Regional Turboprops Offer Growth For Bevy Of Technologies

For its future turboprop engines, GE Aviation may ultimately combine technologies evaluated in its RISE Open Fan program—jointly conducted with CFM partner Safran—with hybrid-electric capabilities also under development. An early example of this technology included a 2016 demonstration of a megawatt-class, high-power-density and high-efficiency electrical motor/generator driving an 11-ft.-dia. propeller on a test stand at the company’s Peebles Test Operation in Ohio.

Pratt & Whitney, the dominant player in today’s regional turboprop market, is also working to protect its lead through work with De Havilland Canada to develop a hybrid-electric propulsion demonstrator based on the Dash 8-100. The C$163 million ($127 million) project targets the start of flight tests in 2024 and is a successor to Project 804, an earlier hybrid demonstrator plan that was subsequently sidelined. Ground testing is scheduled for 2022.

Honeywell sees the growing hybrid-electric revolution as a potential opportunity to gain new traction in several markets ranging from long-range advanced air mobility vehicles and next-generation turboprops to larger airliners. The company has started testing a 1-megawatt generator suitable for use in hybrid-electric aircraft that is 2.5 times more powerful than the previous version developed in 2019.

Safran is developing new turboprop technology under Tech TP, a Clean Sky engine-demonstrator project in Europe. First run in June 2019 at Safran’s Tarnos site in France, the engine is now being modified with hybrid-electric elements developed as a subset of the Achieve (Advanced mechatronics devices for a novel turboprop electric starter-generator and health monitoring system) project. Modifications are slated to be completed by the end of the year or early 2022.

NASA’s Pegasus (parallel electric-gas architecture with synergistic utilization scheme) concept—an ATR 42-500-based demonstrator powered by a megawatt-class distributed hybrid-electric propulsion system—could build on technology to be flight-tested under the nearer-term Electrified Powertrain Flight Demonstration (EPFD) project. Targeted at megawatt-class electric aircraft propulsion systems for thin-haul, regional and single-aisle aircraft that could enter service by 2035, flight tests are scheduled to get underway by March 2024.

U.S. startup Universal Hydrogen (UH2) has signed letters of intent with Icelandair Group, Air Nostrum and Ravn Alaska to retrofit ATR 72s and De Havilland Canada Dash 8s with hydrogen fuel-cell propulsion systems. The agreements will see the aircraft’s Pratt & Whitney PW124/127 turboprops replaced with electric motors and fuel cells compatible with UH2’s modular hydrogen system. Flight testing, certification and conversions will be led by aircraft modification specialist AeroTEC. UH2 plans to begin experimental flights in 2023, aiming for supplemental type certification and service entry by 2025.

Deutsche Aircraft, which is working to return the Dornier 328 to production, has partnered with German hydrogen propulsion specialist H2Fly to demonstrate a zero-carbon, fuel-cell-powered version of its revamped 328eco regional turboprop. The 328 demonstrator will be retrofitted with a 1.5-megawatt propulsion system using liquid-hydrogen storage and low-temperature proton exchange membrane fuel cells to generate electricity to power the motor and propeller. Flight tests are due to begin in 2025.

U.S./UK startup ZeroAvia is developing a 600-kW gaseous-hydrogen system for 19-passenger aircraft and plans to convert two Dornier 228s into test airframes. Market entry is planned for 2024. The company is also developing a larger liquid-hydrogen fuel-cell system to power 50-seat-plus regional aircraft, aiming for service entry in 2026.

Under Project Fresson, which is backed by the UK government, Cranfield Aerospace Solutions is converting a Britten-Norman BN-2B Islander to zero-emissions hydrogen-electric propulsion. The nine-passenger aircraft will be test-flown to measure baseline performance with the existing Lycoming O-540 piston engines before retrofit with a pressurized hydrogen fuel-cell propulsion system. Flight tests with the new power train are planned to begin in the first quarter of 2023.

Surf Air Mobility, a Los Angeles-based commuter airline, plans to purchase up to 150 Cessna Grand Caravan EX turboprops from Textron Aviation with plans to convert them into hybrid-electric aircraft for commercial air travel. Following deliveries, scheduled to begin in mid-2022, Surf Air intends to configure the aircraft with its proprietary hybrid-electric power train as a nine-seat variant for use throughout its commuter network on routes of up to 250 nm.