Most of the components of an airplane are similar to the helicopter’s. A helicopter generates lift and propulsive thrust through a rotor system. This system is driven by the engine of the helicopter.
Most of the helicopters consist of a main rotor and an auxiliary rotor. The latter is to overcome the torque of the main rotor and maintain the directional control. Unlike the fixed wings, in helicopters the flight and landing force acts on the main rotor.
Due to the continuously rotating components, helicopter encounters high level of vibrations that leads to metal fatigue. This problem has led manufacturers to use composite construction technology.
Earlier, the manufacturers used steel tube construction. No doubt, this was a strong structure, but had poor strength to weight ratio and bad aerodynamic properties. The construction was evolved to sheet metal with the introduction of semimonoque and monoque designs. This possessed high strength to weight ratio as well as better aerodynamic properties.
Nowadays, manufacturers use advanced composite materials for commercial helicopters.
In Sikorsky S-76, the following materials were used –
- Kevlar sheet
- Kevlar honeycomb
- Aluminium sheet
- Aluminium honeycomb