-off mass that the runway and obstacles may impose.

The sum of passengers, baggage, cargo, and mail carried, including the mass of any non-crew persons on board. It is added to dry operating mass and fuel to build up take-off mass.

The amount by which the allowed take-off mass exceeds the actual take-off mass. It tells the crew how much extra fuel or payload could be carried without breaching the limiting mass for the sector.

The horizontal distance of a mass item from the reference datum, measured along the fuselage. Each item's moment is its mass multiplied by its arm, and the sum of moments divided by total mass gives the CG position.

A fixed vertical plane from which all longitudinal arms are measured. It is defined by the manufacturer and may lie ahead of the nose, so arms can be positive or, occasionally, negative.

The product of an item's mass and its arm from the datum, expressed in mass-length units such as kg·m. Moments are summed and divided by total mass to locate the centre of gravity.

The forward and aft boundaries of centre of gravity position within which the aeroplane may be operated. They are expressed as a percentage of mean aerodynamic chord or as a distance from the datum, and vary with mass.

A centre of gravity near the forward limit increases the nose-down moment that the tailplane must counter, raising trim drag, lengthening the take-off run, and reducing climb performance and range.

A centre of gravity near the aft limit reduces tail downforce and trim drag, improving cruise efficiency, but it decreases longitudinal static stability and can make stall recovery and spin avoidance more difficult.

The maximum mass per unit area that a cargo compartment floor can carry. It is checked separately from total mass because a small, dense load can exceed it even when the aeroplane is well below maximum mass.

The document that records masses, CG position, and load distribution for a flight, signed by the person responsible. It confirms that take-off and landing masses and the CG lie within approved limits.

A change to load made after the load sheet is complete, such as added baggage or a passenger move. It must be recorded and assessed so that mass and CG limits remain satisfied before departure.

The altitude indicated when the altimeter subscale is set to 1013.25 hPa. Performance charts use it as the input altitude so that results are independent of local weather pressure.

Pressure altitude corrected for the difference between actual temperature and ISA temperature. High density altitude reduces air density, increasing take-off distance, reducing climb rate, and lowering available thrust or power.

A defined model of the atmosphere with sea-level temperature 15 °C, pressure 1013.25 hPa, and a lapse rate of 1.98 °C per 1000 ft up to the tropopause. Performance data are tabulated against ISA deviation.

The difference between the actual outside air temperature at a level and the ISA temperature for that level, quoted as ISA plus or minus a number of degrees. Positive deviation degrades most performance figures.

The length of the take-off run available plus any clearway. It limits the distance in which the aeroplane must reach 35 ft above the runway surface on a one-engine-inoperative or all-engines case as applicable.

The length of runway declared available and suitable for the ground run of an aeroplane taking off. It is the basic declared distance from which the other take-off distances are derived.

The length of the take-off run available plus any stopway. It bounds the distance needed to accelerate to a decision speed and then stop, and it is used to derive the balanced field length.

An area beyond the runway, at least 75 m wide, clear of obstacles and under the control of the aerodrome authority, over which an aeroplane may climb to 35 ft. It extends TODA but not TORA or ASDA.

A prepared rectangular area beyond the runway, at least as wide as the runway, suitable for an aeroplane to stop without structural damage. It extends ASDA but not TORA or TODA.

The field length at which the accelerate-stop distance equals the one-engine-inoperative take-off distance, so V1 can be chosen to satisfy both cases. It is the minimum field length for a given mass and condition.

The decision speed at which a failure is recognised and the take-off can still be stopped within the accelerate-stop distance, or continued to 35 ft within the take-off distance. It is chosen from the field length and obstacle data.

The rotation speed at which the pilot applies back pressure to raise the nose. It must be high enough for the aeroplane to reach V2 by 35 ft yet low enough to satisfy field length and tail-clearance limits.

The take-off safety speed to be attained by 35 ft above the runway with one engine inoperative and maintained to at least 400 ft. It guarantees a specified climb gradient and minimum control in the air.

The ratio of height gained to horizontal distance covered, usually expressed as a percentage. It is used with obstacle charts to confirm that the net flight path clears terrain after take-off or on approach.

The gross one-engine-inoperative climb path reduced by a defined gradient decrement, giving the conservative path used for obstacle clearance. The aeroplane must clear all obstacles by the required margin along this path.

The required vertical or horizontal separation between the net flight path and obstacles or terrain. It is checked against departure and approach charts and may limit take-off mass when obstacles are close to the runway.

The lowest of the structural, field-length, climb, and obstacle-limited masses for the actual conditions. It is the maximum mass at which the take-off may legally and safely be commenced.

The length of runway declared available and suitable for the ground run of a landing aeroplane. The required landing distance, factored for conditions, must not exceed it.

The lowest speed at which the aeroplane can maintain level flight in a given configuration, increasing with mass, load factor, and altitude. It sets the reference speeds and the low-speed end of the flight envelope.

The operator's defined method for calculating fuel, specifying taxi, trip, contingency, alternate, final reserve, and additional fuel. It ensures the flight can be completed and diverted with a protected reserve remaining.

The fuel needed from take-off to touchdown at the destination, including climb, cruise, descent, and approach. It is calculated for the planned route, mass, and forecast conditions.

Fuel added to cover unforeseen factors such as forecast error, routing changes, or mass differences. It is typically a percentage of trip fuel or a time allowance, chosen so that a diversion remains possible.

The fuel required to fly from the destination to the selected alternate aerodrome, including a missed approach and climb. It is carried when a destination alternate is required by the fuel policy.

The minimum fuel that must remain on arrival at the alternate or destination, usually expressed as 30 minutes of holding at 1500 ft above the aerodrome. It may not be planned for use except in an emergency.

An aerodrome to which a flight may proceed if a landing at the destination is not possible. Its selection depends on weather, runway suitability, and the fuel carried to reach it.

The document prepared for a flight that sets out route, altitudes, masses, fuel figures, times, and alternates. It is the basis for ATC filing and for in-flight fuel and diversion decisions.

The continuous comparison of fuel remaining against planned figures, with defined decision points for diverting or declaring a minimum fuel state. It ensures the final reserve is protected throughout the flight.

A declared state in which the fuel remaining is such that a landing at the intended aerodrome is expected with little margin above final reserve. It signals that further delay may require a diversion.

The distance flown per unit of fuel consumed, often expressed in nautical miles per kilogram. It peaks at a particular speed and altitude and is the basis for cruise and long-range fuel planning.