NASA GL-10 Greased Lightning

Lore & Background

The GL-10 Greased Lightning is a tiltwing unmanned aircraft that uses a hybrid diesel-electric propulsion system. Its wing carries eight electric motor-driven propellers, while the horizontal stabilizer has two. In the planned full-scale version, power is generated by two 6 kW diesel engines that charge lithium-ion batteries. The propellers on the leading edge of the wing provide high-speed flow and lift even at low forward velocity, giving pitch, roll, and yaw control authority during the critical transition from hover to forward flight. The propellers are designed for a relatively low tip speed, resulting in a marked reduction in noise. The aircraft performed transitions between vertical and horizontal flight in 2015.

Reader's Guide

The GL-10 Greased Lightning represents a class of UAV that eliminates the requirement for additional ground support equipment such as launch catapults and landing catch mechanisms, thanks to its VTOL capability. Its design allows it to complete several vertical take-offs and landings during a single mission, with a loiter endurance of 24 hours in forward flight mode. The aircraft was followed by the Langley Aerodrome No. 8 (LA-8), a tandem-wing, deflected-slipstream design with four propellers on each wing, tested in a Low-Speed Wind Tunnel before flight tests in late August 2019. The GL-10 is listed alongside other notable tiltwing and VTOL aircraft such as the Canadair CL-84 Dynavert, Hiller X-18, and LTV XC-142, and is included in the list of electric aircraft.

Did You Know?

• The GL-10 has eight propellers on its wing and two on its horizontal stabilizer.
• Its full-scale version uses two 6 kW diesel engines to charge lithium-ion batteries.
• The propellers are designed for low tip speed to reduce noise.