what’s the use of the cart that pushes back the airplane? Can planes not reverse without it?

Question

what’s the use of the cart that pushes back the airplane? Can planes not reverse without it?

In: 188

Answer 1

Aeronautical engineer here:

The real reason why airplanes don’t go backwards using reverse thrust is not noise, it is the risk of an engine surge.

Reverse thrust is only used during landing while the airplane is still going forward at a certain speed (notice that the reverse thrust is shut way before the airplane is at rest, during landing). The risk is that the engine sucks back up its exhaust gases + the fact that reverse thrust increase considerably the air flow pressure in the rear side of the engine. At low speed, if this pressure gets too high, the air struggle to moves backwards in the engine and the air flow can stall in the compressor leading to a [compressor surge](https://en.m.wikipedia.org/wiki/Compressor_stall) which is very damaging.