Three principal thrust-reverser families-clamshell, cascade, and fan-door-translate jet forward momentum into rapid deceleration the instant the pilot lifts the handles on landing. The types of aircraft thrust reversers are outlined below.
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Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
1. Clamshell Type Thrust Reverser
A clamshell-type thrust reverser is a hinged door or clamshell-like structure that covers the rear section of the engine exhaust nozzle. When deployed, a pair of hydraulically or pneumatically operated bucket-shaped doors swings into the hot gas stream, reverses its direction, and thus creates reverse thrust. Because these doors form the propelling nozzle of the engine for forward thrust, the same hardware performs two functions: in normal flight the doors seal the jet pipe, and on landing they pivot outward to deflect the jet forward. They are usually pneumatically or hydraulically actuated and must be built to withstand high temperatures because they handle the hot exhaust gases directly.
Target-type thrust reversers are also called clamshell thrust reversers. Older generation low-bypass turbofan and turbojet engines relied on this layout. The design was specifically developed for turbojet engines that have only hot exhaust airflow.. Classic examples are found on the BAC One-Eleven, some older business jets, the VC-10, the Russia-made Tupolev Tu-154, and the Ilyushin Il-62. Rolls-Royce applied clamshell-type thrust reversers to the Conway, Tay, BR715, and AE3007A engines, while the Pratt & Whitney JT8D used the same arrangement. The mechanism is noisy and adds weight. Everything happens inside the nozzle, so the system is difficult to spot from the outside.
2. Bucket Type Thrust Reverser
A bucket-type thrust reverser is a hydraulically actuated system that uses two large bucket-like doors attached to the rear of the engine over the exhaust system. In forward thrust mode, these doors form the smooth cone shape of the engine's exhaust nozzle, creating a convergent-divergent final nozzle that preserves propulsive efficiency. When the pilot selects reverse, hydraulic actuators swing the buckets out and back, pivoting them to form a barrier behind the engine. The actuator incorporates a mechanical lock in the extended position to hold the doors securely deployed.
With the buckets deployed, the rearward flow of the exhaust is blocked and the hot gas stream is deflected forward through a redirected exhaust with a forward component, producing powerful reverse thrust for deceleration. Because the bucket doors reverse both core and bypass flows, bucket-type reversers are more efficient than cascade thrust reversers, achieving reverse thrust ratios up to 49 percent. The design offers the lowest weight penalty among reverser types. It gives pilots a way to steer against asymmetric force, shortening landing distance and reducing tire brake wear.
3. Cold Stream Type Thrust Reverser
The third type is the cold stream system, a reverse thrust configuration commonly used in high bypass turbofan engines. Cold stream thrust reversers are essentially any reverser that only directs the cold stream of air bypassed in modern turbofan engines; they redirect the fan's thrust by deflecting this cold, bypassed air forward. In normal flight, the bypass air generates the majority of engine thrust, so the cold stream design takes advantage of this large airflow without touching the hot core exhaust. The system works by redirecting bypass airflow utilizing doors installed in the bypass duct: when reverse is selected, the doors swing into the bypass region and block the cold stream final nozzle, forcing the air forward out of cascade vanes or sideward openings.
Because the exhaust from the combustion chamber continues to generate forward thrust, the cold stream reverser is less effective than systems that also reverse the hot stream, yet it is lighter and simpler. Modern passenger aircraft such as the Airbus A350 and Boeing 787 use cold stream reversers; the Airbus A380 features a unique arrangement with cascade type reversers fitted only to the inboard engines. The cold stream reverse system is actuated by an air motor whose output is converted into mechanical movement by flexible drives, gearboxes, and screwjacks, and an actuator incorporates a mechanical lock in the extended position to hold the doors firmly in place.
