Hybrid propulsion for helicopters

EADS has presented a diesel-electric hybrid propulsion system for helicopters at the ILA Berlin Airshow that promises to make the aircraft more fuel efficient and environmentally friendly.

Developed by EADS Innovation Works, the corporate research and technology network of EADS, the Eco2Avia research platform is expected to open up new possibilities for cleaner, safer and more quiet helicopter and aviation operations.

According to EADS, highly efficient electrical motors driving the rotors, combined with diesel engines, reduce fuel consumption and emissions by up to 50 per cent and take-offs and landings are possible on electrical power alone, resulting in lower noise levels and improved flight safety.

The main components of this patented hybrid system are multiple diesel-electric motor-generator units, a pair of high-performance batteries and a power electronics unit controlling the energy flows for best efficiency.

Diesel-electric hybrid propulsion system for helicopters
Diesel-electric hybrid propulsion system for helicopters

The OPOC (Opposed Piston, Opposed Cylinder) diesel engines are claimed to offer a fuel economy improvement of up to 30 per cent compared with today’s helicopter turbine engines.

The OPOC engine’s power output shafts are fitted with advanced, weight-optimised generators delivering electrical current to the power electronics unit. This unit manages the distribution of the electricity to the electrical motors driving the main rotor and the tail rotor, to and from the batteries as well as to the other user systems on the helicopter.

The four independent energy sources of this kind of propulsion system ensure very high levels of flight safety and efficiency. EADS further claims that several different kinds of combustion engines could be integrated into such a hybrid system.

The hybrid system architecture allows the main rotor and its electrical drive to be tilted forward during cruise flight, enabling the helicopter’s fuselage to remain at its optimum alignment with the airstream, minimising aerodynamic drag and reducing the power demand and the fuel consumption.

Since the tail rotor has no mechanical linkage to the main rotor and its power source, it can be turned off at higher speeds. During these flight phases, stability and control as well as balancing of the rotor torque are provided by the aerodynamic properties of the helicopter’s tail fin and rudder.