- 23 Dec 2021
- Patrick Ryan
- Multi-Mission Aircraft
What will propel General Aviation aircraft in the future? Hydrogen, hybrid-electric or purely electric, or will it still be piston engines? The answer to this question is an exciting one...Back to Articles
When considering future propulsion methods for General Aviation aircraft, one thing is certain: Whichever type of propulsion system prevails, it will have to be sustainable...
Global aviation has committed to drastically reducing its emissions and even becoming largely climate-neutral between 2040 and 2050, even though it only accounts for a low single-digit percentage of global CO2 emissions. And of total aviation emissions, General Aviation in turn accounts for only an extremely small percentage.
The technological challenges facing engineers and designers to achieve this ambitious goal are daunting. But the potential lurking in the conversion of propulsion technology for General Aviation is huge for all stakeholders.
General Aviation has very long innovation cycles, not only because of the large investments that go into the development, certification, and purchase of new aircraft – which take years to recoup – but also because it has achieved a very high standard of safety.
A new technology must first achieve this level of reliability and safety, because even when new products are introduced, safety is without a doubt the top priority in aviation. No one will buy and use a new aircraft that offers worse safety standards than the tried-and-tested models.
Today’s internal combustion engines have proven their worth, are reliable, and will undoubtedly continue to be found in General Aviation aircraft for decades to come. But they will face strong competition, even if it is not yet clear today which new propulsion technology will prevail on the market.
On the one hand, there is the idea of powering GA aircraft in the future with electric motors that draw their energy from batteries. Various companies are pursuing this concept with increasing success.
With the Pipistrel Velis Electro, EASA (the European Union Aviation Safety Agency) already certified the world’s first purely electrically powered aircraft, in June 2020. It has a maximum take-off weight of 600 kilograms and, at 10.50 meters, the same wingspan as the Pipistrel Virus SW 121 from which it was developed.
The 100 hp (74 kW) Rotax 912S3 internal combustion engine of the Virus has been replaced by a 57.6 kW Pipistrel E-811-268MVLC electric motor, which achieves a continuous power of 49.2 kW at 2,350 rpm.
Various institutions and organisations such as the French FFA (Fédération Aéronautique Française), the Royal Danish Air Force, and the Westflug flight school in Aachen (Germany) are either already operating it or want to test the prototype for its suitability in pilot training. Greenlease Aero from France wants to make it easy for aeroclubs to operate the Pipistrel electric aircraft. The company has ordered 50 of the Velis and plans to lease them to aero clubs. The British Green Airside initiative is also pursuing a similar business model and wants to buy up to 50 Velis Electro to lease to flying schools.
Electric aircraft promise significantly reduced operating costs compared to aircraft with conventional piston engines. They are also quieter in flight.
As a result, they offer flight schools and clubs the potential to appeal to a larger target group, as the cost of flying is significantly reduced.
But there are two sides to every coin: The low cost and environmental friendliness of electric flight is currently still countered by the energy density of today’s batteries: electric aircraft are currently always very short-range aircraft and lag far behind their combustion counterparts in terms of range.
Without dramatic leaps in battery technology, all-electric aircraft will have to stay close to the airfield, as they will already run out of energy after just under an hour of flight time (if that).
But battery manufacturers around the world are working on this issue, as electric cars also need efficient and fast-charging energy storage systems, and are accelerating research into efficient, high-capacity batteries.
Another hurdle for any new type of propulsion is also the infrastructure at airports, which still has to be built, regardless of whether aircraft will fly with batteries or hydrogen in the future. The necessary charging and refueling infrastructure is still lacking today and requires significant investment from the airports and energy providers for alternative types of propulsion.
Bye Aerospace, based in Colorado, USA, is currently working to get its eFlyer 2 two-seat electric aircraft certified by the U.S. Federal Aviation Administration (FAA).
Founder and CEO George Bye selected the ENGINeUS 100 electric motor from French manufacturer Safran Electrical & Power as the propulsion unit.
The eFlyer 2 will be followed in the manufacturer’s product lineup by the eFlyer 4, a four-seat, single-engine electric aircraft designed to complement the eFlyer 2 upward with greater range and greater payload.
Renowned flight schools such as KLM Flight Academy have already announced their intention to purchase aircraft from Bye Aerospace.
For example, KLM Flight Academy has placed orders for six eFlyer 2s and eight eFlyer 4s with Bye Aerospace.
Business Aircraft, Too…
But the manufacturer’s top model is expected to be the eFlyer 800, a twin-engine electric business aircraft with a range of 500 nautical miles and a service ceiling of 35,000 feet. For the batteries for this aircraft, Bye Aerospace is relying on lithium sulphur technology currently being developed by British company Oxis Energy.
They offer four times the energy density of the best lithium-ion batteries available today. Among the first customers to order the eFlyer 800 are fractional ownership companies Jet It and JetClub, Rheinland Air Service and air taxi company Air2E. The manufacturer says it has more than 700 firm orders for its electric aircraft family.
Hydrogen is seen by many as the aviation fuel of the future. Airbus and Embraer are looking to develop hydrogen-powered regional aircraft, while general aviation aircraft are already flying on fuel cells. On 25th September, 2020, a modified Piper PA-46 powered by a fuel cell from ZeroAvia took off for the first time in Cranfield, UK.
As early as 2022, the California-based start-up plans to offer its powertrain as an exchange engine, enabling its customers to fly emission-free. Hydrogen-powered aircraft do not yet have the range of conventional aircraft with internal combustion engines, but they do have a greater range than purely electric aircraft.
Even if leaded fuel were to become unavailable in the future, piston engine aircraft could continue to fly on alternative fuels for a long time to come.
Sustainably produced fuels from various raw materials that are not suitable for food production or power-to-liquid (PtL) fuels are solutions that will enable general aviation to fly sustainably and with low emissions.
Today, it is not yet clear which solution will prevail: all-electric, hybrid-electric, fuel cell propulsion, or internal combustion engines using sustainable fuels. It is likely that there will not be one solution, but rather different types of propulsion depending on the application.
Events like AERO in Friedrichshafen are the perfect spot to discuss the future of General Aviation and to explore new technologies on which manufacturers are working right now.