Wright Electric is developing the powertrain for a hybrid version of the C-130 transport aircraft, the Hercules, writes Nick Flaherty.

It would use two conventional turbines and two electric propulsors, with the batteries held in the cargo area, making it the largest aircraft to be electrified.

The project would use the second-generation, MW-class motor, the WM2500, built with support from the US ARPA-E programme and NASA space agency, which is nearly complete.

The stator is wound, the rotor is complete and all of the mechanical components are finished. Final assembly will begin later this year.

The WM2500 is a 2.5 MW electric propulsion unit, designed for ducted fan and propeller-based applications. It fits into the existing engine nacelle, says Colin Tschida, CTO of Wright Electric.

The 2×2 approach allows all four engines to be used for takeoff, and the two electric motors can be used for quieter, more stealthy flight at altitude.

The hybrid design would be able to carry six pallets, each with a volume of 463 L, although the payload will be reduced from 40,000 lb to 25,000 lb. Hybridisation can also save between 27% and 44%  of the fuel used.

The project needs improvements in the power distribution systems. NASA is working on lightweight, high-conductivity cables and advanced circuit breakers able to handle high voltages of 800 V and 1200 V safely at high altitudes.

Wright Electric is also developing a lightweight battery pack with an energy density of 1000 Wh/kg at pack level. 

“We have experience of building lightweight, thermally managed, electric propulsion systems, and we see a way to apply that knowledge to the design of large, molten battery packs,” said Tschida.

Initial packs will be released for lab testing in 2025, with the first rollout to early adopters targeted for 2027.