Story ID: 080
Manufacturer Focus Shifts To Sustainable Aviation Imperative
By: AIN Staff
Caption: Companies such as Rolls-Royce, GE Aviation, Pratt & Whitney, Collins, and CAE, to name a few, are forging ahead with sustainable technologies.
Word Count: 2054
Rolls-Royce CEO Warren East calls a focus on sustainable aviation “an absolute necessity and a commercial imperative” but added it also represents an opportunity. “That is the approach we are taking,” he said during the recent Farnborough Airshow.

This sentiment has spread throughout the industry with companies representing all sectors of civil aviation pressing ahead and investing substantially to develop new technologies to move the industry away from its reliance on petroleum.

This was readily apparent during the Farnborough Airshow, where sustainability quickly became a theme throughout an event that typically is focused on a bevy of orders. And while the orders were certainly there, companies such as Rolls-Royce, GE Aviation, Pratt & Whitney, Collins, and CAE, to name just a few, all showcased their progress on new sustainable programs.

Rolls-Royce is eyeing multiple technologies from hydrogen power and continues research into hybrid-electric. The engine-maker also is planning a series of rig and engine tests to prove that 100 percent sustainable aviation fuel “can safely and efficiently deliver power for small-mid size aircraft from the mid-2030s onwards,” it said. “We have further ambitions to move this on to a flight test phase as part of the program in the long term,” it added.

Rolls-Royce has already carried out several hydrogen combustion tests along with Loughborough University, German research institute DLR, and Cranfield University. Plans call for two ground tests to take place on a Rolls-Royce AE 2100 turbine engine in the UK this year and with a Rolls-Royce Pearl 15 jet engine in the near future. The company is considering a range of locations for the trials, including its test facility in Mississippi.

The London, UK-headquartered company, which has divisions in civil aerospace, defense, power systems, and electrical, said it closely followed market research carried out by the UK Aerospace Technology Institute’s Fly Zero team and Project Napkin (New Aviation Propulsion Knowledge and Innovation Network). Both organizations concluded the existence of market potential for hydrogen-powered aircraft.

Rolls-Royce is also working with EasyJet on hydrogen infrastructure, as well as Norway-based regional airline Widerøe and Brazilian OEM Embraer, on hybrid-electric and hydrogen power systems for a regional aircraft research project already underway.

Tests in Bristol, UK, and Trondheim, Norway, have confirmed that Rolls-Royce’s Power Generation System 1 (PGS1) demonstrator, which incorporates an AE 2100 engine and special controls and thermal management systems, delivered more than 1.5 megawatts of power. “This is the first time this has been achieved in the aviation sector,” the company said. As a result, Rolls-Royce is considering how it could achieve a production version of PGS1 and discussing airframers’ future requirements for such a propulsion system.

“We are pioneers of power and this program puts us in a great position to pave the way to make hydrogen and hybrid-electric systems a reality,” said Chris Cholerton, president of civil aerospace. “Combined with our work on sustainable aviation fuel and further gas turbine efficiency, we are making real progress on the hard yards of research and development towards making net-zero flight a reality.”

Rival GE Aerospace is also working on multiple fronts and has achieved a first in the area of hybrid-electric.  In a partnership with NASA and Boeing, GE Aerospace has successfully completed for the first time, testing involving a megawatt-class, multi-kilovolt hybrid-electric propulsion system in simulated altitude conditions for single-aisle commercial flight.

These tests pave the way for preparation to fly a hybrid-electric propulsion system on board an aircraft testbed later this decade.

Beginning a little more than a year ago and running through earlier this year at NASA’s Electric Aircraft Testbed (NEAT) facility in Sandusky, Ohio, the test marked the culmination of more than a decade’s worth of research and marks a key milestone in the effort to bring hybrid-electric propulsion to single-aisle aircraft in the mid-2030s.

Involving a complete high-power, high-voltage system, including electric motor/generators, power converters, power transmission, and power control systems, the test demonstrated the performance and operation of components in flight environments up to 45,000 feet. Two sets of a hybrid-electric system were operated to represent the right and left aircraft engines.

The components were tested independently and as an integrated system with evaluations covering multiple modes, including power transfer from side to side, power assist to a simulated engine, and aircraft power generation. The trials also involve simulation of energy storage.

Mohamed Ali, v-p and general manager of engineering for GE Aerospace, noted the test managed to overcome a key barrier for use of hybrid-electric in regional and single-aisle aircraft—flight above 10,000 feet with higher voltages. At higher altitudes, plasma arcing becomes an issue when involving high-voltage systems, due to the thinner air causing reduced resistance. “You need to invent technology to prevent that,” he said, as well as handle thermal management.

Ali called the effort a building block toward hybrid-electric and said it is one of many ahead in the journey toward hybrid in commercial flight.

Testing will continue under NASA’s Electrified Powertrain Flight Demonstration program with a flight test later in the decade of a hybrid-electric system involving CT7-turboprop-powered Saab 340 aircraft.

Brian Yutko, v-p and chief engineer of sustainability and future mobility at Boeing, said the company has acquired the aircraft and begun modifications. Boeing unit Aurora Flight Sciences works with Boeing on the integration. The teams are preparing the systems for flight and will prove flight worthiness and safety for the experimental flight tests.

Meanwhile, Raytheon Technologies' sister companies Collins and Pratt & Whitney are collaborating on a new hybrid-electric technology demonstrator program for future advanced air mobility (AAM) vehicles. The Scalable Turboelectric Powertrain Technology (STEP-Tech) demonstrator will focus on developing high-voltage distributed hybrid-electric propulsion concepts in the 100- to 500-kW class, with the potential to scale to 1-MW and beyond. The modular demonstrator platform enables rapid prototyping of a wide range of configurations, the companies said, and plans call for ground testing to begin late this year.

