Small, single-engine aircraft are the mainstay of recreational flying, and provide many hours of generally safe enjoyment for hundreds of thousands of enthusiasts worldwide. However, with only one engine on-board, they are also often only a small malfunction away from becoming a heavy, unpowered glider in dire need of somewhere to land. To help improve this situation, researchers at Universidad Carlos III de Madrid (UC3M) and AXTER Aerospace have created an auxiliary electric propulsion unit designed to be installed in conventionally-powered light aircraft to both increase available power and provide extra range in the event of an engine failure.

Primarily aimed at improving the safety of light passenger aircraft with masses of up to 750 kg (1,650 lb), the retrofittable electric propulsion system has been created in direct response to a perceived need in the light aircraft space.

"We are trying to saves lives and prevent accidents related to loss of power during flights, when the engine fails or the fuel runs out," says Miguel Ángel Suárez, from AXTER Aerospace. "We mustn’t forget that every year in Europe and USA there are an average of 600 accidents, 70 deaths and 24 million euros (US$27 million) in losses recorded."

The new arrangement sees an electric engine coupled to the conventional engine via the conventional drive system. There's also a high-efficiency lithium battery charged by the plane’s conventional engine, and an automatic electronic control system that automatically adjusts the electric drive motor to the needs of the plane.

"If there is a problem with the main engine, this electric engine will start to function, which will provide an additional range of about 20 kilometers, enough for the pilot to land safely," said Andrés Barrado, head of the UC3M Electric Power Systems group.

An extra 20 km (12 miles) may not seem a lot, but given that most light aircraft fly in a pattern not too far from their originating airfield, it could make the difference between returning to the safety of the airport or crashing in a field.

Serendipitously, the emergency propulsion system can also add around 40 extra horsepower (30 kW), as needed and when selected by the pilot. Not quite in the realm of a super-powered electric unit like the Siemens 260 kW (340 hp) monster, perhaps, but a handy addition to the lowly-powered engines of many light planes nonetheless.

"We maximize the capacity of the battery in generating movement with the electric engine, and we have found that we can also use the system as a hybrid for light aircraft: the pilot can activate it when she wants, adding up to 40 horsepower for take-offs or whatever is needed," said Daniel Cristobal, from AXTER Aerospace.

Currently being promoted and patented around the world, the creators claim that their system can be installed in all manner of light aircraft, either as a retrofit or in the construction of new aircraft. Claimed to reduce operating and maintenance bills, whilst lowering fuel consumption, the makers also assert that it may one day also be available for other types of craft, including gyroplanes, drones and UAVs.

The short video below shows testing and use of the new system.

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