Why do engines 'accelerate' after landing? What thrust reversers are and how they work
In English it is referred to as 'thrust reverse'. In Italian thrust reversal. It is that which is applied [...]
Delta
In English it is referred to as. 'thrust reverse'. In Italian thrust reversal. It is the one that comes Applied to jet thrusters (but also exists on turboprops) immediately after landing, To reduce the stopping distance of the aircraft, at the same time 'lightening' the work of the brakes.
In this article:
Passenger aircraft touch the ground at a speed that depends on their mass, but indicatively Is between 250 and 300kmh. And braking action is inversely related to track length. Plane decelerates thanks to aerobrakes, which on today's technologically advanced planes 'lift' off the wings automatically as soon as the rear gears touch the runway, to the brakes and, indeed, to the thrust reversers.
The latter, over the years, have taken the most diverse forms. When they were still around aircraft with engines positioned at the rear of the fuselage, were shaped like two shells of a seashell that closed at the rear of the engine, diverting the flow of the powerplant forward. Today this system is still adopted by Boeing 717s in use with Delta and at Hawaiian Airlines, for example. But it was aboard popular jets in the 1970s, 1980s and 1990s, such as the Douglas Dc-9, the Fokker 70 and -100, and the McDonnell Douglas MD-80.
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On planes that have engines hanging under the wings, thrust reversers, on the other hand, are of two types: those, so to speak, in the shape of a petal corolla (as in the case of some Airbus A320, A330 and A340 engines).
And those that simply consist of a cylindrical section of the engine nacelle being translated backward and which has inside it many 'cells' that deflect the thrust of the thrusters forward.
For thrust reversers to be effective, it is not enough for the pilot to activate them, but must also increase the power of the engines for the flow of gases emitted in the opposite direction from that of the plane's motion to be effective. Therefore, a few moments after landing, the engines are accelerated (even though their maximum back thrust is about half that of forward thrust).
In recent years, brakes have become increasingly high-performance, allowing less 'intensive' use of thrust reversers. Therefore, on Airbus A320s, the latest generation Boeing 737s, and even all new long-haul models, thrust reversal (also for fuel consumption reasons) is used sparingly, unless runway length advises otherwise.
Quite different were the landings of older aircraft such as the DC-9s and MD-80s, which fans remember with emotion and nostalgia, which would explode in a veritable roar of retrospect as soon as the carts were placed on the ground. Other (good) times...
