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Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust for it to act against the forward travel of the aircraft, providing deceleration. Thrust reverser systems are featured on many jet aircraft to help slow down just after touch-down, reducing wear on the brakes and enabling shorter landing ...
The reverse-thrust ratio (ratio of backward engine thrust to forward reverse thrust) can be as high as 84%. [6] However, this result is obtained with a cowl to attach air flow in a 7° angle and a large enough "target" (deflector door) installed. A reverse-thrust ratio of 55% can be reached on a simple target without the cowl. [7]
To avoid a fatal collision, Miles immediately disengaged reverse thrust and both pilots slammed the throttle levers all the way forward and pulled back on their control columns to abort the 737's landing and initiate a go-around. They pushed so hard on the throttles that Miles fractured his thumb. [6]
The equivalent concept for an airplane is thrust reversal. In a sailing ship astern propulsion can be achieved by the appropriate manipulation of the sails. In square-rigged ships 'backing the sails', that is, aligning the sails so that the wind impinged on the bow surface, could provide sufficient retrograde thrust to slow or reverse the ship.
Reverse thrust can be generated to aid braking after landing by reversing the pitch of variable-pitch propeller blades, or using a thrust reverser on a jet engine. Rotary wing aircraft and thrust vectoring V/STOL aircraft use engine thrust to support the weight of the aircraft, and vector sum of this thrust fore and aft to control forward speed.
The propellers of a DC-6 are designed to provide reverse thrust after the aircraft touches down. The pilot then retards the throttle levers to a point below idle speed and that directs the electric mechanisms in the propeller hub to rotate the blades to a position in which they will provide reverse thrust. [6]
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. Rolls-Royce Tay 650-15 on a Fokker 100 of a type similar to the accident aircraft, with thrust reverser actuated.
After extending the landing gear, the propeller speed began to increase, startling the crew due to the audible noise. The aircraft's speed and altitude then rapidly dropped. The crew realised that the reverse thrust had been deployed in mid-flight and tried to save the aircraft.