Jet Aircraft: Takeoff Performance Testing

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Jet planes must maintain a minimum climb gradient after lift-off, deemed safe by the regulating authorities. Photo Credit: Roo Reynolds.

After a jet aircraft is manufactured, it goes through a series of tests that check its performance, including measures of its takeoff abilities. These tests attempt to predict and standardize the minimum acceptable behavior of a jet airplane, to reduce problems that occur in the event of an emergency.

The expected behavior of the plane will, of course, change with the variation in the make, size and model of the airplane under consideration. Nonetheless, five basic requirements are taken into account while evaluating a jet plane’s takeoff performance. These five  areas are: required field length, climb capability, obstacle clearance, tire speed, and brake energy.

The Effect of Field Length on Jet Airplanes

To takeoff safely, a jet requires a minimum field length that enables it to build up speed and hence takeoff at a safe speed. This minimum field length is required for the following reasons:

  • A minimum field length ensures that the jet takes off safely during all-engine operation.
  • Jet aircraft must have a reasonable distance available to stop, if takeoff is aborted before decision speed is reached.
  • Jet planes must have a reasonable distance available to safely lift-off, if an event has occurred after decision speed is reached.

Calculate relevant speeds with respect to the weight of the airplane, meteorological conditions and usable runway length available, to evaluate these factors for individual aircraft.

Climb Requirements

The climb requirements for jet planes, with respect to their takeoff performance, ensure that in the event of a take-off with one engine inoperative, the airplane can still climb up to a minimum of 15ooft at a climb gradient deemed safe by the regulating authorities.

The takeoff flight path a jet follows to climb up to 1500ft is divided into four segments. Of these four segments, the climb requirement for the second segment is the most critical and limiting portion. In order to achieve the minimum set climb gradient, the aircraft’s weight must be kept under check.

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