It is always difficult and sometimes dangerous to estimate future trends and events. Nevertheless, it is a most satisfactory outlet for one's imagination and it is, to some extent, necessary unless we are to abandon all attempts at shaping our own future.

Before trying to forecast the future of the helicopter, I feel that I must define what I mean by a helicopter. Resort to the English Dictionary does not help greatly; as is so often the case, it has been left behind by progress.

A helicopter is described as “a flying machine that should rise vertically by airscrews revolving horizontally.” Derivation from the Greek, helix—a spiral, and pteron—a wing. This definition indicates that every aeroplane having a thrust loading of less than one is a helicopter, unless it is propelled by rockets, ramjets or pulse jets!

The dictionary definition of an aeroplane is “ a flying machine heavier than air using planes.”