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Thrust reverser is the
reversal of aircraft thrust to slow down the aircraft. Use of thrust reverser
in flight is rare. Airplane thrust reverser is usually used during landing to
reduce the landing roll and minimize brake wear.
The aircraft thrust is
directed towards the aft direction. Although ideally if the thrust is reversed
completely in opposite direction to forward thrust the braking would have been
more effective. But thrust reverser structure allows reversal of thrust at a certain
angle, so the affectivity of the braking potential is not completely realised. However,
thrust reverser do provide braking at critical times like rejected takeoff,
landing on wet runway and landing on short runway, although it is also used in
normal landing.
Types
of thrust reverser:
Piston
engine thrust reverser
Piston engine thrust
reverser uses reversible pitch propeller blade to change the blade angle to
achieve thrust reversal. The propeller blades are airfoil shaped. So as per Bernoulli’s
theorem the forward thrust is achieved because of higher pressure aft of the
blade as compared to the forward section. By changing the blade angle the
thrust is reversed.
Jet
engine thrust reverser
Jet engine thrust reverser
redirects the exhaust or bypass air in the forward direction thus achieving
thrust reversal. Jet engine thrust
reverser is classified by the mechanism as to how the thrust is reversed:
Clamshell
thrust reverser or Cascade thrust reverser- The clamshell
thrust reverser or cascade thrust reverser is pneumatically operated. When activated
the thrust reverser doors operate to divert the thrust in forward direction. The
clamshell thrust reverser, usually divert the bypass air and not the core
exhaust. This type of thrust reverser is usually seen in turbofan engine.
Bucket
thrust reverser or Target thrust reverser- The bucket reverser
or target thrust reverser is hydraulically operated. When activated the doors
block the primary exhaust and divert the thrust forward.
Cold
stream thrust reverser- The cold stream thrust reverser is
pneumatically operated. When activated the doors block the high bypass air,
direct the thrust forward and thus achieve thrust reversal.
Thrust reverser is an essential system for the operation of modern commercial aircraft. It’s an added safety to the aircraft.
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