Aircraft Dispatcher key terms

A service that directs aircraft on the ground and in the air, issuing clearances and separating traffic so that collisions are prevented and the flow of flights stays orderly and efficient.

Reduced Vertical Separation Minimum: rules and aircraft equipment standards that permit 1,000-foot vertical spacing between approved aircraft above a specified altitude, typically flight level 290, instead of the usual 2,000 feet.

VHF Omnidirectional Range: a ground navigation beacon that broadcasts signals allowing an aircraft to determine its bearing to the station; crews track radials to or from it for en-route navigation.

A published, charted procedure that links a runway to the en-route structure, giving headings, altitudes and speeds that keep departing traffic clear of obstacles and separated from other aircraft.

A racetrack-shaped flight path flown at an assigned fix, direction, altitude and leg time while awaiting further clearance; it keeps the aircraft inside protected airspace and predictable for controllers.

The lowest height on an instrument approach with vertical guidance at which the crew must see the required visual references or fly a missed approach; approaches without vertical guidance use a minimum descent altitude instead.

A routine coded observation of surface weather at an airport, usually issued hourly, reporting wind, visibility, cloud layers, temperature, dew point, pressure and significant weather phenomena.

A coded forecast of expected weather at or near an airport, covering wind, visibility, clouds and phenomena over a stated period; it is used to plan departures, arrivals and alternate requirements.

Significant Meteorological Information: a warning of hazardous weather such as severe turbulence, icing, thunderstorms, volcanic ash or tropical cyclones that may affect flight safety along a route.

A rapid change of wind speed or direction over a short distance, either horizontally or vertically; shear close to the ground on approach or departure can cause sudden airspeed loss.

The height above ground of the lowest broken or overcast cloud layer; it is a primary factor in deciding whether visual conditions exist and which approach minimums apply.

The altitude at which air temperature reaches zero degrees Celsius; above it, visible moisture can freeze on airframe surfaces and engine intakes, reducing lift and available power.

Pilot Report: an observation relayed by flight crew describing actual conditions aloft, such as turbulence, icing, wind and cloud tops, which supplements and validates forecasts for other flights.

Pressure altitude corrected for non-standard temperature. High density altitude thins the air, reducing engine power, thrust and lift, which lengthens takeoff and landing runs and weakens climb performance.

The takeoff decision speed: if an engine fails before reaching it, the aircraft can still be stopped on the remaining runway; after it, the takeoff should be continued.

The highest altitude at which an aircraft can still climb at a specified minimum rate, commonly 100 feet per minute; above this level the climb capability is effectively unusable.

The runway length at which the distance needed to continue a takeoff after an engine failure equals the distance needed to abort and stop, giving the minimum acceptable field for a given weight.

A runway covered by standing water, slush, snow or ice. The covering reduces braking friction and adds drag, increasing stopping distance and lowering the maximum weight allowed for takeoff or landing.

The heaviest weight at which an aircraft is certified to touch down, set by structural limits of the gear and airframe; excess fuel may have to be burned off or jettisoned before landing.

The empty weight of the aircraft plus required crew, their baggage, crew supplies and unusable or trapped fluids; payload and usable fuel are added to this figure to obtain takeoff weight.

The forward and aft range of center-of-gravity positions within which an aircraft is certified to operate; outside these limits stability, control forces and performance may become unacceptable.

The aircraft weight including crew, passengers, baggage and cargo but excluding usable fuel; as a structural limit it caps payload before fuel is added.

The document prepared before departure that shows how weight is distributed through the aircraft, the resulting center of gravity, and confirmation that all limits are satisfied.

An airport named in the flight plan to which a flight may proceed if landing at the intended destination becomes impractical or impossible because of weather, runway closure or other reasons.

A point along the route where the flying time to either of two diversion airports is the same; it supports fuel planning and diversion decisions on long overwater or remote segments.

Notice to Air Missions: a message distributed to crews and dispatchers about temporary changes or hazards, such as closed runways, unserviceable navigation aids, or new obstacles and restrictions.

Fuel carried to cover unforeseen factors such as weather deviations, traffic delays or routing changes; it is often a percentage of trip fuel or a set time and is separate from reserve fuel.

Fuel that must still be in the tanks on arrival at the destination, typically enough for a missed approach, a flight to the alternate and holding; it is not planned for routine use.

Carrying more fuel than the trip requires from a departure airport so that less must be purchased where fuel is more expensive, weighed against the extra fuel burned carrying the added weight.

Extended diversion time operations: rules that let twin-engine aircraft fly routes far from an adequate airport, provided specified system reliability, fuel and diversion-time criteria are met.

The document and joint decision by which a certificated dispatcher and the pilot in command authorize a flight, stating routing, fuel, weather, alternates and operational limits.

An approved document allowing a flight to depart with specific items of equipment inoperative, subject to stated conditions, maintenance actions and operating restrictions.

The authority-issued document defining an operator's authorized routes, airports, equipment, procedures and limitations; flights must be conducted within what it permits.

Rules capping how many hours crew members may fly and remain on duty within given periods, with required rest, in order to limit fatigue-related errors.

A procedure used after an engine failure or loss of pressurization at high altitude in which the aircraft descends to a lower level it can maintain on remaining power, used to plan escape routes over terrain.

Training and practices that help crews use all available people, information and equipment effectively, emphasizing communication, leadership, workload sharing and error management.

An accident in which an airworthy aircraft is flown into ground, water or an obstacle without the crew being aware of the impending impact; terrain awareness systems and stabilized approaches are key defenses.

A rapid descent, often to a lower altitude after loss of cabin pressure, flown at maximum safe speed with the crew on oxygen while following published procedures and alerting air traffic control.