Many pilots are concerned about the fire issues associated with lithium polymer batteries, and it's true that they are highly flammable and explosive, very much like gasoline. The batteries are safe, however, as long as they are not overcharged, something that the onboard charging and power conditioning system would ensure. LiPo batteries react with nitrogen, a plentiful atmospheric gas, and with water. So in a crash, a compromised battery housing could lead to fire. The same is true, again, for gasoline, when it is exposed to a source of ignition.
In addition to the motor and the batteries, the power system on Bye's Skyhawk will need a power conditioner and new controls and engine (motor) monitoring displays. Bye won't say with whom he's working to develop the displays, but it's not hard to imagine that the Garmin G1000 in new Skyhawks could be modified to work nicely for power monitoring.
Upsides One of the big benefits of the system will be its low noise. It's likely, in fact, that the airplanes will require a horn so that pilots can alert people on the ground of an electric Skyhawk's approach. The neighbor-relations benefits to flight schools, especially busy ones in noise-sensitive areas, would be great. Pilots too would reap the rewards of flying in a very low-noise cockpit.
Other benefits have to do with the characteristics of electric motors compared with gas-piston ones. Starting is automatic. Mixture control is a no-brainer, because there is no mixture. There's single-lever power control — a quick glance will tell you what the power setting is and how much more flying time you have.
Electric motors also don't run on oxygen, so they will be efficient at high altitudes and density altitude won't be as big an issue — wings, however, will still rely on the density of air to do their thing. While it's not a major perk for training, an electric motor's indifference to air means that it would be a great high-altitude power plant, with all of the upsides of a turbocharged gas-piston engine without the increased fuel consumption or overheating concerns.
With growing concern over the cost of training, the allure of electrics is very strong. Just think of it. Go flying for an hour, get back, plug in, pay a few bucks for that electricity versus around $40 for avgas (eight gallons for an hour's flight at $5 per gallon) and head back up again, literally for pennies on the dollar.
There are additional savings to be had. The costs of gas-piston engine maintenance and overhaul are very high, but electric motors need much less maintenance and their TBOs are nearly unlimited. For the short term, cost of operation of an electric Skyhawk will be much, much less than for a conventional one.
But airplane owners aren't in it for the short term. And long term, there are big questions about electrics. First, battery cost and battery life (two closely related subjects) are hard to predict, and Bye Energy isn't going out on a limb here. How long will the batteries last? And how much will it cost to replace them? Both are unknowns at this point, but suffice it to say, the cost will be high and the time between replacement (TBR) will not be long enough to make owners as happy as they would like to be.
At this juncture, it's likely that electric Skyhawk owners will be spending a great deal more on battery replacement than they would have spent on engine overhaul, probably in the neighborhood of three times as much. But then again, the savings in fuel and routine maintenance will balance that out to a great degree.
Until the details are known, however, it's impossible to say just how much more or less it will cost to operate an electric Skyhawk compared with a conventional one. But one thing is sure. As battery technology improves and prices come down, which will very likely happen over the next few years, the economics of electrics will begin to outweigh the airplanes' limitations, which for now require a return to home base within a few hours.
One potential option is hybrid power, which Bye Energy refers to as APU use. In this case a small generator engine (powered by jet-A, says Bye) would provide additional power to charge the batteries. This solution, however, would require the installation, care and feeding of two separate power systems, and it would require carrying an additional fuel source and additional weight, all of which undermine some of the gains that electrics promise going in.
Still, the promise of electric power is great. It seems to be dependent on the development of better batteries. Today's batteries are, in fact, much improved over those available commercially just a few years ago. And they do seem to be good enough now to make everyday electric flight, if not an economic godsend, at least a realistic alternative in some segments of the industry to the gas-piston paradigm.