Petrol-electric hybrid aircraft is first to charge in flight

The aircraft, developed by researchers from Cambridge University with funding support from Boeing, is powered by a parallel hybrid-electric propulsion system where an electric motor and petrol engine work together to drive the propeller.

It uses up to 30 per cent less fuel than a comparable plane with a petrol-only engine, and is also able to recharge its batteries in flight, the first time this has been achieved.

Until recently, although such hybrid systems were suitable for cars, the technology could not be transferred into the aviation sector as the batteries required were too heavy and had insufficient capacity. However, the development of improved lithium-polymer batteries has made hybrid planes a possibility.

The current demonstrator is a commercially available single-seat aircraft, which uses a combination of a four-stroke piston engine and an electric motor and generator coupled through the same drive pulley to spin the propeller.

During take off and climb, when maximum power is required, the engine and motor work together to power the plane. Once cruising height is reached, the electric motor can be switched into generator mode to recharge the batteries or used in motor assist mode to minimise fuel consumption.