Jet Aircraft: Takeoff Performance Testing

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All obstacles in the takeoff flight path of an airplane must be cleared to a safe margin. Photo Credit: JoshuaDavisPhotography.

Obstacle Clearance

The third requirement for a jet’s takeoff performance is its ability to clear obstacles at a safe margin. In the event of an engine failure after decision speed, the pilot in command has enough distance to safely lift-off the ground and climb at a safe gradient.

However, the jet aircraft must also necessarily clear all obstacles in its takeoff flight path at a height that is at least 35ft measured vertically from the obstacle or at least 200ft horizontally from the obstacle (within airport boundaries).

Tire Speed and Brake Energy

A jet airplane’s tires attain maximum speed at lift-off. Limitations ensure that airplanes do not breach the tire’s rated speed, but in some cases take performance calculations determine that the maximum speed may be breached. In this case, operators reduce the weight of the aircraft, or flaps are used to lower the rotation speed.

The brake energy limitations on jet aircraft relate to the effectiveness of brakes after the absorption of a certain amount of energy. The amount of energy the brakes are exposed to increases with the increase in weight and decision speed. In order to decrease the energy the aircraft brakes are exposed to, the weight of the aircraft must be reduced or unbalanced.

These five aspects are taken into consideration while calculating the takeoff performance of a jet aircraft. For the same aircraft, these values change with the change in weather and weight. However, standard minimums are set by the ICAO to ensure safe flight for jet plane operations.

The takeoff of an Air China B-2471 (Boeing 747) from San Fransisco International Airport. Photo Credit: dsleeter_2000.

Resources:

Oxford Aviation Services. Joint Aviation Authorities Airline Transport Pilot’s License Theoretical Knowledge Manual. (2001). Accessed January 21, 2012.

Boeing. Takeoff Performance. (2009). Accessed January 21, 2012.

Federal Aviation Administration, Flight standards Service. Pilot’s Handbook of Aeronautical Knowledge. (2010). Accessed January 21, 2012.

Airbus. Flight Operations Briefing Notes. Accessed January 21, 2012.

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