Thrust Reversal

Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's exhaust so that the exhaust produced is directed forward, rather than aft. This acts 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 distances. Such devices affect the aircraft significantly and are considered important for safe operation by airlines. There have been accidents involving thrust reversal systems.

Reverse thrust is also available on many propeller-driven aircraft through reversing the controllable pitch propellers to a negative angle. The equivalent concept for a ship is called astern propulsion.

                                               

In most cockpit setups, reverse thrust is set when the thrust levers are on idle and by pulling them further back.^[1] Reverse thrust is typically applied immediately after touchdown, often along with spoilers, to improve deceleration early in the landing roll when residual aerodynamic lift and high speed limit the effectiveness of the brakes located on the landing gear. Reverse thrust is always selected manually, either using levers attached to the thrust levers or moving the thrust levers into a reverse thrust 'gate'.

The early deceleration provided by reverse thrust can reduce landing roll by a quarter or more.^[4] Regulations dictate, however, that a plane must be able to land on a runway without the use of thrust reversal in order to be certified to land there as part ofscheduled airline service.

Once the aircraft's speed has slowed, reverse thrust is shut down to prevent the reversed airflow from throwing debris in front of the engine intakes where it can be ingested, causing foreign object damage. If circumstances require it, reverse thrust can be used all the way to a stop, or even to provide thrust to push the aircraft backward, though aircraft tugs or towbars are more commonly used for that purpose. When reverse thrust is used to push an aircraft back from the gate, the maneuver is called a powerback.