Airbus has turned to aircraft engines group CFM International to be its propulsion partner for the planned ZEROe hydrogen-powered airliner it aims to bring to market in 2035. The companies on Tuesday announced plans to convert an A380 aircraft with a hydrogen powertrain that would drive a GE Passport turbofan by the end of 2026.
The demonstration will use the first A380 prototype as the flying testbed, equipped with four tanks holding 400 kilograms of liquid hydrogen stored near the back of the airplane’s interior. Airbus, which in September 2020 announced plans to evaluate three potential ZEROe designs, said it will define the hydrogen propulsion system requirements, oversee flight testing, and provide the A380 platform to test the hydrogen combustion engine in the cruise phase of flight.
CFM, which is a joint venture between GE Aviation and Safran that supplies turbofans for multiple Airbus and Boeing airliners, has agreed to modify the combustor, fuel system, and control system of a GE Passport turbofan to run on hydrogen. The partners chose the engine for its physical size and light weight, as well as its turbomachinery and fuel flow capability. Plans call for Airbus to mount the engine on the upper fuselage of the A380, just ahead of the tail, to allow for monitoring of engine emissions separately from those of the engines powering the aircraft. CFM will execute an extensive ground test program ahead of the A380 flight test starting this year.
Airbus chief technical officer Sabine Klauke explained that engineers will surround the four hydrogen tanks with a hermetically sealed container for safety. The partners chose the A380 as the test platform for its large size, which will allow flexibility for installing all the various systems and pipes needed to allow for efficient conversion of the liquid hydrogen to gas for the Passport engine’s combustor.
Some of the technical hurdles, Klauke added, center on the fact that hydrogen burns 10 times faster than jet fuel, raising challenges involving the stability of the flame. Safran chief technical officer Michel Brioude explained that additional challenges surround the need for cryogenic fuel pumps and new piping and seals to accommodate the very cold temperatures—as low as -250 deg C—with which the hydrogen must be stored in its tanks. Meanwhile, the process of converting liquid hydrogen into gas will require “a very different” heat exchanger than what conventional systems use today.
“There are many technical issues but I can tell you we are committed and confident that we will address them,” said Brioude. “On the other side, during the flight test program, what we want to characterize is the condensation trails produced by the engine in different atmospheric conditions. As you know, hydrogen does not produce CO2, but it produces three times more water emissions. So those kinds of condensation trails might be a contributor to the greenhouse effect. Today, we don’t know how long it lasts in the atmosphere, so we need to do the tests [and] collect the data to be able to know the [effect on] climate change.”
The executives, who had gathered for a press briefing in Toulouse and Washington, D.C., declined to quantify the level of research and development spending the program will need. CFM chief executive Gael Meheust said the investment would fit into his company’s current R&D spending plan and expressed optimism in the interest the European Union and the French government have shown in hydrogen propulsion. “So can also have hope to have support [from governments], he said.
“Hydrogen combustion capability is one of the foundational technologies we are developing and maturing as part of the CFM RISE Program,” said Méheust. “Bringing together the collective capabilities and experience of CFM, our parent companies [GE and Safran], and Airbus, we really do have the dream team in place to successfully demonstrate a hydrogen propulsion system.”
In terms of regulatory considerations, GE Aviation’s engineering division vice president and general manager Mohamed Ali spoke of the need for partnerships across the industry, including with regulators to build a framework to meet safety standards expected by the public. He stressed GE’s already substantial experience with hydrogen—the company has collected more than 8 million hours of experience running ground-based hydrogen gas systems—as evidence of its ability to safely test such technology. “So we know how to put the safety precautions around that, and all of these learnings would be taken into the future testing of this program,” he explained.
Brioude said the partners have already “touched base” with EASA and the FAA to explain the technical challenges and understand the regulatory requirements for ensuring the platform can fly safely and start to define the key points for earning certification. “So we have data, we have experience we can share with them,” he noted. “But they are very open-minded about working with us.”