GENERAL AVIATION Flying electric aircraft
Ole Steen Hansen
Aerobatic display pilot, LAUREN WILSON gives a pilot’s perspective on the revolution in electric flight for general aviation.
The buzz of innovation in aviation is seeing much focus placed on electric flight. With electric cars becoming more and more mainstream and model aircraft and UAVs having been successfully battery-powered for years, it’s only logical that the industry looks to propelling people through the skies behind new, simple and silent electric motors.
The potential for ‘zero’ carbon emissions will make what must be one of the eco-warrior’s most hated hobbies much friendlier to the environment and the simplicity of pure electric drivetrains coupled with modern composite airframes should ultimately mean more efficient, faster and simpler aircraft. A bonus from this would also likely be a reduction in maintenance costs for owners and operators with simplified drivetrains. The ongoing operating costs of electric aircraft will not include reliance on expensive fossil fuels with their acquisition, transportation and storage costs.
A significantly lower airborne noise footprint, consisting solely of propeller tip noise, will yield less noise pollution and complaints around airfields. There are thus many environmental and operational advantages that make electric flight sound like the way of the future and it may well prove to be so in time. I’m just not sure that will be any time soon for the vast majority of us (I make an exception perhaps for gliding, with self-launching or ‘get me home’ electric powered engines in hyper-efficient airframes being one area of general aviation ripe for and advancing with electric expansion right now).
Back in May 2018 I joined a then very small group of pilots at the time to experience true electric flight, courtesy of Hungarian aircraft manufacturer Magnus. I was invited out to the factory to try out two of its aircraft, the Rotax-powered Fusion 212, and its Siemens Electric-powered brother the e-Fusion (left). Of course I jumped at the opportunity, as at that time there were only a tiny handful of fully electric aeroplanes to have actually flown and the e-Fusion was one of them. What’s more I was being offered the chance to try it out alongside (and in fact also flying it in formation with) a conventionally-powered version of the exact same airframe, which would provide the best possible view on what electric flight was really like, the comparison being direct and immediate.
THE TAKE-OFF ROLL FELT ALARMINGLY LONG AND THE CLIMB RATE HAD ME NERVOUSLY PEERING OUT OVER
THE COWLINGS FOR FEAR OF NOT CLEARING THE GENTLY ROLLING TERRAIN AROUND THE AIRFIELD.
What’s more, the opportunity was available to speak directly with one of the Siemens representatives and ask all manner of questions about the motor and battery system and how it was being developed – a truly fascinating discussion that ultimately left me with a great deal of confidence in the technology and enthusiasm for an electric future for general aviation.
Setting aside the spark of innovation, it is true that a cold, direct comparison of the aeroplanes I flew could easily have left me feeling deeply disappointed rather than ‘electrified’. The e-Fusion proved to be noticeably heavier than its Rotax-powered brother, being quite nose-heavy (with batteries) and feeling sort of sluggishly underpowered as a result. The take-off roll felt alarmingly long and the climb rate had me nervously peering out over the cowlings for fear of not clearing the gently rolling terrain around the airfield. The power demand had to be eased back fairly early on in the climb too, only exacerbating the wallowy, wafty feeling – using maximum/take-off power for too long would have left us with such limited endurance that I’d have had no opportunity to actually experience flying the thing, hence the early power back.
I have to say I spent far longer focusing on the power monitoring systems than probably anything else on the first flight. It was a little odd having an endurance measured in percentage – it was just like my mobile phone, except that, instead of counting down to an annoying loss of social media procrastination opportunities, it was telling me how long we potentially had before we became a very heavy and inefficient glider. This new level of stark situational awareness of the ‘fuel state’ split my opinion somewhat – on the one hand it’s great to be so obviously aware of the state of a flight-critical system, with no confusion or ability to be forgetful granted but, on the other, I couldn’t help but think about how often I’d seen my phone get down to 1% battery and thought ‘oh I’ll just send one more message’ and watched the screen go black mid-sentence… Knowledge of power is power isn’t it? Or is it just an opportunity to encourage complacency? Discipline will be a necessary trait of future ‘bright spark’ pilots for sure.
My next flights were far less fearful experiences, as I by then knew exactly what to expect and could enjoy this new novelty of the electric revolution. With endurance increased up to an hour or beyond, the whole experience will be quite different again and much more akin to conventional fuel management, so long as pilots and operators take the right approach.
The e-Fusion’s handling in the cruise was not wildly dissimilar to that of its conventional brother, although the difference in CoG with the weight of its batteries all in the nose was quite noticeable and definitely did not improve the handling. Everything felt less responsive, almost like trying to run in water. This didn’t come as a real surprise but is something that would need to be addressed in future – I suspect there could be a real tendency for a machine in this configuration to want to land on its nose and to also have some less than desirable characteristics at some of the edges of the envelope, aspects I’d wager are common to many new electric machines where piston powerplants have simply been replaced.
I do think that perhaps the future of electric flight will be in custom-designed airframes, as there are distinct limitations created by trying to fit a brand new square peg into a conventionally-fuelled round hole. We will definitely see advances in efficiency with airframes designed from the ground up around their new electric propulsion systems. New airframe designs could open up all manner of possibilities to get past some of the current space and weight limitations imposed when simply bolting an electric motor and battery ‘module’ in place of a combustion engine.
On the more negative side, it has to be said that one of my concerns with electric flight is fire. Around ten years ago I lost the entire contents of my house to a fire caused by a lithium battery that had been left on charge in the living room. This traumatic memory, coupled with my once-upon-a-time-back-in-the-day background as an electronic engineer, made sure that the majority of the questions I asked the Siemens representative during my visit to Magnus were around battery stability, thermal runaway and crashworthiness. When lithium burns, it burns hot and there is no stopping it, as Boeing discovered early on in the 787’s life when its battery APUs had a series of fire incidents on the ground.
