Calculating Field Length Requirements for a Jet Takeoff


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Runway 010 at Carcassonne – Salvaza airport. Image Credit: Teeppix

The takeoff procedure of jet aircraft is governed by certain internationally-recognized and  standardized limitations that are there for the safety of the aircraft and the passengers therein. These standards are established by regulating authorities under the International Civil Aviation Organization.

This particular writeup focuses on terms and limitations associated with the field from which a jet plane takes off. Takeoff performance calculations require that field lengths used for takeoff must allow for at least one engine failure. Hence, for a jet to use any field for takeoff, the field length must be a value maximum of the following three.

All Engine Operation – Normal Takeoff for Jet Aircraft

During normal takeoff procedures, for a jet with all engines operational, the takeoff distance available must be at least 115% of the total horizontal length taken from takeoff-start point to screen height.

The screen height (35ft) is simply a requirement established by the authorities to be the minimum height at which a jet airplane should be, when it reaches the end of the runway.

One Engine Inoperative BEFORE Decision Speed

If an engine failure were to occur before the airplane reaches its decision speed (V1), the pilot in command has the advantage of stopping the aircraft. However, the field being used must be of considerable length to allow the momentum of the aircraft to die out and hence stop. The distance calculated to cater for such an instance is called the accelerate stop distance (ASD).

The total horizontal distance required to accelerate to decision speed, apply braking without reverse thrust, and bring the airplane to a stop, is called the accelerate stop distance.

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