Thrust reversal, also called reverse thrust, is an operating mode for jet engines equipped with a thrust reverser in which thrust is directed forwards to decelerate the aircraft after landing. The reverser unit, classed as an element of the engine exhaust system, works by interrupting the exhaust stream as it leaves the engine and turning it partially forwards. By changing the direction of the exhaust, the device redirects engine thrust forward, helping slow the aircraft.
Reverse thrust can be generated either by a reversible-pitch propeller or, on a jet engine, by a target reverser or a cascade reverser installation.
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Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the definition of reverse thrust on a plane?
Thrust reversal is an operating mode for jet engines equipped with a thrust reverser, and reverse thrust is used to decelerate an aircraft after landing or in the event of a rejected take off. Reverse thrust uses the engines to slow the aircraft down, and engaging reverse thrust redirects where the airflow goes as it leaves the engines.
Reverse thrust is thrust projected in the opposite direction to normal. It is also known as thrust reversal.It keeps the engines rotating in their normal direction but redirects where the airflow goes as it leaves the engines, so it creates a decelerating force on the aircraft's direction of travel.
Reverse thrust is created when the propeller pitch angle is reduced from fine to negative-the beta position-so that controllable-pitch propellers direct thrust forward instead of aft, and on turbofan engines it deflects engine exhaust through more than 90 degrees and up to 135 degrees. Cascade or target reverser installations accomplish this deflection for jets, while reversible-pitch propellers accomplish it for turboprops.
Reverse thrust is sometimes selected on idling engines to eliminate residual thrust, preventing jet-blast damage and increasing braking effectiveness on icy or slick conditions.
What is the purpose of thrust reversers in an airplane?
Thrust reversers give additional stopping force on wet, slushy and icy runways, providing a safety margin when wheel brakes alone do not suffice. They supplement autobrake systems and reduce reliance on aerodynamic braking, shortening landing roll distance and preserving brake integrity.
Airlines also use them for directional control during rejected takeoff and to improve runway length management. By reducing brake wear, the devices lower maintenance intervals and enhance operational safety in tough conditions.
The main aim of thrust reversers is to improve the aircraft's deceleration capacity after landing. By sharing the deceleration load, thrust reversers reduce brake fade and extend the service life of wheel brakes, which endure high temperatures during touchdown.This role is essential for functional security and economic operation.
Do airplanes use reverse thrust?
Yes-once the aircraft has touched down. Aircraft engines can be set to reverse thrust mode during landing, and most large passenger aircraft will deploy reverse thrust on landing. Most modern passenger aircraft such as the Airbus A350 and Boeing 787 use cold stream reversers.The Airbus A380 features a thrust reverse system that is unique amongst four-engine aircraft.
Reverse thrust is intended only to slow the airplane, not to move it backward on the ground. Airplanes do not have a reverse gear. Pushback tractors are used because airplanes are meant to go forwards. An airplane almost never uses reverse thrust to move in reverse. Airplanes need to go in reverse only when they push back from their gate, and for that maneuver tugs do the work.
How do airplane thrust reversers work?
A thrust reverser works by changing the direction of the exhaust as it leaves a jet engine. On propeller-driven aircraft, reversible pitch propellers change blade angle so that thrust direction is reversed without extra hardware. On pure-jet or high-bypass engines, the fan produces most of the thrust, so designers block or divert this flow. Cascade reversers use cascade vanes hidden around the circumference of the engine nacelle.
When reverse is needed, the sleeve slides aft, uncovering the cascade vanes, and blocker doors deploy inside the bypass duct to stop rearward fan air. The blocked air is forced out through the cascade vanes, which are angled to direct the airflow forward.
Bucket reversers, also called target reversers, use hydraulically operated bucket doors to reverse the hot gas stream. Clamshell reversers are a bucket type. A clamshell reverser hides its doors inside the tailpipe and uses hinged doors to redirect exhaust gases forward. Clamshell reversers are noisy. After touchdown, the autobrake engages as soon as the main landing gear touches down, and wheel brakes take increasing share of deceleration as speed decreases, while the hot exhaust still provides a bit of forward thrust until the reverser system modulates to idle.
