The Electric Revolution Begins

If you were at AirVenture last week you probably at least heard people talking about electric-poweredairplanes. There were at least three of them there at the show, and one, the Yuneec e 430 is actually a commercial product. You can reserve one today for around $90,000, and Yuneec expects to be delivering them soon.

Is it a viable product, though? Well, it actually sounds as though it's close to that. With a big battery pack, the airplane can fly for up to three hours, and there's plenty of available payload. (Strangely, with this airplane, there's no fuel weight; the batteries are part of the airframe and electrons, last time I checked, didn't weigh much.) So, you can get two good-sized guys in there and go flying for three hours. With the equivalent of 54 hp, you won't go very fast, 60 knots or so, and you won't go very far. And because you're battery powered, you'd better be landing somewhere you can stay for a three or four hours, if you can find a place to plug in, that is.

Flight schools have already begun to express interest, and with "fuel" costs of around $2.50 an hour, compared with roughly 7 or 8 gallons per hour at $4.00 a gallon, that cost is very low. Sure, the batteries cost a lot, as much as a small used car, but the engine overhaul and maintenance costs are pennies on the dollar. And a flight school could always have spare battery packs charging waiting to be popped into an airplane that was "out of fuel." That model makes excellent sense. Cross country flight is another matter.

But even that is likely to change soon. The most promising idea is hybrid power, with a small (or not so small) gas or diesel engine powering the airplane when the charge runs low, or for climb, and charging the batteries up in the process. Fifteen or 20 hour endurance figures are not out of the question.

Until we see significant advances in battery storage capacity, which is almost a certainty, the electric technology we see today is an interim step. Promising, but not good or affordable enough for mainstream users to adopt. And electrics probably have their limits. Without some unimaginable breakthrough, an electric-powered King Air remains the stuff of science fiction.

Comments

[Mike]

Electric Hybrid is the future of flight. If we can't bring the cost of the aircraft down we have to bring the operating costs down.

[Alan Gilmore]

Electric hybrids are good for stop and go traffic. This works great for cars that stop at traffic lights because it charges while running so there is not any wasted energy at the traffic light. An airplane on the other hand does not stop. At best it operates over a range of speed, but mostly at cruise.

Think about this...how does the mileage of a hybrid car compare to the mileage of a conventional car. It is much better in city traffic, but it is only comparable while on the highway. In reality a hybrid car gives you "highway mileage" while in "stop and go traffic".

So...IMHO...a hybrid electric does not solve many aviation problems, but does add cost and weight, two things that GA hates.

A pure electric airplane does make some sense. Recharging time and run time are two of the main problems, but there are some places in aviation where this is not as much of an issue. One of the key areas I see this working is in the motorized soaring applications. Short run times are used to climb, then long off times are used for soaring. Little energy is used since most of the energy comes from the thermals, so small batteries would be used. Optionally, larger batteries could be used so that a full days worth of climbing/soaring could be done, then charged overnight.

Fortunately, brushless motors and lithium batteries are here to stay, and they will probably find suitable applications in aviation. But these applications will be very specific and not universal.

[Robert Goyer]

Weight is an issue with hybrids, but they answer the one big can of worms with electrics, recharging issues. I'll bet that intriguing hybrid solutions come to the fore within the next couple of years on very light airplanes.

[Ed Dolejsi]

Some thoughts on electrics;

I agree with the comment that electric planes could be attractive to flight schools, but only the operating cost is considered. Flying electrics and flying conventional planes is very different. The two propulsion sources require very different management. A pilot trained on electrics only, would be completely oblivious to the attention required to operate a conventional aircraft engine. A combining electric and conventional power training would have to be the norm.

For a private use the electrics are not economical at all. The cost of batteries is extremely high, and while the recharging is inexpensive, and they could be good for 1000+ recharge cycles, which represent some 1500 flight hours, they have a definite shelf life. Over the years I discovered that my LiPo batteries are good for about two years, regardless if I use them or not. Maybe that is why the Toyota Prius is using conventional lead acid batteries.

The bottom line: if you fly 50 hours per year, and the battery pack costs $10,000, and it is safe to use for two years, then your “fuel” cost per hour is $100. At $4 per gallon you’d be burning 25 gallons per hour. Even if you include the cost of engine maintenance, flying marginal two-seat electrics at 60kts, instead of a very fast four-seat single, doesn’t seem to make much sense.

Someone said it already. Today’s electrics are an interim step, so a very big thanks must go to the e-enthusiasts, and the early adopters out there, because without them we would never have an electric flight.

Sincerely,

Ed

[Ludwik]

Hybrids are not a bad idea as posted above. The avgas or diesel engine that would be use would only run part of the time and when it does run it will run at its most fuel efficient setting. It will add mass but it might be possible to use a smaller engine to power the same aircraft.

[Miles Kimball]

Hybrids show great promise - particularly pure hybrids, where the combustion engine is separate from the power train and simply runs a generator to charge the batteries. It would take only a very small, fuel-efficient engine to do that - 10 horsepower or so? To get a picture of how small and light this could be, imagine using some of the Yuneec's payload to carry a portable generator like those used on construction sites. A small Honda generator (3000 watts) weighs about 70 pounds - surely an aviation-grade installation could be done for more like 50. It burns about 0.5 gph, so there wouldn't be much fuel to carry, either.

As Ed points out, battery cost is a big hurdle for economical use - but there's a lot of work going on in that area, and aviation can benefit from the economies of scale provided by automotive R&D.

[Frank D. Szachta, Major USAF (ret), Major CAP, ATP, CFII, SE & ME Land]

Asanelderly pilot (solo in a J-3 in 1946), and a Bomber (B-47) pilot during the "Cold" war, and a transport pilot for several years, and a GA pilot since (Mooney and Cessna 172/182 with Civil Air Patrol, I feel the e-Plane (batteries) could be a great Search and Rescue (SAR) plane for the CAP. The G-1000 C-182 is too complex for the mission (VFR SAR) and the slower speed would be a boon for the CAP.

Soaring also would be a likely use of this slower pland.

[Robert Goyer]

There's also talk of adding solar panels to the wings to charge the batteries in flight and add endurance. The high cost of batteries is a certain issue. Whereas a piston engine can last decades with regular maintenance, even if battery life is 5 years, which might be a stretch, the cost of replacement is very high. Then again, you're not doing many of the routine maintenance jobs on your motor you'd otherwise be doing on a piston engine. There's no oil to buy, and no oil changes, there are likely to be substantially lower annual inspection costs, and the engine overhaul costs are out of the equation too. These airplanes, as one poster suggested, are certain to be better utilized when they're flown a lot. Whether that's feasible at this point remains to be seen.

[Own Three Hybrids]

Had the dreaded IMA (Integrated Motor Assist) light on my Honda Insight. Original estimate was $5530 for not only the battery but two controller modules. Package deal, hey? Luckily Honda had already voluntarily extended all the original Insight warranties to 150,000 miles and 10 years (from 80,000 and 8 years). Correct Mr. Goyer, there's nothing much a user can do to save the battery like one can with loving care of a gas engine.

True too, the hybrid system has MOST effect for stop and go situations. Coasting/braking recharges the battery using the Motor-Generator: acceleration uses this energy to assist the gas engine. On the open road, the fuel efficiency is mostly from drag and friction reduction. However, descending and climbing hills utilizes the hybrid M-G charge and assist. The same M-G could work similarly in an airplane. When idling and gliding power-off, the motor is now a generator recharging the battery.