What is the RED Aircraft and Helix series hybrid generator for aviation?

It is a hybrid power system for aircraft that pairs RED Aircraft's A03 V12 diesel engine with Helix's SPX177-137D electric motor. Together they form a generator producing electrical power for aircraft systems, rather than driving a propeller directly.

How much power does the generator produce?

The complete generator outputs 380kW of peak electrical power for five minutes and 327kW continuously, according to Helix.

How much does the generator weigh?

The complete generator has a dry weight of 350kg. The electric motor component alone, the SPX177-137D, weighs 21.7kg.

Who makes the engine and motor used in the generator?

The diesel engine is RED Aircraft's A03 V12, built by Raikhlin Aircraft Engine Developments GmbH in Adenau, Germany. The electric motor is Helix's SPX177-137D, developed by the UK's Integral Powertrain Limited.

Why does the generator matter for aviation?

Aircraft electrical generation has typically relied on gas-turbine auxiliary power units. Helix says this piston-electric generator offers comparable or greater output at a fraction of the weight, though this claim comes from the manufacturer and has not been independently benchmarked.

Is the generator quieter than existing systems?

Helix states maximum noise is 75 decibels at 50 metres, which the company positions as lower than comparable turbine-based systems, relevant to noise-sensitive operations near cities and airports.

Will the generator work for electric air taxis (eVTOL) and other aircraft?

RED Aircraft and Helix position the generator as suited to eVTOLs, air taxis, and commercial aircraft with on-the-ground noise limits, based on its stated weight, output, and noise figures.

What certification does the RED A03 engine hold, and does that apply to the generator?

The RED A03 engine has held EASA type certification since December 2014 under Type Certificate E.150, certified against CS-E requirements. This certification covers the engine itself. The sources reviewed do not confirm separate certification of the complete generator package.

How does the SPX177-137D's power density compare with existing auxiliary power units?

Helix states the SPX177-137D achieves a peak power density of 19.4kW/kg and continuous density of 15.1kW/kg, and describes the resulting generator's electrical power density as roughly three times that of existing auxiliary power units. These are manufacturer figures rather than independently verified benchmarks.

What is the roadmap for additional generator variants, and what does this mean for procurement?

RED Aircraft has said it plans further generator variants built around its V8, I6, and I4 engines, targeting 280kW, 210kW, and 140kW of electric power respectively. This points to a scalable product family rather than a single demonstrator, relevant to procurement teams evaluating hybrid-electric APU suppliers.

Series hybrid generator for aviation lands at 380kW and 350kg

Category: Aerospace, Motors, Power Electronics

July 15, 2026

Close-up of an aircraft propeller and spinner, used to illustrate Helix's new series hybrid generator for aviation.

The propeller may be the visible part, but the real story sits behind it, in a 350kg generator built to replace it

(Image courtesy of Helix)

RED Aircraft and Helix have introduced a series hybrid generator for aviation that pairs a V12 diesel engine with a radial flux electric motor. The unit produces 380kW of electrical power at a dry weight of just 350kg. For readers tracking power density gains across sectors, the figure that matters is not the output number itself. It is what the pairing displaces. Gas-turbine auxiliary power units have defined aircraft electrical generation for decades, and this offers a different starting point entirely.

Inside the RED A03 series hybrid generator

The generator combines the RED A03 V12 diesel engine with the SPX177-137D, a newly disclosed variant of Helix’s SPX177 motor line. The RED A03 has held EASA type certification since December 2014 under Type Certificate E.150, certified against CS-E requirements, and runs on Jet-A fuel through a V12 architecture. It is a 2×3-phase synchronous permanent magnet radial flux motor weighing just 21.7kg.

That motor delivers 420kW of peak power and 327kW continuous, inside a 7.5 litre package measuring 192mm across and 258mm long. Paired through a 1:5.4 planetary transmission, the complete genset outputs 380kW peak electrical power for five minutes and 327kW continuous. Helix states this achieves a peak power density of 19.4kW/kg and a continuous density of 15.1kW/kg for the motor alone.

Why power density matters for aviation generators

Helix reports the resulting electrical power density is three times greater than existing auxiliary power units, with the 350kg dry mass doing work that typically needs a two-tonne unit in marine and industrial applications.

Fuel economy is where the RED A03 pedigree does the work. RED Aircraft’s own published data shows the A03 family delivers up to 50% lower fuel consumption than comparable engines, a figure this generator carries forward at a stated 77kg/h burn rate and 218g/kWh BSFC in the optimum range. Helix frames this as a 50% fuel saving and 50% CO2 reduction against equivalent turbine engines. Noise is also lower, at a claimed 75 decibels maximum at 50 metres, a figure relevant to eVTOL and air taxi operators facing city centre and airport noise limits.

Positioning against turbine based auxiliary power units

The comparison point most useful to a specialist reader is not marine gensets but other hybrid-electric aviation power sources. Honeywell’s turbine-based turbogenerator, built around its HGT1700 APU, targets the 1MW class, a different segment to the RED A03 Series Hybrid Generator’s sub-400kW output. Where gas-turbine designs have historically dominated onboard power generation, the RED A03 Series Hybrid Generator brings a dedicated piston-diesel alternative purpose-built for this power class, with the fuel economy and noise profile that segment demands.

RED Aircraft has already signalled where this goes next. Christian Mundigler said the company plans to follow the V12 unit with generator variants built around RED Aircraft’s V8, I6, and I4 engines, targeting 280kW, 210kW, and 140kW of electric power respectively. That roadmap suggests a scalable family rather than a single demonstrator, which is the detail procurement teams evaluating hybrid-electric APU suppliers will want to track as certification work proceeds.

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