VerdeGo Unveils Hybrid-Optimized Version Of SR305 Diesel Aeroengine

U.S. startup VerdeGo Aero and Germany’s Roder Prazision have developed a version of the SR305 diesel-cycle aeroengine for use in hybrid-electric powertrains.

VerdeGo’s 185-kW (250-hp) VH-3-185 hybrid powerplant will be displayed at the AirVenture 2023 show in Oshkosh, Wisconsin, on July 24-30.

VerdeGo and Roder subsidiary SMA Aero Engines collaborated to develop a version of the four-cylinder, 230-hp SR305 piston engine, the SR305-VDG, optimized for use in a hybrid-electric powertrain. Changes increased power output and reduced the weight and volume of the hybrid powerplant.

“Creating an optimal hybrid powerplant requires careful alignment of all the major components to ensure they function efficiently and reliably together,” VerdeGo CEO Eris Bartsch says. The hybrid powerplant includes a tightly integrated engine, motor/generator, power electronics, control system and thermal management.

“We are confident that this new version of the engine will form the powertrain for several new electric aircraft that require an energy density currently unattainable with battery technology,” says Jorg Erdmann, Roder chief operating officer. Equivalent energy density including fuel is 600-1,000+ Wh/kg compared with less than 300 Wh/kg for batteries.

After more than two years of development and testing of the SR305-VDG, VerdeGo will display its VH-3-185 at AirVenture in the booth of the U.S. Air Force’s AFWerx innovation unit, which has provided funding to support development of the hybrid powerplant.

The VH-3-185 can be used in parallel or series hybrid powertrains, providing a combination of shaft and electrical power. Already certified, the SR305 burns jet fuel, providing the potential to run the hybrid powerplant on sustainable aviation fuel to reduce life-cycle CO2 emissions.

SMA was formed in 1997 by Socata and Renault to develop a diesel-cycle engine for general aviation aircraft. Snecma (later renamed Safran) joined the program, and in 2005 became the sole owner of SMA. 

In 2021, Rorder acquired SMA from Safran, along with the type certificate for the SR305 and supplemental type certificate for its retrofit installation in the Cessna 182. Roder is now working to certify the six-cylinder, 300-hp-plus SR406 engine.