As I learn to fly, piloting 1960s leaded-gas-guzzling light aircraft around the incredible green scenery of Northumberland in North-East England, I sometimes feel guilty about contributing to the carbon emissions into the atmosphere. I say sometimes only because flying is so absorbing, the post-lesson guilt is real.
So I’ve been looking into what other options exist for sustainable general aviation (GA) and aviation more broadly. I’ve been pleasantly surprised to find leaps in technology that will help curb some of the emissions from commercial flying, and shocked to find we’re closer to a carbon-free GA future than we might imagine.
The 2nd-order effects of electric GA options could transform how we travel.
State of the Nation: Sustainable Aviation
In the world of airliners, the area of most intense research and development is in fuel. Biofuels and synthetic fuels are being tested including on passenger flights.
A leader in this space is Gevo, who recently signed a 5 year deal with OneWorld airline alliance members (including British Airways, Qatar Airways, American Airlines, and many others) to provide 5 million gallons of sustainable aviation fuel (SAF). Gevo’s SAF is called, big breath, Alcohol-to-Jet Synthetic Paraffinic Kerosene, or ATJ-SPK for short(ish).
Gevo’s fuel meets and exceeds the stringent ASTM D7566-22 standard for aviation fuel, meaning it is ready for immediate deployment into the global fleet of commercial aircraft.
Current battery technology doesn’t offer the same energy density as kerosene, so all-electric airliners are not yet possible. Airbus have been experimenting with hybrid fuel/electric aircraft since 2009 with their largest electric-hybrid aircraft to date intended to be the E-Fan X project.
In partnership with Rolls Royce and Siemens, the E-Fan X aircraft would replace one engine from a 4-engined British Aerospace 146 regional jet with an electric motor. However, the project was scrapped during the COVID-19 pandemic.
But all is not lost and Airbus are continuing to look at hybrid aircraft for the future. It’s conceivable we will see aircraft with more than one type of engine in the future – SAF-burning internal-combustion engines for maximum and sustained power delivery and electric-powered engines to supplement cruise phases of flight and low-energy phases such as descent and taxi.
Near-zero-carbon commercial passenger aviation is close, if we can begin mass-producing SAF, but if we do then the carbon footprint of aviation will come down dramatically.
Is Zero-Carbon General Aviation Possible?
General Aviation (GA) has different operating constraints from the airlines. A quick definition first:
GA is defined as any civil aviation operations that aren’t commercial passenger transport or “aerial work”, which includes things like crop spraying and aerial photography. GA includes business flying and training.International Civil Aviation Organisation (ICAO)
While GA includes business jets (biz jets), these typically have the same challenges as airliners – larger aircraft and long-range routes – so I’ll discount those from this section and instead focus on light, propeller-driven aircraft.
Your typical GA aircraft is a Cessna 172 or a Piper Arrow, a single-engined, propeller-powered, Avgas-fuelled plane.
The Cessna 172 is the most-produced aircraft in the world with over 44,000* built since production started in 1956 (* per Flight International, June 20, 2017, p. 24.) so this is a reasonable place to start thinking about how we could electrify this type of aircraft.
Slovenian aircraft manufacturer, Pipistrel, is leading the push for electrifying GA. They currently have two electric aircraft on sale, the Taurus Electro, which is a touring motor-glider (TMG), and the Velis Electro, a light-sport-aircraft (LSA) category training aircraft.
Aviation vlogger Stefan Drury took it for a spin in Australia:
A few things stand out, it’s an impressive machine but let’s first address the elephant in the room: the range.
The Pipistrel Velis Electro (originally called the Alpha Electro as you’ll hear in the video above) only has 50 minutes of endurance. This is a problem. Even for the most basic of lessons you’re going to need at least an hour of power – including taxiing and travelling to the training area.
Charging time is good though, with 50 minutes of flight time only requiring 60-75 minutes of charging. This is still not good for flight schools which often have lessons back-to-back for the whole day. You’d really need two electric aircraft where previously you’d need one.
But the Velis Electro is quick, has a good useful payload (172kg) and is very very quiet. I’ve mentioned before that one of the main challenges in general aviation is avoidance of rich people’s houses (noise abatement), so this will help the often-fractious relationship between local communities and their nearby airfields.
Light Sport Aircraft are those with a maximum take off weight (MTOW) of no more than 600kg, but the Cessna 172 and similar are Category A light aircraft and the 172 has a MTOW of over 1,100kg. UK pilots can even fly aircraft up to 2,000kg on a Light Aircraft Pilot License (LAPL, previously the National Private Pilot’s License or NPPL) which has much lower requirements than the internationally-recognised Private Pilot’s License (PPL). This leaves plenty of room to grow the Velis LSA concept into something Category A sized and with more batteries – improving range and endurance to a point where it can truly compete with the sexagenarian training aircraft people like me currently learn in.
I was also a little unfair mentioning the taxi time as you can turn off the electric motor when you’re not using it, whereas in an internal-combustion engine you don’t really want to keep turning it on and off as you taxi and hold. Your taxi time will be reduced with an electric aircraft too as you don’t need to do things like checking magnetos – although there will (I suspect) be some kind of power checks before take off.
