NCAA PPL Flight Performance & Planning key terms

The heaviest mass an aircraft is certified to have at the start of the takeoff run, set by the manufacturer and stated in the flight manual. It may be limited further by runway, obstacle, or climb performance on a given day.

The heaviest mass at which the aircraft is certified to touch down, protecting the landing gear and structure. A flight planned above this figure must either burn or jettison fuel before landing or reduce payload.

The heaviest mass permitted before usable fuel is added. It caps the combined load of structure, crew, passengers, baggage, and cargo, and is often the limiting factor on short flights with full tanks.

The actual mass of the aircraft with crew, passengers, baggage, cargo, and unusable fuel but no usable fuel. It is calculated as basic empty mass plus traffic load and compared against the maximum zero fuel mass.

The mass of the empty aircraft including unusable fuel, full engine oil, and all equipment required for certification. It is recorded in the mass and balance report and is the starting point for every loading calculation.

Basic empty mass plus crew, crew baggage, catering, potable water, and other operational items. It represents the aircraft ready for a flight except for traffic load and usable fuel.

The total mass of passengers, baggage, cargo, and any non-operational items carried for revenue or company purposes. It is added to dry operating mass to give zero fuel mass.

The difference between maximum takeoff mass and basic empty mass, being everything the aircraft can carry: crew, fuel, passengers, and cargo. It is a rough capacity indicator rather than a legal limit.

The mass of revenue-earning traffic, meaning passengers, baggage, and cargo, sometimes including mail. It is what remains after fuel and operational items are subtracted from the allowed takeoff mass.

A published average mass per passenger, including hand baggage, used when actual weights are not taken. Operators may use it only where the authority permits and must add an allowance for small children and infants.

The point through which the total weight of the aircraft acts. Its position along the longitudinal axis is expressed as a distance from the reference datum and must stay inside the certified forward and aft limits.

An imaginary vertical plane from which all longitudinal distances used in balance calculations are measured. It is fixed by the manufacturer and may lie ahead of the nose, so some arms can be negative.

The horizontal distance from the reference datum to the point where a mass is applied. Multiplying a mass by its arm gives a moment, and summing moments locates the centre of gravity.

The product of a mass and its moment arm, expressed in kilogram-metres or pound-inches. Moments are summed and divided by total mass to find the centre of gravity position.

The forward and aft boundaries, and sometimes a maximum mass-dependent envelope, within which the centre of gravity must remain for all phases of flight. Exceeding them can degrade control, performance, and structural safety.

The most forward permitted centre of gravity position, set by elevator authority for rotation and landing flare. An excessively forward CG raises stall speed and takeoff distance and may prevent rotation.

The most rearward permitted centre of gravity position, set by stability and stall recovery requirements. An excessively aft CG reduces static margin and can make the aircraft unstable or unrecoverable in a stall.

A worksheet listing masses, arms, and moments for each load item so that total mass and CG can be computed. It also shows limits and is signed by the person responsible before dispatch.

The document recording basic empty mass, its CG, and the equipment installed, used as the baseline for loading. It must be updated when equipment changes and is carried or available on the flight.

A late alteration to the load after the load sheet is complete, such as a passenger moved or baggage added. It must be assessed for both mass and CG effect and recorded using approved procedures.

The runway length needed to accelerate, lose an engine at the critical point, and either continue to a specified height or stop. It must not exceed the takeoff distance available.

The length of the takeoff run available plus any clearway declared for the runway. It is the certified limit against which the takeoff distance required is compared.

The length of runway declared available and suitable for the ground run of an aircraft taking off. It is the primary runway dimension quoted in aerodrome documentation and used in performance charts.

The takeoff run available plus any stopway, being the distance in which an aircraft can be brought to a stop after a rejected takeoff. It bounds the accelerate-stop distance required.

An area beyond the runway end, under the control of the aerodrome authority, free of obstacles and suitable for an aircraft to climb over to a specified height. It extends takeoff distance available but not the run.

A prepared rectangular area beyond the runway end, able to support an aircraft without structural damage during a rejected takeoff. It adds to accelerate-stop distance available but is not used for normal takeoff.

The decision speed at which, after an engine failure, the takeoff can still be safely continued or rejected within the remaining runway. It is chosen so both outcomes are possible and is stated before departure.

The speed at which the pilot initiates rotation to the takeoff attitude, allowing the aircraft to lift off at the correct speed. It is derived from performance data and must not be below the minimum control speed.

The minimum speed to be maintained after an engine failure during the takeoff climb, giving required climb gradient and control. It must be reached by the screen height and held to the acceleration altitude.

The runway length at which the accelerate-stop distance and the continued takeoff distance with one engine failed are equal. It gives the shortest field for a given mass and is used to set V1.

