Helix, the UK manufacturer of the world's most power-dense electric motors and inverters, has partnered with RED Aircraft to develop a series hybrid generator solution for aviation: the RED A03 Series Hybrid Generator.

The RED A03 Series Hybrid Generator brings together the RED A03 V12 diesel engine, one of the lightest and most efficient piston engines in aviation history, with a specially configured variant of Helix's SPX177 motor: the SPX177-137D.

The SPX177-137D is a 2×3-phase synchronous permanent magnet radial flux motor, designed specifically for use-cases where weight and space are at a premium. Massing just 21.7kg, the SPX177-137D outputs 420kW of peak power and 327kW of continuous power. This means it achieves a peak power density of 19.4kW/kg, and a continuous power density of 15.1kW/kg. This is all achieved in a volume of only 7.5 litres: 192mm in diameter and 258mm in length.

By pairing the SPX177-137D with a 1:5.4 planetary transmission and a RED A03 engine, the RED A03 Series Hybrid Generator can offer aviation a pre-integrated electrical generation capability without precedent. With a dry mass of just 350kg, the generator can output 380kW peak electrical power for 5 minutes and 327kW continuous power – something that typically requires a 2-tonne unit for marine and industrial applications.

As a dedicated series hybrid generator, the new unit's electrical power density is three times greater than existing auxiliary power units. It also achieves major efficiencies in fuel economy – with a fuel burn rate of 77kg/h, at an energy efficiency of 218g/kWh BSFC in the optimum. Compared to equivalent turbine engines, this means 50% fuel savings and 50% less CO2 emissions.

The maximum noise of the RED A03's V12 is only 75 decibels at 50 metres, significantly lower than comparable aviation generation solutions. This makes it an ideal generator for eVTOLs and Air Taxis landing and taking off in city centres, and for commercial aircraft that must comply with on-the-ground noise limits at airports.

Jim Edwards, Chief Engineer at Helix, said: "Helix's motors are a perfect technology for aerospace series hybrids, since their power density makes them an order of magnitude lighter than any other solution on the market. By partnering with RED Aircraft – a team in the combustion world who achieve world-leading power density with their engines – we've been able to contribute to a series hybrid generator without precedent in aerospace history."

Christian Mundigler, Director Sales & Commercial Development at RED Aircraft, said: "Until now, series hybrid power generation for aircraft involved a compromise: repurposing jet-engine auxiliary power units, or adapting heavy land-based systems. The RED A03 Series Hybrid Generator removes this compromise, offering a dedicated electrical generation solution that leverages RED Aircraft's world-class expertise in developing lightweight and efficient aviation piston engines. By pairing our engine technology with Helix's power dense motors, we've unlocked an entirely new range of opportunities for low-emission flight. We're excited to follow up our first series hybrid generator with additional variants using RED Aircraft's V8, I6, and I4 engines – capable of outputting 280kW, 210kW and 140kW of electric power."