Executive Summary
Aviation’s path to decarbonization is accelerating, and one of the most promising near-term opportunities lies in retrofitting existing regional aircraft with hydrogen fuel cell systems. The ATR 72—a 72-seat turboprop already used widely for short-haul routes—is emerging as a key candidate for early adoption. This story explores the technical, economic, and regulatory dimensions of converting turboprops from fossil fuels to zero-emission hydrogen power. Despite a recent partner setback, project leaders remain committed, pointing to a future where quiet, clean regional flight becomes a commercial reality before 2030.
This next web story will cover Entry into Service – retrofitted regional turboprops, which will be powered by hydrogen fuel cells. This idea has been proposed in the IATA Net Zero Technology Roadmap and is indicated in Figure 1 as item 8. The timeline for this event is stated to be between 2025 – 2030.
Figure 1: IATA Net Zero Roadmap, SAF & Hydrogen Aircraft
Given the smaller sizing’s of the proposed turboprop aircraft candidates and a few related issues dealing with fitting a Hydrogen Fuel Cell into the aircraft candidate, a key initial decision here was to assign as a long term consideration, the use of the Hydrogen Fuel Cell (HFC) technology to regional flights.
A key airframe candidate for initiating this project is the ATR 72 (see Figure 2). As the number in its name indicates, it is a 72-seater. Because of its size and general adaptability, this airframe has been used for other test programs in the past and is also part-owned by Airbus, which is a project participant.
Figure 2: The ATR 72, an early candidate for the decarbonization of aviation
Other aerospace development-oriented companies, such as ZeroAvia, are also participating in this project. ZeroAvia indicates that it is committed to the development of full hydrogen-electric engines for existing commercial aircraft and also supplying hydrogen and electric propulsion component technologies for these and related applications.
As with many aerospace development projects, the financial support needed to support such projects is considerable. Partners need to have the financial resources to sustain themselves for at least the mid-term. In this case, one of the project’s early partners has declared bankruptcy. This partner was responsible for developing the hydrogen refueling systems (i.e. ground facilities) and airplane conversion retrofit kits.
Despite the departure of one important partner, this transatlantic project will continue, ultimately in some form or other, as the senior project partners are still committed.
Conversion of an airplane from an internal combustion turboprop to a fuel cell setup calls for a series of changes and considerations, some of which are indicated as follows:
- Propulsion System: The existing Pratt & Whitney turboprop engines need to be replaced with electric motors that are now powered by hydrogen fuel cells.
- Hydrogen Storage: Liquid hydrogen (LH2) or compressed gaseous hydrogen (GH2) (i.e. the fuel) is stored in tanks that are typically integrated into the aircraft’s fuselage, requiring removal of some seating.
- Challenges: Achieving comparable reliability to existing gas turbine jet engines is a key consideration. Also the significant reduction in payload capacity and range due to hydrogen storage, along with the availability and cost of green hydrogen are ongoing challenges.
- Regulatory Progress: The FAA will require a Supplemental Type Certificate (STC) approval necessary for ATR 72 conversions which is an important process that needs to be managed.
Unlike Jet fuel (A or A-1), which is stored in the wings of aircraft, this cannot be accomplished when using hydrogen storage tanks. The storage problem for hydrogen arises because it must be stored in high-pressure gas cylinders or cryogenic liquid hydrogen tanks, both of which are generally bulky. These tanks (see Figure 3) take up space and will displace some passenger capacity.
Figure 3: Bulk Hydrogen storage containers for aviation applications
Benefits of Hydrogen fueled aircraft
The potential benefits of zero-emission flying come from the fact that hydrogen fuel cells produce only water vapour as a byproduct. Traditional emissions of CO2, NOx, and fine particle emissions arising from gas turbines are no longer produced. Furthermore, hydrogen-powered aircraft are expected to be quieter than traditional aircraft. And lastly, retrofitting existing aircraft with hydrogen fuel cell technology offers a relatively near-term pathway to decarbonizing the aviation sector. As indicated earlier, the ATR 72 is a regional aircraft with a range of about 1400 km. With the conversion to hydrogen fuel cell power, this plane’s capacity is claimed to be minimally impacted, with an indicated reduction to 72 seats from the original design of 78 seats.
Fuel Cell Considerations
Having raised the hydrogen fuel cell several times over our previous stories on the EnviroTREC website, we will now discuss some unique considerations respecting the deployment of the hydrogen fuel cell for aviation applications.
