French eVTOL aircraft developer Ascendance plans to demonstrate its Sterna hybrid-electric propulsion system on a fixed-wing drone as part of a government-backed initiative to modernize observation capabilities at missile testing facilities.

The Direction Générale de l'Armement (DGA), France's defense procurement agency, is funding the project. It intends to use the hybrid-electric demonstrator vehicle for maritime surveillance and monitoring of tests launched by DGA Essais de Missiles (the DGA Missile Testing Center).

Announcing the development on February 10, Ascendance said it is collaborating with French drone manufacturer Delair to integrate the Sterna propulsion system with its partner’s DT46 long-range drone. The DT46 is a fixed-wing aircraft with removable propellers for optional vertical takeoff and landing (VTOL) capabilities.

Delair’s original battery-powered DT46 can fly for up to 6.5 hours in the fixed-wing configuration or 3.5 hours in the VTOL configuration before needing to recharge. Modified with a hybrid-electric powertrain such as Sterna, the aircraft’s endurance in VTOL mode would extend by nearly 50% to 5.5 hours, according to Ascendance. 

‍“This new version of the DT46 Hybrid UAV will complement our current range of UAVs for long-range inspection missions, both on land and at sea, in both civilian and military contexts,” Delair president Bastien Mancini said in a company statement.

Designed for both civil and military applications, Delair’s DT46 drone has a wingspan of 4.5 meters (15 feet), a payload capacity of 5 kilograms (11 pounds), and a cruise speed of 62 mph. The aircraft itself weighs 25 kilograms (55 pounds) when equipped with the interchangeable vertical lift propellers, which weigh a combined total of about 5 kilograms. 

Ascendance has already conducted hundreds of ground tests of the Sterna propulsion system on an “iron bird” test rig at its test facility near Toulouse, France. The start-up developed the Sterna hybrid-electric propulsion system for its five-seat Atea eVTOL aircraft but designed the system to be modular and scalable for integration with other types of aircraft as well.

“The DT46 Hybrid demonstrates Sterna's ability to adapt to different sizes of aircraft [and] to optimize not only the technical performance but also the carbon footprint for a more sustainable aviation,” said Ascendance co-founder and chief commercial officer Thibault Baldivia.

Having flown several subscale demonstrators, Ascendance is gearing up for the first flight of a full-scale Atea eVTOL prototype by the end of this year. Meanwhile, the first flight of the DT46 Hybrid demonstrator is expected to take place in the first half of the year in Biscarrosse, France.