Why do jet engines reverse thrust?
Answers:
jet engines reverse thrust to arrest forward motion, to slow down.
they are called BRAKES. how do you think they slow down
How else do you think they parallel park?
the reverse thruster is intended to assist the brakes in short field operations.
stops faster then normal braking
Reverse trust is activate during initial stage to slow down the aircraft only after landing and never at flight,propellor driven aircraft alter the pitch to produce reverse trust after landing,some high aircraft deployed paracute to assist as a more effective initial braking more or less acting as a reverse trust,only when the plane has been slow down substancially the wheel brake are then activate for final stopping
Reverse thrust does not mean they stop and turn the other way. There are devises that divert the air forced out of the back of to the front ward in effect slowing the plane down during landing. Your question is Why? Well, brakes are not enough when you've got 50 tons of plane moving forward at 90 Mph. The Engines are utilized because of there strength and effectiveness. It is the same as down shifting on a car with manual transmission. The engine slows the forward motion.
Jets usually reverse thrust to slow down after they touch down on the runway. They also use the spoilers. This helps them slow down from 200 kts.
RC, you are close, but the fact is that the brakes ARE enough to slow a fully loaded plane down all by themselves, T/R's (thrust reversers) are not needed at all, except in a very few commercial airports, usually islands, St. Kitts, The Virgin Islands, etc, etc).
The reason they are used is the same reason why anybody does anything in this world, money.
Brakes are expensive, they are expensive to purchase, tho on commercial aircraft we remove them and send them off to be rebuilt.
Between the cost of rebuilding a brake unit and the time that the aircraft is down(tho most brake changes are done overnight while the plane is parked) and the manpower to pull the tire and then R&R the brake stack is costly, brakes last 40%~60% longer when used in conjunction with T/R's.
We often dispatch aircraft with the T/R's locked out due to one of them inop, and if it is wing mounted engine the one on the opposite side also has to be locked out.
Reverse thrust is the temporary diversion of a jet engine's output so that the exhaust gases are blown forwards rather than backwards. The resulting thrust force acts against the forward travel of the aircraft. Reverse thrust is used by many jet aircraft to help slow down just after touch-down, thus reducing wear on the brakes and enabling the aircraft to use shorter runways. It is also available on many propeller-driven aircraft through changing the pitch of the propeller blades to a negative angle, thereby directing air flow into the direction of travel
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