| Absolute Ceiling | The altitude at which the theoretical rate of climb, with all engines operating at maximum continuous power, is reduced to zero feet per minute. |
| ASDA: Accelerate-stop Distance Available | The distance from the point on the surface of the aerodrome at which the aeroplane can commence its take-off run to the nearest point in the direction of take-off at which the aeroplane cannot roll over the surface of the aerodrome and be brought to rest in an emergency without the risk of accident. It is equal to TORA plus any available Stopway. |
| Aerodrome | Any area of land or water designed, equipped, set apart or commonly used for affording facilities for the landing and departure of aircraft and includes any area or space, whether on the ground, on the roof of a building or elsewhere, which is designed, equipped or set apart for affording facilities for the landing and departure of aircraft capable of descending or climbing vertically, but shall not include any area the use of which for affording facilities for the landing and departure of aircraft has been abandoned and has not been resumed. |
| Aerodrome Elevation | The elevation of the highest point of the landing area. |
| Aerodrome Reference Point | The aerodrome reference point is the geographical location of the aerodrome and the centre of its traffic zone where an ATZ is established. |
| Aerodynamic Ceiling | The altitude, in unaccelerated 1g level flight, where the Mach number for the low speed and high-speed buffet are coincident. |
| Aeroplane | A power-driven heavier-than-air aircraft, deriving its lift in flight chiefly from aerodynamic reactions on surfaces which remain fixed under given conditions of flight. |
| Aircraft | A machine that can derive support in the atmosphere from the reactions of the air other than the reactions of the air against the earth’s surface. |
| Aircraft Classification Number (ACN) | This is a value assigned to an aeroplane to show its load force. The aircraft classification number must be compared to the pavement classification number (PCN) of an aerodrome. The aircraft classification number may exceed the pavement classification number by as much as 50% but only if the manoeuvring of the aeroplane is very carefully monitored, otherwise significant damage may occur to both the aeroplane and the pavement. ACN < PCN |
| Airframe | The fuselage, booms, nacelles, cowlings, fairings, aerofoil surfaces (including rotors but excluding propellers and rotating aerofoils of engines), and landing gear of an aircraft and their accessories and controls. |
| VMCA -Air Minimum Control Speed | The minimum speed at which directional control can be demonstrated when airborne with the critical engine inoperative and the remaining engines at take-off thrust. Full opposite rudder and not more than 5 degrees of bank away from the inoperative engine are permitted when establishing this speed. VMCA may not exceed 1.2VS1 or 1.13VSR. |
| Alternate Airport | An airport at which an aircraft may land if a landing at the intended airport becomes inadvisable. |
| Altitude | The altitude shown on the charts is pressure altitude. This is the height in the International Standard Atmosphere at which the prevailing pressure occurs. It may be obtained by setting the subscale of a pressure altimeter to 1013 hPa. |
| Angle of Attack | The angle between the chord line of the wing of an aircraft and the relative airflow. |
| Apron | A defined area on a land aerodrome provided for the stationing of aircraft for the embarkation and disembarkation of passengers, the loading and unloading of cargo, and for parking. |
| Auxiliary Power Unit | Any gas turbine-powered unit delivering rotating shaft power, compressor air, or both which is not intended for direct propulsion of an aircraft. |
| Balanced Field | A runway for which the Accelerate-stop Distance Available is equal to the Take-off Distance Available is considered to have a balanced field length. ASDA = TODA |
| Baulked Landing | A landing manoeuvre that is unexpectedly discontinued. |
| Brake Horsepower | The power delivered at the main output shaft of an aircraft engine. |
| Buffet Speed | The speed at which the airflow over the wing separates creating turbulent airflow aft of the separation point which buffets the aeroplane. |
| CAS -Calibrated Airspeed | The indicated airspeed, corrected for position and instrument error. It is equal to True Airspeed (TAS) at Mean Sea Level (MSL) in a Standard Atmosphere. |
| Climb Gradient | The ratio, in the same units of measurement, expressed as a percentage, as obtained from the formula: – Climb gradient=H/R×100 |
| Clearway | An area beyond the runway, not less than 152 m (500 ft) wide, centrally located about the extended centre line of the runway, and under the control of the airport authorities. The clearway is expressed in terms of a clearway plane, extending from the end of the runway with an upward slope not exceeding +1·25%, above which no object or terrain protrudes. However, threshold lights may protrude above the plane if their height above the end of the runway is 0·66 m (26 inches) or less and if they are located to each side of the runway. |
| Cloud Ceiling | In relation to an aerodrome, cloud ceiling means the vertical distance from the elevation of the aerodrome to the lowest part of any cloud visible from the aerodrome which is sufficient to obscure more than one half of the sky so visible. |
| Contaminated Runway | A runway is contaminated when more than 25% of the runway surface area is covered by surface water, more than 3 mm deep. |