“Our employee base, who love to connect and protect the world through aviation, are very excited to be working on sustainability today,” said Collins chief sustainability officer LeAnn Ridgeway.

Ridgeway and Graham Webb, her counterpart at P&W, reviewed the technology and “basket of measures” they are developing to support the aviation industry’s goal of achieving carbon-neutral operations by 2050. Air traffic modernization products, for example, allow route and operations optimization; lighter-weight materials cut fuel consumption; engines that can burn 100 percent sustainable fuels reduce CO2 emissions; and hybrid-electric and hydrogen propulsion concepts in development promise to complete the last mile on the journey to net zero.

Those propulsion programs include P&W’s Hydrogen Steam Injected, Intercooled Turbine Engine (HySIITE) project, which uses liquid hydrogen combustion and water vapor recovery to produce zero in-flight CO2 emissions and an 80 percent reduction in nitrogen oxide (NOx) emissions while reducing fuel consumption some 35 percent. Earlier this year, the U.S. Department of Energy selected P&W to develop hydrogen propulsion technology for commercial aviation.

Collins also designed a 1-MW electric motor for P&W’s regional hybrid-electric flight demonstrator, which will re-engine one of the powerplants on an experimental de Havilland Dash 8-100 regional turboprop, augmenting its turbine engine with the electric motor in a parallel hybrid configuration. The electric motor will provide extra power during takeoff and climb, allowing the fuel-burning engine to be optimized for cruise flight, and yielding an expected 30 percent improvement in fuel efficiency and a corresponding reduction in CO2 emissions. The company has scheduled flight tests of the hybrid-electric demonstrator for 2024.

Other suppliers, such as GKN Aerospace, are working toward future possibilities such as hydrogen. Working with multiple partners, the aerostructures and engine components specialist says it has made important discoveries from both the H2Gear and H2Jet programs, which respectively focus on hydrogen-electric fuel cell-based powertrains and direct combustion of liquid hydrogen fuel in turboprop and turbofan engines.

According to chief technology officer Russ Dunn, GKN and its partners expect to have completed the preliminary design for a hydrogen-electric propulsion system by the end of this year. “We have defined the architecture for a number of different aircraft with 19, 48, and 96 seats, and it scales [up in size] really well and actually becomes more attractive than we thought for larger aircraft,” he said.

From GKN’s perspective, failure to decarbonize flights is not an option for the air transport industry. Dunn said that aviation’s portion of global emissions will inevitably rise in the coming years as flight volumes increase and other industries reduce their emissions. “If we don’t do this, we’ll see a suppression of global flights through measures that we don’t want, such as taxation, so it is in our interests to ensure we can achieve sustainable growth,” he said.

The UK-based H2Gear team endeavors by next year to attain technology readiness level (TRL) 4 and complete testing of the cryogenic electric motor and fuel cells. The following year should see the start of sub-system detailed design and testing as the program reaches TRL5 and then in 2025 the culmination of work with ground-based testing of a full system-level propulsion system.

Work on the £54 million project takes place at GKN’s Global Technology Center in Bristol, UK. With government funding behind it, the partners include fuel cell specialist Intelligent Energy, electric motors and control systems group Aeristech, Newcastle University, the University of Manchester, and the University of Birmingham.

At the smaller end of the market, hybrid-electric also is making significant strides. In fact, training and simulation specialist CAE has partnered with Piper Aircraft to develop a supplemental type certificate (STC) for an electric powerplant conversion of the single-engine Piper PA-28-181 Archer light airplane. Under the partnership, Swiss company H55, which provided technology used on the Solar Impulse sun-powered world-rounding airplane, will supply the battery system for the STC. Safran Electrical & Power will supply its EngineUs 100 electric motor that provides a maximum of 150 kW power at takeoff and incorporates an integrated motor controller.

The project draws support from a Project Resilience program under which CAE plans to invest C$1 billion over the next five years in innovation through a partnership with the governments of Canada and Quebec.

CAE president and CEO Marc Parent said the project combines CAE’s “innovative spirit and our commitment to sustainability” and comes as the company celebrates its 75th anniversary. As for the move to electrify the Piper, he noted that new propulsion technology stimulated development over the history of aviation. "We’re seeing it here today," said Parent. "This is a leap forward for CAE.”

Noting that Piper has produced more than 28,000 Archers, Parent added that selecting that model made sense for CAE because it is one of the largest operators of the Piper aircraft. “We literally have hundreds of aircraft and a big portion is Piper Archer aircraft,” he said.

As such, he added Piper is “absolutely positioned to bring in leaders in electrification together…to develop a modification for the aircraft." Parent added the modification will be important for CAE not only in making its training more sustainable but also in helping to train students on the operation of electrical aircraft, which he sees as an important need for the future.

However, plans call for CAE to make the STC available not only for its flight schools but to other operators worldwide. Under the agreement, Piper would have the ability to leverage the STC for its other products and into the production line. Ron Gunnarson, v-p of sales, marketing, and customer support for Piper, said that the approach is similar to the one it took with the Continental CD-155 engine that can run on diesel or jet-A and is offered in an Archer airframe. He added that the company plans to move forward with such evaluations.

Parent was not yet ready to reveal a timeline for the project, only saying, “We’re not talking years.” Pricing is still to come as well.