Different Methods of Obtaining Reverse Thrust on Aircraft

As a plane descends and prepares for landing, it conjures an incredible amount of force around it. Planes are typically traveling at about 200 miles per hour when touching down on the runway; thus, they require a superb braking system. Even when idle, thrust is produced and travels forward as it acts against the deceleration systems. The braking system on aircraft are sufficient enough to stop most aircraft, yet in case of emergency, another deceleration method is needed for safety purposes and to prolong the longevity of the brakes.

An efficient modus operandi to achieve this need is thrust reversal. Thrust reversal is the process in which the engine of the aircraft temporarily redirects the thrust forward instead of backward. The reversal of the thrust counteracts the forward travel of the aircraft and assists in deceleration. Thrust reversal has also been used to reduce the airspeed mid-flight. Reverse thrust can be generated by a reversible pitch propeller, or on a jet engine by a target reverser.

Reverse thrust is usually enacted immediately after the plane touches down when aerodynamic lift limits the effectiveness of the brakes. It is always operated manually by the pilot, utilizing thrust levers to maintain full control. Although thrust reversal is a supplemental tool in bringing the aircraft to a stop, regulations dictate that an aircraft must be able to land regardless of the use of thrust reversal.

There are several different methods of obtaining reverse thrust on aircraft. The first one involves clamshell type deflector doors to implement a reversal of the gas exhaust stream. Another method involves utilizing external doors to reverse the exhaust flow. The last process involves fan engines using blocker doors that reverse the airflow.

Once the speed of the aircraft has slowed, it is crucial to shut down the reverse thrust to prevent the reversed air from lifting debris in front of engine intakes. If debris is ingested, it can cause severe damage. A powerback is when reverse thrust is used to move an aircraft away from the gate. Reverse thrust performs optimally when the aircraft is at higher speeds.

Smaller aircraft don’t require thrust reversal systems except in specialized situations.