Sikorsky’s Future Family Plans Take Shape Around Electrification

From concepts to demonstrators, Sikorsky is making progress across a wide front as it fleshes out its family-of-systems approach to a future product line of hybrid-electric rotorcraft using common subsystems.

Sikorsky Innovations, the rapid prototyping arm of the Lockheed Martin company, has detailed plans for a range of vertical-takeoff-and-landing (VTOL) platforms, from large uncrewed aircraft to heavy-lift tiltwing transports.

Electrification of rotorcraft is one of Innovations’ three new research thrusts, or pillars. The others include expanding the autonomy of Sikorsky’s platforms and developing larger VTOL uncrewed aircraft systems (UAS).

“We are exploring multiple concepts,” Sikorsky Innovations Director Igor Cherepinsky says. “We call them a family of systems because part of our job at Innovations is not just to design the vehicles themselves or do things like autonomy but also to look at process innovation. How do we deliver these products to our customers faster and cheaper? Part of the way of doing that is to make sure we have a common set of systems that we can develop and use in these different-looking platforms.”

• A hybrid-electric power system testbed is being built
• A medium helicopter and large tiltwing are in conceptual design

Under the VTOL UAS pillar, Sikorsky is flying a 130-lb. model of the rotor blown wing (RBW) platform, a tailsitting flying-wing aircraft—with two dual rotor systems—that transitions from thrustborne vertical flight to wingborne horizontal flight.

Sikorsky is developing a 330-lb. hybrid-electric version of the RBW for DARPA’s Ancillary program for a ship-based, long-endurance UAS. Cherepinsky says the company also is building a 2,000-3,000-lb. aircraft for an undisclosed customer. The concept can scale to 10,000-20,000 lb., he adds.

Innovations is also developing the HEX, a 9,000-lb. gross-weight tiltwing demonstrator with hybrid-electric propulsion. The program has passed its preliminary design review, and Sikorsky is building a power system testbed (PSTB) ground rig that will be used to test the hybrid-electric powertrain.

The 1.2-megawatt series-hybrid powertrain is based on a single GE Aerospace CT7 turboshaft driving a generator that powers Sikorsky-developed 500-kW motors and power electronics driving the dual rotors. Sikorsky plans to power up the testbed by year-end and begin ground runs in 2025, Cherepinsky says.

Two uncrewed HEX demonstrators are being built for the flight-test program that is planned to follow 6-8 months behind the ground testbed, depending on findings from the PSTB, he says. First hover flight is expected in mid-to-late 2025.

A larger four-rotor version of the HEX demonstrator is one of Sikorsky’s first candidate products for a larger hybrid-electric tiltwing aircraft designed for both civil and military uses. “It’s a very efficient hover machine but also a pretty fast aircraft for cargo and people,” Cherepinsky says. “We’ve completed conceptual design and are looking at how all this fits with our production plans.”

Sikorsky also is in conceptual design of a single-main-rotor helicopter with hybrid-electric propulsion. “Hybrid-electric has a nice blend between batteries, conventional turbines and other means for producing power to generate a very low cost-per-flight-hour machine that is eco-friendly,” Cherepinsky says.

In addition to looking at clean-sheet, single-rotor designs with one or two turbine engines, Innovations is actively studying retrofitting hybrid-electric technologies to its existing helicopters. “The S-92 is a great platform for application which we are actively working on,” he says.

With its traditional product focus on medium-to-heavy rotorcraft weighing more than 10,000 lb., Sikorsky sees hybrid-electric propulsion as the best fit in the near term. “Being purely electric for that size isn’t practical yet,” Cherepinsky says.

“Never say ‘never’ . . . but to be pragmatic and be able to develop electrified aircraft architectures, we said we are going to be agnostic to the source of electric power, which today implies the best thing to do is take a turbine and convert all the power to electricity,” he says.

Hybrid-electric propulsion makes sense today and will burn sustainable aviation fuel more efficiently than conventional turbine aircraft, Cherepinsky notes, but it leaves the door open for future energy sources such as solid-state batteries and hydrogen fuel cells.