Several years ago it became apparent that there was a need for some means of reversing the thrust of jet engines on landing—the equivalent of reversing pitch propellers on piston and turbo-prop engines.

Many different designs were investigated on the drawing-board, with experimental backing in some cases, and when the best configurations had crystallised detail work started on a reverser for the Avon engine. While this was being developed a second design, identical in its main principle but different in many small ways, was prepared for the Conway engine.