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 :-)
This is called Powerback, most aircraft can do it, but it is not done very often.
In Jet aircraft, the two main problems are:
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.
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.