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The Fokker 100 aircraft incorporates a safety system to deal with an accidental deployment of a thrust reverser on take-off or when in flight; the system automatically moves the thrust control of the affected Rolls-Royce Tay 650-15 engine to reduce power, the aeroplane then being capable of climbing out safely on the full power of the one unaffected engine, or of maintaining normal flight at reduced power. In addition, a micro-switch, activated by the aircraft's main landing gear leaving the ground, disables the thrust reverser operating circuitry, preventing inadvertent operation of the thrust reverser in flight.


As the aircraft lifted off the runway on the accident flight with both engines at full power, a faulty switch in conjunction with a possible short circuit caused the right engine's thrust reverser to deploy. The imb
alance of power resulted in the aircraft rolling and veering to the right as it was climbing away from the runway. The safety system automatically cut the power to the engine with the malfunctioning thrust reverser. There was no alarm or other indication in the cockpit to indicate that a thrust reverser had been accidentally deployed. The crew had no way of knowing what the true problem was. The copilot, seeing the right engine power lever automatically move to the closed position, thought that the lever had slipped back due to a problem with the autothrottle system and pushed it back to the full power position alongside the left engine throttle lever. Once again, the automatic safety system closed the right engine throttle and the captain, who was conducting the takeoff, called for the autothrottle system to be switched off. After switching off the system, the copilot again pushed the right engine power lever fully forward and forcefully held it there.

The safety system cable, responsible for pulling the power lever to the idle position, was no longer able to withstand the physical strain of being pulled one way by the actuator, while the copilot forced it the other way by pushing the throttle lever to the fully open position — the cable soon parted at a maintenance connection. With the lever no longer restrained by the safety system, the copilot continued to hold the right throttle fully open. The combination of the right engine at full thrust in reverse and the left engine still at normal forward take-off thrust caused the aircraft to roll violently to the right and descend into the ground.[1]

Source:Wikipedia