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...
This is called Powerback, most aircraft can do it, but it is not done very often.
In a jet aircraft, the three main problems are:
So a tug is both cheaper and safer.
In propeller aircraft, reverse is more efficient and does not throw up as much debris, so it is sometimes used. But a tug is still preferred because transport aircraft don't have any rear visibility, so the pilots can't see where they are taxiing. With tug the driver can see behind the aircraft, and a ground marshaller walks along side each wingtip with an intercom connected to the plane.
Lastly, since aircraft are able to turn almost on the spot using differential braking and thrust and 180-degree nosewheel steering, at airports with few facilities there is generally enough space around the aircraft to permit the pilot to reverse out easily.
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.
Can commercial airliners theoretically taxi backwards using reverse thrust? - After an airshow at RNAS Yeovilton, Somerset in the 1980s a British Airways Concorde found it could not taxi out for departure as it had been parked too close to an adjacent hangar (and didn't have the required turning circle)... there was no suitable towing gear on site, or within easy reach... so after a discussion with his engineers the pilot decided to reverse taxi a short distance using reverse thrust.... the centre of gravity was adjusted by transfering fuel to the forward fuel tanks, fingers were crossed, and... it worked! (I was there to see it, working in the control tower)