| Continuous One Engine Inoperative Power Rating | The minimum test bed acceptance power, as stated in the engine type certificate data sheet, when running at the specified conditions and within the appropriate acceptance limitations. |
| Continuous One Engine Inoperative Thrust Rating | The minimum test bed acceptance thrust, as stated in the engine type certificate data sheet, when running at the specified conditions and within the appropriate acceptance limitations. |
| Continuous One Engine Inoperative Power | The power identified in the performance data for use after take-off when a power unit has failed or been shut down, during periods of unrestricted duration. |
| Continuous One Engine Inoperative Thrust | the thrust identified in the performance data for use after take-off when a power unit has failed or been shut down, during periods of unrestricted duration. |
| Critical Engine | The engine whose failure would most adversely affect the performance or handling qualities of an aircraft. |
| Damp Runway | A runway is considered damp when the surface is not dry, but when the moisture on it does not give it a shiny appearance. |
| Declared Distances | The distances declared by the aerodrome authority for the purpose of application of the requirement of the Air Navigation Order. |
| V1-Decision Speed | The maximum speed in the take-off at which the pilot can take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the aeroplane within the accelerate-stop distance. It also means the minimum speed in the take-off, following a failure of the critical engine at VEF at which the pilot can continue the take-off and achieve the required height above the take-off surface within the take-off distance. |
| Density Altitude | The altitude in ISA, where the prevailing measured density occurs. |
| Drag | That force on an aeroplane which directly opposes thrust. |
| Dry Runway | A dry runway is one which is neither wet nor contaminated and includes those paved runways which have been specially prepared with grooves or porous pavement and maintained to retain ‘effectively dry’ braking action even when moisture is present. |
| Elevation | The vertical distance of an object above mean sea level. This may be given in meters or feet. |
| En Route | The en route phase extends from 1500 ft above the take-off surface level to 1000 ft above the landing aerodrome surface level for Class B aeroplane or to 1500 ft above the landing aerodrome surface level for Class A aeroplane. |
| EAS-Equivalent Airspeed | The calibrated airspeed corrected for compressibility at the particular pressure altitude under consideration. It is equal to Calibrated Airspeed in a Standard Atmosphere. |
| EGT -Exhaust Gas Temperature | The average temperature of the exhaust gas stream. |
| Final En Route Climb Speed | The speed of the aeroplane in segment four of the take-off flight path with one engine inoperative. |
| Final Segment Speed | The speed of the aeroplane in segment four of the take-off flight path with one engine inoperative. |
| Final Take-off Speed | The speed of the aeroplane that exists at the end of the take-off path in the en route configuration with one engine inoperative. |
| Fixed Pitch Propeller | A propeller, the pitch of which cannot be changed. |
| VFE- Flap Extended Speed | The highest speed permissible with wing flaps in a prescribed extended position. |
| Flight Level | A surface of constant atmospheric pressure that is related to 1013.25 hPa. It is conventionally the pressure altitude to the nearest 1000 ft in units of 100 ft. For example, flight level 250 represents a pressure altitude of 25 000 ft. |
| Frangibility | The ability of an object to retain its structural integrity and stiffness up to a specified maximum load but when subject to a load greater than specified or struck by an aircraft will break, distort or yield in such a manner as to present minimum hazard to an aircraft. |
| Go-around | A procedure involving a decision to abort the landing and climb straight ahead to rejoin the circuit. Such a decision might be taken at any time during the final approach, the transition phase or even after initial touchdown. |
| Gross Height | The true height attained at any point in the take-off flight path using gross climb performance. Gross height is used for calculating pressure altitudes for purposes of obstacle clearance and the height at which wing flap retraction is initiated. |
| Gross Performance | The average performance that a fleet of aeroplane should achieve if satisfactorily maintained and flown in accordance with the techniques described in the manual. |
| VMCG: Ground Minimum Control Speed | The minimum speed at which the aeroplane can be demonstrated to be controlled on the ground using only the primary flight controls when the most critical engine is suddenly made inoperative, and the remaining engines are at take-off thrust. Throttling an opposite engine is not allowed in this demonstration. Forward pressure from the elevators is allowed to hold the nose wheel on the runway, however, nose wheel steering is not allowed. You can use rudder to arrest the YAW and elevator to keep nose wheel on the ground. |
| Height | The vertical distance between the lowest part of the aeroplane and the relevant datum. |
| Hydroplaning Speed | The speed at which the wheel is held off the runway by a depth of water and directional control through the wheel is impossible. |