A common complaint about electric vehicles is the source of the electricity. It’s not very environmentally friendly if your Tesla, Taycan or Taurus Electro is being charged by a coal-fuelled power station, but this is where I think we’re going to see the GA landscape really change.
Key Infrastructure Changes Required
One thing that most GA airfields aren’t short of is space.
It’s not unreasonable to envisage hangar roofs and unused areas of the airfield have solar panels installed. This would not only be used to charge the aircraft but would also reduce the on-grid power consumption of the airfield itself.
There is also the problem of charging, although this is now seeing positive movements. Using Pipistrel equipment, Old Buckenham is one of the first airfields in the UK to have electric aircraft charging stands available:
Solar panels are quite costly, though, and we do need to see better economics around these, their installation, up-keep and ultimate disposal. However, there are serious cost benefits to electric aircraft that I think are being overlooked.
The Total Cost Benefits of Electric GA Aircraft
Internal combustion engines are really complicated. They need oil, inducted air, cooling, plumbing for fuel, dual-ignition systems, and exhausts. There’s also alternators, turbochargers for improved induction at altitude, and dampening for vibrations. Electric aircraft need none of these (except simple cooling perhaps).
The engine is the source of a lot of the cost of owning and operating an aircraft. Oil needs regularly changed, oil pressure and temperature need to be constantly monitored while flying, alternators and pistons etc are expensive to replace too.
Electric aircraft are much more simple, with only one moving part in the engine. If classic steam gauges are replaced with electric then there’s no need for a vacuum system either (this is true for conventional GA aircraft). And this is where I think the real cost benefits lie.
Much lower maintenance costs, fewer things to go wrong, less to check during regular servicing and fuel supplied from renewable sources. These add up to serious savings and even makes the scenario where a flight school needs to buy 2 electric aircraft where one ICE powered aircraft would have done before a more reasonable scenario.
|Conventional GA aircraft||Electric GA aircraft|
|Fuel||+ Can be quickly refuelled.|
+ Fuel has high energy density meaning good endurance
– Extremely flammable fuel usually carried in wing tanks.
– Requires fuel pipes to carry fuel to the engine.
– Low-wing aircraft may need fuel pumps.
– Oil has a high cost and will run out at some point.
|+ Electricity can be sourced from renewables.|
– Batteries do not offer as much energy density as kerosene-based fuels
– Batteries have questionable supply-chain environmental impacts
– Takes a long time to recharge
|Lubrication||– Required regular changes of aviation-grade oil. |
– Oil needs to be checked before each flight.
– Oil temperatures and pressures require continual monitoring during flight.
|+ Minor / Not required|
|Cooling||– Typically air cooled but requires radiators||+ Simple passive cooling of the motor and batteries would suffice.|
|Forced induction||– Heavy turbochargers used in some aircraft for better performance at altitude||+ Not required.|
|Mixture||– Fuel/air mixture needs to be adjusted at different air densities|
– Incorrect mixture can lead to engine failure
|+ Not required|
|Ignition||– Dual ignition systems provided by heavy (but reliable) magnetos|
– Spark plugs are a common point of failure (e.g. carbonisation, wear)
|+ Not required|
|Vibration||– Requires damped engine mounts||+ Not required|
|Checks and Servicing||– Requires regular engine checks|
– Requires periodic full-engine-overhauls
|+ One moving part|
+ Motor is self-contained with minimal plumbing – simple to replace
+ Far fewer failure modes
Thinking Further Ahead and Investment Opportunities
The future of aviation looks very different from today.
Airliners have hybrid fuel/electric power, and may even have multiple sets of engines for different parts of the flight.
Aviation fuel is synthetic and/or made from biofuel, releasing only the carbon absorbed during the growth of the cereals back into the atmosphere.
All-electric general aviation GA aircraft are everywhere, airfields use solar and wind power to charge the aircraft (and power the airfield itself). Continual improvements in solar panel technology and batteries means aircraft range and endurance only gets better with time.
General aviation safety levels improve as aircraft are simpler and there are fewer points of failure. Servicing is also simpler, with only one moving part to check. Lower costs mean more people can afford to own their own light aircraft.
But then what?
Electric aircraft becoming cheaper doesn’t automatically mean more people own an aircraft, the opposite might be true. As we see with cars, private ownership of vehicles in large cities has fallen and on-demand taxi services like Uber has exploded. Electrified aircraft can be designed to be vertical-takeoff-and-landing (VTOL), and with good auto pilot capabilities and geo-positioning technologies, could become the airborne backbone of travel beyond local A-to-B trips.
This isn’t radical, Uber already introduced Elevate, a point to point air taxi service, which was bought by Joby Aviation in 2020.
Uber cars are ubiquitous in major cities, but major cities are a major pain to traverse by car. Adding a third dimension to urban transport networks is a scalable solution. Ultimately, this is the reasoning behind Elon Musk’s tunnel-based transport company, The Boring Company, but without the cost of drilling huge tunnels underground.
As ever, the way to make money from this transformation is by investing in the picks and shovels. This future requires more batteries, more solar panels, lightweight and strong composite materials and chips for ultra-precise autopilots. If this future becomes a reality, which I think it will, investing in these supply chain technologies are likely to have great returns.