NICHE APPLICATIONS, SUCH AS HIGH-SPEED ELECTRIC AIR RACING AND AEROBATICS ARE ALREADY
SEEING ELECTRIC AIRCRAFT BEING DEVELOPED AND HAVE A WHOLE AIR OF EXCITEMENT AROUND THEM
The thought of a thermal runaway leading to an inflight fire in a GA aeroplane is something that makes a cold shiver run down my spine. It’s fairly obvious that this is not a scenario any manufacturer wants and, as such, the stability of the battery chemistries used is just as important as the capacity they can provide. It’s no good building an aeroplane with several hours of endurance if mishandling can cause the batteries to catch fire after all. Despite my sensitivity, I have no doubt that the potential fire risk posed by lithium battery systems can and will be mitigated to within parameters no worse than carrying around tanks of highly flammable avgas. These systems by necessity run with incredibly advanced monitoring and regulating circuitry that provides phenomenal and pilot-proof safeguarding. The chances of a thermal runaway occurring in the flight I’d wager are actually far, far lower than the chances of an avgas fire in a piston aeroplane but the concept does need consideration.
Sadly, I need to mention that around a week after I had been to Hungary to fly the e-Fusion it crashed, killing the two on board and the batteries actually caught fire after impact, burning so hot I understand that little was left of the airframe afterward. Had it been a piston aircraft with full tanks of fuel the outcome would almost certainly have been the same but I do not feel there’s any argument to say an electric aeroplane provides any less of a fire risk in a crash and, in some situations, could have the potential to create additional challenges for responding fire crews. Crashworthiness and emergency responses are something that perhaps needs to be thought about with fresh eyes by those planning to operate electric fleets but this should not pose any real issues.
The flight training industry could find significant benefits in operating electric aircraft: noise, emission and ultimately cost reduction being areas I don’t think anyone could argue against. Manufacturers would need to focus on improving endurance to a point where sensible flight times could consistently and reliably enable lessons of over an hour at varying power demands (such as circuit sessions with multiple full-power climbs, or general handling sorties with stalling and practice forced landings also requiring multiple full-power climbs) plus a reserve, without the instructor needing to pay an inordinate amount of attention to remaining battery levels. The battery systems also need to retain this level of performance and not degrade too much over time and use – or at least be regularly replaced (and what will happen to old batteries? Will this be the new environmental issue for the age?).
I am not sure how practical electric aircraft would be for cross-country work until we start seeing flight times of two to three hours plus being possible. Infrastructure investment also being needed to enable recharging or battery changes at airfields away from home – not a problem for schools with planned agreements and airfield arrangements but what about the unplanned diversion or the student who gets lost on their solo cross-country and loses track of time? Of course, charging points would need to be standardised too between manufacturers – it would not be much use arriving at an airfield with a recharging point available but using the wrong connector or voltage.
These issues all apply for individual owners too, with the current high cost of airframes and the rapid rate of change likely to put off many potential buyers. Perhaps some kind of upgrade plans will start to become available, or leasing arrangements like those seen in the automotive industry?
There is a plethora of issues, none of which is insurmountable but will require a good deal of investment to resolve for electric aeroplanes to start becoming commonplace and will require some wholesale rethinking of exactly how pilots, instructors and students will be approaching the basics of flight planning and airmanship in electrified skies.
Niche applications, such as high-speed electric air racing and aerobatics are already seeing electric aircraft being developed and have a whole air of excitement around them that I am watching with great interest. Short duration sport flying is an ideal testing and development ground and the aerobatic world, in particular, could and will no doubt see all manner of amazing manoeuvres being developed that have previously not been possible. Electric air racing could be truly fantastic and, without the requirement for maximising endurance, we could see all manner of speed records set and broken and fantastic spectator sports being born.
The advantages of designing an airframe around a new powerplant technology will undoubtedly start to be seen most clearly in these experimental arenas too and the advances made will no doubt ultimately trickle down into the industry proper.
Electric dreams
Left: Pipistrel achieved EASA certification for its all electric Velis Electro. Right: Rolls-Royce is aiming to beat the electric aircraft speed record with its ACCEL racer. Pipistrel
I do think electric flight has a very bright future. Technology continues to advance at a rapid pace and with such a huge focus on the development of electric cars right now we will see more and more elements that can and will transfer across into aviation. Right now electric flight is in its infancy and limited by its battery technology, with flight endurance currently being too poor in most cases for much beyond short local flights. Perhaps sightseeing or early circuit training could make good current use cases for electric aeroplanes with their lower noise profiles. Quickly – changeable battery packs will potentially enable longer flights with hops between airfields with charge or battery stations. The infrastructure will, of course, require investment and standardisation, just like the networks of electric car-charging points that are now becoming commonplace. Whether the general aviation industry will stomach this kind of investment in what will be a very niche market over the next few years, I’m not too sure but time will no doubt tell.
What though of the hybrids? Electric aeroplanes without the limitations imposed by pure battery power? This is another topic entirely and I can’t help but feel hybrid-electric flight may be the area to watch for general aviation, as well as the commercial sector. Systems with longer endurance and better redundancy than pure electric systems but having the advantages brought by simple electric drivetrains; simple automated systems, lower emissions, lower operating costs and quieter aircraft – perhaps the hybrid world may be the next major stepping stone. I guess I need to fly a hybrid aircraft next.
Light Aircraft Design Conference 2020 – Electrifying General Aviation II 16 November 2020