| ICAO Standard Atmosphere | The atmosphere is defined in ICAO Document 7488/2. For the purposes of Certification Specifications, the following are acceptable: The air is a perfect dry gas. The temperature at sea level is 15°C. The pressure at sea level is 1013.2 hPa (29.92 in Hg) The temperature gradient from sea level to the altitude at which the temperature becomes –56.5°C is 0.65°C/100 m (1.98°C/1000 ft) The density at sea level under the above conditions is 1.2250 kg/m3. |
| IFR Conditions | Weather conditions below the minimum for flight under visual flight rules. |
| IAS -Indicated Airspeed | The speed as shown by the pitot/static airspeed indicator calibrated to reflect Standard Atmosphere adiabatic compressible flow at MSL and uncorrected for airspeed system errors. |
| Instrument | A device using an internal mechanism to show visually or aurally the attitude, altitude, or operation of an aircraft or aircraft part. It includes electronic devices for automatically controlling an aircraft in flight. |
| LDA-Landing Distance Available | The distance from the point on the surface of the aerodrome above which the aeroplane can commence its landing, having regard to the obstructions in its approach path, to the nearest point in the direction of landing at which the surface of the aerodrome is incapable of bearing the weight of the aeroplane under normal operating conditions or at which there is an obstacle capable of affecting the safety of the aeroplane. |
| VLE-Landing Gear Extended Speed | The maximum speed at which an aircraft can be safely flown with the landing gear extended. |
| VLO-Landing Gear Operating Speed | The maximum speed at which the landing gear can be safely extended or retracted. |
| Landing Minimum Control Speed | The minimum speed with a wing engine inoperative where it is possible to decrease thrust to idle or increase thrust to maximum take-off without encountering dangerous flight characteristics. |
| Large Aeroplane | An aeroplane of more than 5700 kg maximum certificated take-off weight. The category ‘Large Aeroplane’ does not include the commuter aeroplane category. |
| Lift | That force acting on an aerofoil which is at right angles to the direction of the airflow. |
| Load Factor | The ratio of a specified load to the total weight of the aircraft. The specified load is expressed in terms of any of the following: aerodynamic forces, inertia forces, or ground or water reactions. |
| Mach Number | The ratio of true airspeed to the Local Speed of Sound (LSS). |
| Manoeuvre Ceiling | The pressure altitude provides a 0.3 g margin to both the high-speed buffet and the low-speed buffet. |
| VMBE-Maximum Brake Energy Speed | The maximum speed on the ground from which an aeroplane can safely stop within the energy capabilities of the brakes. |
| Maximum Continuous Power | The power identified in the performance data for use during periods of unrestricted duration. |
| MCT-Maximum Continuous Thrust | The thrust identified in the performance data for use during periods of unrestricted duration. |
| MSTOM- Maximum Structural Take-off Mass | The maximum permissible total mass of an aeroplane at the start of the take-off run. |
| Maximum Structural Landing Mass | The maximum permissible total mass of an aeroplane on landing (under normal circumstances). |
| VMC-Minimum Control Speed | The minimum speed at which the aeroplane is directionally controllable with the critical engine inoperative and the remaining engines at take-off thrust. |
| VMU-Minimum Unstick Speed | The minimum speed demonstrated for each combination of weight, thrust, and configuration at which a safe take-off has been demonstrated. |
| Missed Approach | When an aircraft is caused to abort a landing after it has already started its landing approach. The aircraft has to follow a set missed approach procedure to leave the airspace surrounding the terminal. |
| Net Height | The true height attained at any point in the take-off flight path using net climb performance. Net height is used to determine the net flight path that must clear all obstacles by the statutory minimum to comply with the Operating Regulations. |
| Net Performance | Net performance is the gross performance diminished to allow for various contingencies that cannot be accounted for operationally e.g. variations in piloting technique, temporary below average performance, etc. It is improbable that the net performance will not be achieved in operation, provided the aeroplane is flown in accordance with the recommended techniques. |
| Outside Air Temperature | The free air static (ambient) temperature. |
| Pitch Setting | The propeller blade setting determined by the blade angle, measured in a manner and at a radius declared by the manufacturer and specified in the appropriate Engine Manual. |
| Pitch | Motion of the aeroplane about its lateral axis. |
| Pitot Tube | A small tube whose open end collects Total Pressure. |
| Pressure Altitude | The altitude of an aircraft above the pressure level of 1013.25 hPa. This is achieved by setting the altimeter subscale to 1013 hPa and reading the altitude indicated. |
| VSR-Reference Landing Speed | The speed of the aeroplane, in a specified landing configuration, at the point where it descends through the landing screen height in the determination of the landing distance for manual landings. |
| Rejected Take-off (RTO) | A situation or event in which it is decided, for safety reasons, to abandon the take-off of an aircraft. |
| Roll | Motion of the aeroplane about its longitudinal axis. |
| VR-Rotation Speed | The speed at which, during the take-off, rotation is initiated with the intention of becoming airborne. Pull AFT to rotate the airplane. |
