Hybrid-Electric Helicopters

Say “electric” or “hybrid-electric” engines, and what comes to mind for many is urban air mobility, on-demand air taxis and the 160 companies salivating for a piece of that burgeoning market.

But far from the madding crowd, companies are quietly planning on electric and hybrid-electric engines to increase the transportation capacity of traditional helicopters and make them quieter, more fuel efficient and safer.

“Next year, we will fly an H130 with a 100-kilowatt electric motor and batteries, attributes which will allow much easier autorotation to improve safety,” said Tomasz Krysinski, Airbus Helicopters’ head of research and innovation. “We can also onboard one passenger more due to this extra power. We’re now going through critical design review on the demonstrator.”

Krysinski said that the 100-kilowatt system may see use on helicopters other than the H130.

“The first step is the demonstration to confirm what our theoretical models are telling us,” he said.

Airbus Helicopters is also working on a high voltage “Start and Stop” electric system that should fly next year on the company’s Rapid and Cost-Effective Rotorcraft (RACER) demonstrator. Equipped with Start and Stop, the speedy helicopter will be able to operate at 180 knots with one turbine and then restart the second turbine if necessary.

“The new system allows us to reduce fuel consumption by 20 percent in forward flight to give an 8-ton helicopter 300 pounds of fuel consumption reduction for 400 nautical miles of mission,” Krysinski said. “Hybridization improves productivity for our customers.”

The RACER is based on the X3 prototype aircraft that Airbus rolled out in 2013, a prototype that combined a somewhat traditional helicopter fuselage with stub wings tipped with forward-facing propellers for speedier forward flight. RACER, which may have its debut flight next year, will fly 50 percent faster than a traditional helicopter while burning 25 percent less fuel, according to Airbus. The company is targeting a cruise speed for RACER of 220 knots and a sprint speed of 255 knots or greater.

Mike Mekhiche, deputy director of Rolls-Royce Electrical, said his company is developing “modular and scalable systems that can be used on a number of emerging as well as existing flying platforms encompassing pure electric, hybrid-electric and more electric solutions.”

“Such platforms range from on-demand mobility, also known as personal air mobility, focusing on intra- and inter-city travel — eVTOL and HeVTOL — to general aviation and business/regional type aircraft,” he said. “Range, payload capacity and mission profile all drive the type of propulsion system required for the platform to meet its intended performance requirements, and hence the modularity, scalability and flexibility we are driving into the design of these propulsion systems.”

Mekhiche said that some of the components and subsystems currently under development can be used to provide several performance enhancement features to rotary-wing aircraft.

“For instance, a combination of electric motor, energy storage battery and associated power management and control electronics can provide turbo-boost as well as an emergency landing system to provide the pilot with an effective means to carry out a controlled landing of the aircraft,” he said. “The turbo-boost functionality can support more efficient craft operation.”

United Technologies’ Collins Aerospace said it intends to spend $150 million on electric systems in the next three years. In early April, the company announced it is investing $50 million in a lab in Rockford, Illinois, called The Grid, that will design and test megawatt class motors, power electronics, and generators for electric aircraft for commercial and military purposes. Collins Aerospace said it expects to open the lab in 2021.

One of the first efforts The Grid will support is Project 804, a hybrid-electric flight demonstrator program to mesh the expertise of Collins Aerospace and its sister company, Pratt & Whitney.

While the goal of the project is to re-engine and fly a regional turboprop fixed-wing aircraft powered by a 2 megawatt-class hybrid-electric propulsion system, the lessons from the project are likely to influence Collins’ efforts on electric and hybrid-electric engines for rotorcraft as well.

More fuel efficiency for helicopters may also come from the company’s efforts, using The Grid, to design and test a one-megawatt motor, motor controller, and battery system as the company moves forward on Project 804.

Collins Aerospace said the one-megawatt motor “will be the aerospace industry’s most power-dense and efficient to date, and the new motor and motor controller will be used to assist the demonstrator’s fuel-burning engine as part of its hybrid-electric propulsion system.”

“The Grid will be one of a select few facilities in the world with the capability to test complete electric propulsion systems of this capacity,” according to Collins Aerospace.

At the groundbreaking for The Grid, Collins Aerospace Chief Executive Kelly Ortberg said “Collins is the innovation leader in electric systems, and The Grid positions us to remain the world leader in the electrification of aircraft for decades to come.”

“In the not-too-distant future, hybrid-electric and fully electric aircraft will revolutionize air travel as we know it — opening up new markets like urban air mobility, while re-invigorating others like regional service to underutilized airports,” he said.

Nate Boelkins, vice president of electric power systems at Collins Aerospace, said the company is “exploring potential hybrid-electric and all-electric solutions for rotorcraft and urban air mobility (UAM) platforms.”

“We currently provide the electric power generation system for the V-22 Osprey,” he said. “Hybrid-electric and all-electric propulsion hold significant potential benefits for rotorcraft and UAM platforms, including reductions in noise, fuel consumption, carbon emissions, and operation and maintenance costs.”

“Given the shorter range and smaller size of UAM platforms, we see electrification as viable for them in the near term,” Boelkins said. “For traditional helicopters, the electrification power density challenge can be even more acute compared to fixed-wing platforms since you’re working with a smaller airframe, but still an extremely powerful engine. Thus, we see electrification of traditional helicopters achieving viability in the long term.”

Boelkins said The Grid “will be integral to our efforts to provide electrification solutions for rotorcraft and UAM platforms.”

Safran, which is building the hybrid-electric engine for the Bell Nexus eVTOL vehicle, is also exploring uses for its electric and hybrid-electric engines on traditional helicopters.

While Safran is targeting its ENGINeUS 45 motor for future eVTOL aircraft, the engine may also have uses in traditional helicopters. The engine, which has a continuous power of 45 kilowatts, has built-in, dedicated control electronics with an energy efficiency of more than 94 percent and a power-to-weight ratio of 2.5 kilowatt per kilogram at 2,500 rpm, according to Safran.

The company said that the system’s motor technology consolidates several key conversion, control, and battery interface functions and that the mechanical and structural characteristics are “perfectly suited to aircraft structures.”

ENGINeUS is to include a range of electric motors with a power output of up to 500 kilowatts.

Hervé Blanc, vice president and general manager of the electrical systems and motors division at Safran Electrical & Power, said that ENGINeUS “boasts top-level aeronautical performance from an electromagnetic, thermal and mechanical perspective.”