During development of solid metal airscrews in the U.S.A. many vibration failures occurred and various investigations have been made there and elsewhere with a view to overcoming such troubles. The problem is to avoid airscrew failures while keeping weight as low as possible; its solution involves mathematical analysis, further development of experimental methods, and investigations in relation to particular combinations of engine and airscrew.

I ought first of all to define what a gyroplane is.

A gyroplane belongs to the helicopter family, aircraft which, as their name indicates, have wings in the form of airscrews.

In effect a helicopter consists of large airscrews, with axes nearly vertical and set in rotation by the action of a motor; the reaction of the air on the blades provides the necessary lift to enable the machine to rise vertically, without forward speed.

I will recall that in order to obtain sustentation without forward speed many suggestions have been made for giving to wings a movement which would produce lift.