Even before the Wright Brothers flew the world's first airplane, Igor Sikorsky had already built a coaxial helicopter in Russia.

Since then, many famous names have been known in helping to shape up the final design and development of coaxial helicopters, such as Cornu, Asboth, Pescara, De Bothezat, Berliner, Bendix, Hiller and others.

Coaxial designs are attractive due to their basic simplicity. The power train is short and the airframe can take many shapes and can be custom built.

Figure 3 A Counter-Rotation Device

Counter-rotation eliminates feeding torque into the airframe. In hovering flight the lift force is only vertical, there is no tail rotor producing a side force requiring constant pilot intervention and hence the complexity of piloting a coaxial helicopter is completed eliminated.

Figure 4 An Early Coaxial Machine

In the early helicopter period many extraordinary models were developed by a number of great thinkers, however all those pioneers were missing two essentials: (1) a true understanding of the nature of lift and (2) an adequate lightweight engine with adequate power.

Figure 5 An Early Multi-blade Coaxial Machine