| Runway | A defined rectangular area on a land aerodrome prepared for the landing and take-off run of aircraft along its length. |
| Runway Strip | An area of specified dimensions enclosing a runway intended to reduce the risk of damage to an aircraft running off the runway and to protect aircraft flying over it when taking off or landing. |
| Runway Threshold | The beginning of that portion of the runway usable for landing. |
| Screen | An imaginary barrier, located at the end of the Take-off Distance Available (TODA) or the beginning of the Landing Distance Available (LDA). The screen is of no operational significance, but the test pilots use the height of the screen when assessing the performance of the aeroplane. |
| Service Ceiling | The pressure altitude at which the rate of climb is reduced to a specified minimum value (approximately 300 ft/min). |
| Specific Fuel Consumption | Fuel flow per unit thrust. The lower the value, the more efficient the engine. |
| Stopway | An area beyond the take-off runway, no less wide than the runway and centered upon the extended centre line of the runway, able to support the aeroplane during an aborted take-off, without causing structural damage to the aeroplane, and designated by the airport authorities for use in decelerating the aeroplane during an aborted take-off. |
| TODA-Take-off Distance Available | It is equal to TORA plus any clearway and cannot be more than one- and one-half times the TORA, whichever is the less. |
| Take-off Mass | The mass of an aeroplane, including everything and everyone contained within it, at the start of the take-off run. |
| Take-off Power | The output shaft power identified in the performance data for use during take-off, discontinued approach, and baulked landing: for piston engines, it is limited in use to a continuous period of not more than 5 minutes. for turbine engines installed in airplanes and helicopters, limited in use to a continuous period of not more than 5 minutes; and for turbine engines installed in aeroplanes only (when specifically requested), limited in use to a continuous period of not more than 10 minutes in the event of a power unit having failed or been shut down. |
| TORA-Take-off Run Available | The distance from the point on the surface of the aerodrome at which the aeroplane can commence its take-off run to the nearest point in the direction of take-off at which the surface of the aerodrome is incapable of bearing the weight of the aeroplane under normal operating conditions. |
| TOSS- V2-Take-off Safety Speed | A referenced airspeed obtained after lift-off at which the required one engine-inoperative climb performance can be achieved. V2 is more than V1 and the VS- includes a safety margin. |
| Take-off Thrust | the output shaft thrust identified in the performance data for use during take-off, discontinued approach, and baulked landing: for piston engines, it is limited in use to a continuous period of not more than 5 minutes. for turbine engines installed in aeroplanes and helicopters, limited in use to a continuous period of not more than 5 minutes; and for turbine engines installed in aeroplane only, limited in use to a continuous period of not more than 10 minutes in the event of a power unit having failed or been shut down. |
| Taxiway | A defined path on a land aerodrome established for the taxiing of aircraft and intended to provide a link between one part of the aerodrome and another. |
| Thrust | That force acting on an aeroplane produced by the engine(s) in a forward direction. |
| True Airspeed | The airspeed of an aircraft relative to undisturbed air. |
| Turbojet | An aircraft having a jet engine in which the energy of the jet operates a turbine that in turn operates the air compressor. |
| Turboprop | An aircraft having a jet engine in which the energy of the jet operates a turbine that drives the propeller. Turboprops are often used on regional and business aircraft because of their relative efficiency at speeds slower than, and altitudes lower than, those of a typical jet. |
| Variable Pitch Propellers | A propeller, the pitch setting of which changes or can be changed, when the propeller is rotating or stationary. |
| VEF – engine failure speed | one second earlier than V1. The calibrated airspeed at which the critical engine is assumed to fail and is used for the purpose of performance calculations. It is never less than VMCG. If the engine fails at VEF or less – you will be able to execute all the action till V1. |
| V1- takeoff decision speed | Referred to as the decision speed. Engine failure prior to V1 demands that the pilot must reject the take-off because there is insufficient distance remaining to enable the aircraft to safely continue the take-off. Engine failure at or faster than V1 demands that the pilot must continue the take-off because there is insufficient distance remaining to safely bring the aircraft to a stop. |
| Wet Runway | A runway is considered wet when the runway surface is covered with water, or equivalent moisture on the runway surface to cause it to appear reflective, but without significant areas of standing water. |
| Windshear | Localized change in wind speed and/or direction over a short distance, resulting in a tearing or shearing effect that can cause a sudden change of airspeed with occasionally disastrous results if encountered when taking off or landing. |
| Yaw | Motion of an aeroplane about its normal axis. |
| Zero Flap Speed | The minimum safe maneuvering speed with zero flap selected. |
