GE Aerospace Achieves First High-Altitude Hybrid Flight

GE Aerospace announced a series of advancements in hybrid-electric and advanced propulsion technologies at the Farnborough International Airshow, headlined by the completion of the aviation industry’s first high-altitude flight assisted by a megawatt-class hybrid-electric propulsion system.

Conducted in collaboration with NASA, BETA Technologies, and Boeing, the test flight exceeded an altitude of 30,000 feet, reaching standard commercial passenger flight levels. The modified test aircraft, a Saab 340B, sustained hybrid-electric operations for more than two hours during its longest single test flight, marking the longest hybrid-electric flight recorded to date.

The achievement is part of a broader industry effort to develop foundational propulsion components for the eventual successors of narrowbody commercial airliners, such as the Boeing 737 and Airbus A320neo family. Engine manufacturers are seeking to validate technology that can deliver significant reductions in fuel consumption and carbon emissions by the end of the next decade.

Flight Test Campaign and Integration Details

The high-altitude flight tests were enabled through NASA’s Electrified Powertrain Flight Demonstration (EPFD) project, a contract originally awarded to GE Aerospace in 2021 to evaluate the flight readiness of hybrid technologies for single-aisle aircraft.

For the flight test campaign, the right side of the Saab 340B testbed was modified to house a high-voltage hybrid-electric system within an inverted nacelle. The customized nacelle, supplied by Boeing subsidiary Aurora Flight Sciences, features three prominent external inlets designed to provide additional ventilation and cooling.

"This team delivered multiple first-of-a-kind advancements to successfully integrate a high-voltage electrified propulsion system into an aircraft operating at commercial altitudes. Together, we’ve taken a significant step forward in hybrid-electric technology," said Graham Drozeski, Chief Technology Officer, Aurora Flight Sciences. "

The integrated powertrain utilizes a standard GE Aerospace CT7 gas turbine engine paired with an electric powertrain. The system incorporates several specialized sub-components, including:

• Motor/generators, power converters, inverters, and flight controllers developed by GE Aerospace.
• Gearboxes manufactured by Avio Aero.
• Propellers supplied by Dowty.
• Heat exchangers engineered by Unison.
• Torque-sensing mechanisms and dedicated engine wiring harnesses.
• A battery storage system provided by BAE Systems.

During the test flights, which were conducted in the United States by pilots from both GE Aerospace and BETA Technologies, the electric powertrain successfully delivered supplemental power to the propeller and captured generated power to recharge the onboard battery system. Following the US test flights, BETA pilots ferried the modified aircraft across the North Atlantic Ocean to the United Kingdom for its public debut at the airshow, operating the propulsion system in hybrid-electric mode during every leg of the transatlantic journey.

"This hybrid-electric system improved the high-altitude performance and climb capability while creating a flying laboratory to inform all future hybrid designs. The ground and safe flight test campaigns, capped by a flight across the North Atlantic, is the first of many important milestones for hybrid-electric technology," said Kyle Clark, Founder and CEO, BETA Technologies.

Technical Obstacles and Architecture Compatibility

Transitioning hybrid-electric systems from automotive applications to commercial aviation requires addressing specific atmospheric and physics-based challenges. Engineering teams had to design flightworthy components capable of managing high thermal loads, operating under significantly lower atmospheric pressures, and maintaining high power density while meeting stringent aviation safety regulations.

A hybrid-electric engine system operates by combining an electric powertrain with a conventional gas turbine to optimize power management across different phases of flight, such as providing additional thrust during the climb phase to reach cruising altitudes faster. According to GE Aerospace, these electrified systems are highly compatible with alternative fuels and alternative engine architectures, specifically Open Fan designs.

Unlike traditional ducted turbofan engines, an Open Fan architecture utilizes one rotating front fan and a second stationary row of outlet guide vanes to direct airflow. This design removes the heavy outer engine casing, which significantly increases the propulsive efficiency of the engine.

Alex Simpson, leader of Open Fan and compact core engineering development at GE Aerospace, stated that the Open Fan design was selected over alternative next-generation concepts because it provides a substantial increase in fuel efficiency alongside enhanced component durability.

"To get a 20% reduction in fuel burn, you have to change something pretty significantly. Open Fan architecture is the only architecture that can get you the gains we’re after," Simpson said.

Strategic Programs and Long-Term Roadmap

The hybrid-electric and Open Fan systems are core pillars of the Revolutionary Innovation for Sustainable Engines (RISE) program. Managed by CFM International, a 50-50 joint venture between GE Aerospace and France's Safran Aircraft Engines, the RISE program is a comprehensive technology demonstrator aimed at reducing fuel burn and carbon dioxide emissions by more than 20% compared to current commercial engines in service. To date, the RISE program has completed approximately 500 test campaigns and logged more than 3,000 endurance cycles across its suite of technologies, which also includes "compact core" designs for smaller, highly efficient engine cores.

The high-altitude flight represents the culmination of a decade-long testing roadmap detailed by GE Aerospace:

• 2016: Conducted initial ground testing of an electric motor-driven propeller.
• 2022: Completed the first test of a megawatt-class, multi-kilovolt hybrid propulsion system under simulated altitude conditions up to 45,000 feet at the NASA Electric Aircraft Testbed.
• 2025: Formed a strategic partnership and equity investment with BETA Technologies to co-develop a hybrid-electric turbogenerator for Advanced Air Mobility (AAM) applications.
• 2025: Demonstrated a narrowbody hybrid configuration utilizing power transfer and injection within a modified high-bypass turbofan engine without requiring an energy storage system, under the NASA HyTEC project.
• 2026: Finalized ground testing of the megawatt-class EPFD propulsion system, clearing the way for the high-altitude flight trials.

Industry Context and Market Dynamics

As GE Aerospace presents its data at Farnborough, competing engine manufacturers Pratt & Whitney and Rolls-Royce are scheduled to provide updates on their respective next-generation propulsion research programs.

While the test flight establishes physical viability, the commercialization of hybrid systems faces scrutiny regarding weight penalties. Industry sources indicate that Boeing has expressed concerns regarding the total weight of commercial-scale hybrid systems, highlighting the structural implications of required components such as the three additional cooling inlets displayed on the Saab 340B nacelle. Furthermore, Boeing has historically signaled less willingness than its European rival Airbus to adopt un-ducted Open Fan designs for future aircraft platforms.

Addressing the trade-offs of the technology, Mohamed Ali, President and CEO of GE Aerospace Commercial Engines & Services, noted that balancing weight and operational performance is a standard component of commercial engine design. While Ali declined to specify exactly how the high-voltage system would be integrated into a finalized commercial product line, he affirmed its strategic value.

"Simulation has given way to real world innovation," Ali stated. "This certainly would become a significant enabling technology. By flying a hybrid electric engine system at altitudes never achieved before, we’re proving to our customers and to the industry the advanced capabilities we can bring to next-generation aircraft with ready technologies."

The modified Saab 340B aircraft is scheduled to remain on static display during the mornings at the Farnborough International Airshow and will participate in public demonstration flights during the daily afternoon flying schedules. GE Aerospace plans to transition the data and lessons learned from the Saab 340B campaign toward future testing phases, which include plans to test Open Fan architecture and other RISE program technologies utilizing GE Aerospace’s dedicated 747 Flying Test Bed facility in Victorville, California.