The reaction of hydrogen and oxygen to form water releases significant energy. Hydrogen fuel cells harness the energy that is released in this chemical reaction and generates electricity. While there are a few different architectures of fuel cells, the proton exchange membrane fuel cell (PEMFC) is currently the prevalent architecture in road vehicles and is the likely the one to power aviation. Figure 4 shows a general diagram of the PEMFC.
Figure 4: The Fuel Cell
An individual fuel cell unit refers to a single set of catalyst electrodes, electrolyte, and gas delivery layers that can produce electricity by harnessing the energy released when hydrogen and oxygen combine to form water.
However, individual fuel cell units cannot produce much power, so they need to be combined to generate sufficient electricity to operate, in this case, an airplane. Accordingly, hundreds of fuel cell units will need to be assembled together to form a fuel cell stack.
Operating a fuel cell safely and reliably requires auxiliary systems in addition to the stack itself. These additional systems are referred to as the balance of plant (BoP), and these include thermal management, gas delivery, water exhaust, and electrical systems, which are also indicated in Figure 4.
When combined, the fuel cell stack and BoP create the fuel cell system. This is now a complete electricity generation machine that will be placed in the ATR 72.
Based on input from industry experts, fuel cell technology still requires several years to mature in its capability before being used in the desired aerospace application.
As an example of the current technology gap, aircraft fuel cells will need to output around 50 times the power of an automotive fuel cell before they can be commissioned. It is assumed that the larger scale of aircraft fuel cells will result in better performance metrics. These high values represent ambitious targets which will require technological breakthroughs from possibly a variety of new research sources.
Hydrogen Fuel Cell Life Cycle Considerations
Hydrogen fuel cells also present with their own unique life cycle considerations which need to be understood and managed. Hydrogen fuel cells would likely need to be replaced several times within the lifetime of a retrofit aircraft. Current automotive fuel cells are designed to last for 5,000 hours of operation. The aspirational target, set by the U.S. Department of Energy (DOE), for the lifetime of a fuel cell is 8,000 hours.[1] As a reference, a 700-km-long flight on a turboprop aircraft takes about 90 minutes. If an aircraft makes four daily flights (two round-trip flights), its fuel cell would have to be changed in about 3.5 years. As a comparator, an aircraft’s typical lifespan is 25–30 years, which would indicate that 7–9 fuel cell replacements will be needed during its lifetime. These fuel system swap downtimes will now take the entire aircraft out of service and will reduce its earning potential.
Hydrogen Challenges
Earlier in the story, it was indicated that hydrogen refueling challenges were found. The hydrogen industry is currently nascent, which is generally comprised of new entrants and a lack of business demand. Capital investment funds are also lacking, and economic incentives are absent, which are commonly used to mobilize growth.
The hydrogen economy does not exist, although it is somewhat understood. While hydrogen holds promise for decarbonization in various sectors, challenges remain in its production, storage, and distribution. The current hydrogen industry is largely focused on specific applications like industrial feedstock and ammonia production.
Specifically, while there is a projected growth in the global hydrogen market, particularly for clean hydrogen, the current infrastructure and production capacity are not sufficient to meet a widespread hydrogen economy. The hydrogen that is currently required is produced from natural gas. This process releases greenhouse gases and is referred to as blue hydrogen. The aviation market over the long term market would require green hydrogen which would most likely be produced from solar, wind, hydraulic or even nuclear power.
A comprehensive hydrogen economy requires significant investment in new infrastructure for production, storage, and distribution, including pipelines, specialized trucks, and ships. Lastly, storing and transporting hydrogen, especially at scale, presents technical challenges, including the need for high-pressure tanks or liquefaction, which adds to the cost of the final product.
Concluding overview
Retrofitting regional aircraft like the ATR 72 with hydrogen fuel cell systems remains a promising and technically viable step toward decarbonizing aviation. While this TP HFC project has faced a significant setback with the loss of a key partner, the remaining stakeholders are well-positioned to carry the concept forward. Hydrogen fuel cells offer an emissions-free propulsion pathway and may become economically competitive as green hydrogen production scales up. In the interim payload and range trade-offs, infrastructure gaps, and lifecycle considerations must still be resolved.
The project serves as a crucial testbed for not just technical feasibility but also market readiness and ecosystem support. As new partners are secured and regulatory pathways firm up, this effort could become a cornerstone in the early adoption of zero-emission regional flight—delivering real impact well before 2030.
[1] Development of Targets for Heavy Duty Fuel Cell Vehicles with Application-Driven System Modelling – IOPscience