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Can commercial airliners theoretically taxi backwards using reverse thrust?

If this is possible, why isn't it common? I can already imagine some safety reasons but it would be nice to hear it from someone who knows :-)

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Very common on turboprops as the prop angle can be changed to produce reverse thrust a lot more efficiently than a jet thrust reverser! –  Brian Knoblauch Aug 11 at 19:14
    
I have seen it done with DC-9s many years ago. –  Cimbian Aug 12 at 18:04

2 Answers 2

up vote 29 down vote accepted

This is called Powerback, most aircraft can do it, but it is not done very often.

In Jet aircraft, the two main problems are:

  • The reverse thrust tends to throw a lot of debris in the air, because the exhaust is deflected to the sides and up and down too, which can damage both the engine itself and other things around the aircraft. It is less of a problem for aircraft with tail-mounted engines (so DC-9s often used powerback), but that layout is not used much any more as it is less aerodynamically efficient.
  • Reverse is rather inefficient on Jet engines, so it uses a lot of fuel.
  • As casey mentioned in comment, you have to be careful with brakes during powerback. The main wheels are rather close behind centre of gravity, so harder braking would lift the nose wheel (so you loose control) and you could even hit the tail on the ground and damage it.

So a tug is both cheaper and safer.

In propeller aircraft reverse is more efficient and it does not throw up debris that much, so it is sometimes used. But tug is still preferred, because transport aircraft don't have any rear visibility and so the pilots don't see where they are taxiing. With tug the tug driver does and the ground marshaller walks along with intercom connected to the plane.

Last, aircraft are able to turn almost on the spot, basically around one of their main wheels. The nose wheel can usually turn to about perpendicular and using differential brakes and differential thrust the aircraft can be turned with one main wheel almost not moving. So at airports with few facilities where asking for tug might be too much there is generally enough space around the aircraft so it does not need to reverse.

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I didn't think about the fuel consumption. Nice answer, thanks! –  André Stannek Aug 11 at 11:21
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@AndréStannek wheels are aft of CG, so braking will create a nose-up torque and sit the airplane on its tail. Standard procedure during powerbacks is "feet on the floor" to avoid inadvertent brake application. –  casey Aug 12 at 12:00

It can be done, in fact the DC-9 and MD-80 aircraft are approved for backing up using reverse thrust. It is called "powerback".

It is rarely used since it is quite fuel consuming, noisy and increases the risk of sucking up debris near the gate area causing damage to the engines.

Here's a video of an MD-80 backing up.

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Those reversers deploying look like something out of Transformers! –  David Richerby Aug 11 at 10:35
    
@DavidRicherby would you believe that it's only 2 links and an actuator to get that movement? –  ratchet freak Aug 11 at 10:42
    
Wow, seeing a plane back up be itself just seems wrong :-D Thanks! –  André Stannek Aug 11 at 11:18
    
Wow that powerback is NOISY! –  shortstheory Aug 12 at 10:07
    
@DavidRicherby those are known as target/bucket reverse thrusters: en.wikipedia.org/wiki/Thrust_reversal#Target_type –  shortstheory Aug 12 at 10:09

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