US producer of uncrewed aerial vehicles (UAVs) General Atomics Aeronautical Systems has completed durability testing on a new engine powered by heavy aviation fuel.

The new powerplant, dubbed the Heavy Fuel Engine (HFE) 2.0, is being developed as part of a modernisation effort for the General Atomics MQ-1C Gray Eagle. A flight testing programme was funded by the US Army under a $398 million contract awarded in 2023.

General Atomics on 29 May said it had completed ground durability testing on the HFE 2.0 earlier in the month. The trials simulated a full 2,500h engine life operating under what the company calls “the highest flight loads that could ever be seen in the field”.

Gray Eagle 25M GE-25M

Source: General Atomics Aeronautical Systems

General Atomics completed the first test flight of the GE-25M modernised Gray Eagle in January

Also included in the tests were conditions simulating 1,250 full-power take-offs and climbs to high-cruising altitude, and over 200 hours of cruise under worst-case generator loading conditions.

“Our HFE 2.0 engine is now the best heavy fuel engine in aviation,” says General Atomics Aeronautical Systems president David Alexander.

The UAV manufacturer partnered with UK automotive firm Cosworth to develop the prototype engine, spurred by what Alexander describes as “diminishing manufacturing sources for aviation heavy fuel engines and components”.

The HFE 2.0 had previously completed its first test flight in June 2023, aboard an existing Gray Eagle variant. A final 150h qualification test is scheduled to be completed in September, followed by certification of the HFE 2.0 from the US Army.

If that goes well, the new engine could see service in both the modernised Gray Eagle UAV, which General Atomics has designated the GE-25M, and the army’s existing fleet of MQ-1Cs.

Boasting 200hp compared to the current engine’s 180hp, the HFE 2.0 promises improved durability and reliability. General Atomics says the new powerplant will offer 50% more electrical power for onboard systems and sensors, while simultaneously increasing the time between required engine replacement by some 40%.

“The new engine, gearbox and generator design decreases major maintenance actions and virtually eliminates the need for overhaul,” General Atomics says.

The GE-25M test programme is also certificating an improved flight computer that will provide a fivefold increase in processing speeds and 80 times the amount of data storage, compared to existing Gray Eagles.

In addition to allowing the fielding of more powerful sensors, those improvements will also support the US Army’s push to incorporate autonomy into its aerial systems.