Now well into its sixth decade in production, Britten-Norman’s Islander family of utility aircraft probably isn’t many people’s idea of the future of air transportation. But for the companies involved in the UK’s Project Fresson, the versatile workhorse is an ideal platform for a hydrogen-powered, zero-carbon regional airliner capable of carrying nine passengers on short-haul routes that are hard to serve with larger aircraft.
In late October, propulsion innovator Reaction Engines became the latest supplier to join a consortium of companies led by Cranfield Aerospace Solutions as it aims to achieve service entry of the green Islander in 2025. It will provide fuel cell cooling technology to work with the hydrogen fuel cell system being provided by Ricardo UK and fuel tanks from Innovatus Technologies to contain the gaseous hydrogen.
According to Cranfield’s chief strategy officer, Jenny Kavanagh, the Islander represents phase one on a Project Fresson roadmap that aims to advance hydrogen propulsion to the point where it could power airliners carrying up to 100 passengers. Converting an as-yet-unspecified 19-seater is the consortium’s likely next step, but for now, it sees plenty of commercial potential in the Islander, with its short takeoff and landing performance making it ideal for remote communities that depend on low-volume air links.
The choice of hydrogen as the fuel source marks a change of course for Project Fresson, which had earlier won UK government support to develop a hybrid-electric propulsion system, for which Rolls-Royce had been a partner. "We quickly worked out that the batteries were not powerful enough for the performance needed from this size of aircraft," Kavanagh explained. "It's a question of horses for courses when it comes to the choice between electric or hydrogen."
The program’s launch customer, the Isles of Scilly Steamship Group (ISSG), has long used Islanders on its Skybus flights connecting the archipelago to the UK mainland 30 miles away. It views the hydrogen-powered conversion as an ideal alternative to far slower ferry services or helicopters. Currently, Islanders are powered by a pair of piston or turboprop engines, provided respectively by Lycoming and Rolls-Royce.
Kavanagh told FutureFlight that using a well-established airframer like the Islander greatly simplifies the certification process, allowing the partners to “change as little as possible,” in order to earn the required supplemental type certificate. Another advantage is that more than 750 of the aircraft are still in service worldwide, presenting ample opportunities to market the conversion program.
Last week, Britten-Norman announced that it is looking to acquire preowned aircraft from its existing operators. The Isle of Wight-based business will develop the required changes to the airframe’s design, both for the conversion and possible new-build hydrogen-powered models.
“Many Islander flights are lifeline routes covered by PSOs [government-funded Public Service Obligation contracts], where there are no [land-based] alternatives,” Kavanagh commented. She challenged the growing assumption that short-haul domestic air services should give way to alternatives like new and improved rail links, arguing that zero-carbon sub-regional aviation should be a key part of future transportation systems.
The Project Islander partners have yet to announce the choice of supplier for the electric motors to be integrated with the fuel cell system. Denis Ferranti, one of three partners investing in project Fresson, says it is providing a fully integrated electric propulsion unit, including motors, converters, and gearbox.
Cranfield is acting as systems integrator, and Britten-Norman will provide an airframe for a prototype that the consortium aims to start flight testing in 2023. With detailed design and systems integration now well underway, next year should see the start of bench and ground testing of the powertrain.
The full performance and specifications for the hydrogen-powered Islander have yet to be confirmed. Kavanagh indicated that Project Fresson is targeting the same payload of up to nine passengers as the existing aircraft, albeit with a reduced range of around 150 miles, which is about a quarter of the current aircraft’s limits (allowing for emergency power reserves). The aircraft is expected to need little more than 700 feet of runway from which to operate.
Cranfield, which is a wholly-owned subsidiary of specialist aerospace school Cranfield University, harbors ambitions to be an airframer, developing and potentially building new aircraft. In Kavanagh’s view, apart from the environmental objectives, Project Fresson has wider significance in the context of the long-term future of the UK aviation sector.
“We see a threat to UK aerospace companies, and especially those supplying aircraft parts and subassemblies,” she said. “There is a danger that the supply chain could be lost and this is a perfect opportunity [to reverse that trend].”
In her view, smaller start-ups like Cranfield, which is seeking further investment support, and its partners are better placed to advance these opportunities than larger aerospace ventures. “It’s down to whoever has the passion, experience, and willingness to work with others,” she said. “Big companies can find it hard to disrupt their current business model when they’ve got all that revenue flowing from existing products.”