The on-line dictionary definition describes a helicopter thus:
Quote:
helicopter
ˈhɛlɪkɒptə/
noun
noun: helicopter; plural noun: helicopters
1.
a type of aircraft which derives both lift and propulsion from one or more sets of horizontally revolving overhead rotors. It is capable of moving vertically and horizontally, the direction of motion being controlled by the pitch of the rotor blades.
That might be the Common Man's definition, but the European Rules of the Air...
‘helicopter’ means a heavier-than-air aircraft supported in flight chiefly by the reactions of the air on one or more powerdriven rotors on substantially vertical axes;
2 s