The ratio of height gained to horizontal distance covered, usually expressed as a percentage. Required gradients for each segment of the takeoff and approach climb are fixed by certification rules and depend on aircraft configuration.

The pressure altitude corrected for temperature deviation from the standard atmosphere. High density altitude reduces engine power, propeller or fan thrust, and lift, lengthening takeoff and landing distances.

The altitude indicated when the altimeter subscale is set to the standard pressure of 1013.25 hPa or 29.92 inHg. It is the input to most performance charts, together with temperature and mass.

The runway length needed to land from a specified height over the threshold, touch down, and stop, including any regulatory factor. It must not exceed the landing distance available.

The length of runway declared available and suitable for the ground run of a landing aircraft. It may be shorter than the takeoff run available where the threshold is displaced.

A threshold moved down the runway from the physical end, usually for obstacle clearance or noise. The portion behind it is not available for landing but may be used for takeoff and for taxiing.

The operator's approved rules for calculating fuel, covering taxi, trip, contingency, alternate, final reserve, and additional fuel. It sets the minimum acceptable fuel at departure and the in-flight re-planning conditions.

Fuel carried to cover unforeseen factors such as deviations from forecast wind, routing, or cruise level. It is normally a percentage of trip fuel or a fixed time, chosen according to the approved fuel policy.

The minimum fuel that must remain on arrival at the destination or alternate, intended for holding. It is a fixed time at holding speed and must never be planned to be used except in an emergency.

Fuel needed to fly from a missed approach at the destination to the alternate aerodrome, climb, approach, and land. It is required only when an alternate is nominated under the fuel and weather rules.

Fuel consumed from takeoff to touchdown at the destination, including climb, cruise, descent, and approach. It is computed from the planned route, mass, level, and forecast temperatures and winds.

The distance an aircraft can fly per unit of fuel, typically nautical miles per kilogram or per pound. It peaks at a particular speed and altitude and is used to compare cruise efficiency.

The cruise level at which the aircraft achieves its best specific range for the current mass and temperature. As fuel burns off, the optimum altitude rises, which is why long flights step-climb.

A planned increase in cruise level during a flight as mass decreases, keeping the aircraft near its optimum altitude. Each step must be cleared by air traffic control and checked for terrain and traffic separation.

A number entered into the flight management system that balances fuel cost against time cost when selecting cruise speed. A low value favours economy, a high value favours speed.

The document filed with air traffic services describing route, levels, times, and aircraft details for a proposed flight. It also supports search and rescue alerting and must be amended if the flight changes materially.

The operator's working document giving route, masses, fuel, times, and alternates for a specific flight. It is prepared by flight dispatch, checked and signed by the commander, and retained for the required period.

An aerodrome to which a flight may proceed if an approach at the destination cannot be completed. It must be nominated when weather or fuel rules require and must meet availability and approach criteria.

A surface of constant pressure shown on the altimeter when set to standard pressure, expressed in hundreds of feet. Levels are assigned by air traffic control and separated by a prescribed interval.

The altimeter subscale setting that makes the instrument read aerodrome elevation when on the ground. It is used below the transition altitude and is updated from reported pressure during flight.

The altitude at or below which the altimeter is set to local pressure and above which standard pressure is used. Its value varies by country and is published on charts and in the flight plan.

The approved document, sometimes called a loading manual, giving arms, limits, and procedures for computing mass and CG. It is part of the operating documentation and must match the aircraft's configuration.

The manufacturer's approved document containing limitations, procedures, and performance data for the specific aircraft. It is legally binding and its data take precedence over other sources when they conflict.

The certified limits on masses, speeds, altitudes, temperatures, and configuration within which the aircraft may be operated. They are listed in the flight manual and must be respected in planning and in flight.

A document, separate from or part of the flight manual, containing takeoff, climb, cruise, and landing data in chart or table form. It states the assumptions and corrections needed for actual conditions.

A cleared area beyond the runway end intended to reduce damage if an aircraft overruns or undershoots. Its dimensions are set by the aerodrome authority and it is not counted in declared distances.

The vertical or horizontal margin kept between an aircraft's flight path and terrain, buildings, or other obstacles. Performance planning checks that the net flight path clears all obstacles by the required margin.

Loss of thrust from one power unit, which drives the certification cases for takeoff, climb, and drift-down planning. Performance data assume the critical engine fails at the worst point.

The initial tendency of an aircraft to return to its trimmed state after a small disturbance. It decreases as the centre of gravity moves aft, which is why the aft limit is a safety boundary.

The deliberate pitch-up at the rotation speed that raises the nose and increases lift for liftoff. Too forward a centre of gravity can make rotation difficult or impossible within the available runway.