Electric C172 first test flight

[Shiny Side Up]

I can see how an electric aircraft might be an attractive choice for recreational flight training, but for aspiring commercial pilots, it is certainly a no-no.

The recreational/PPL type market is a large one though so in terms of having a couple of these machines on the line at a FTU it certainly would be a revenue generator. There is no reason either why all PPL training couldn't be done on these aircraft, even for aspiring commercial pilots. I could see a license restriction though for those who did all their training on such an aircraft. If one could reduce even sligthly some of the costs of RPP and PPL training though I would be certain one could significantly increase one's market share in a particular area - especially if one was the first to put such machines on the line. Easier and cheaper to fly is a big seller - as I said before, merely the idea of a six-bladed prop would simply draw a lot of interest from a lot of the GA community.

I'm not a big fan of Diamond aircraft but with that basic design they could make a good electric trainer

I doubt that the diamond would work as well as the Cessna, if only because it leaves a lot less room for modification. A conversion of this nature would pretty much mean a ground up redesign. Part of the reason a 172 makes such a good candidate for this project is the ample room and very generous CoG limits. As it is right now, you could put two people in a 172 and 700 extra pounds and it would be within its limits. One wonders if an electric 172 will still be certified for spins...

Either way, it will be interesting to see.

[iflyforpie]

One problem will be the recharge time. You will have to have two hour breaks between flights, which will mean lower aircraft utilization and higher fixed costs. Also, can you imagine doing a cross country and having to wait to hours to fill up? What if there is more aircraft than receptacles at the electron replenishment station?

I would imagine in time that these issues might be ironed out. Another thing I am wondering is if solar cells could be used as range extenders?

[CpnCrunch]

The Yuneec's battery pack costs $20k and lasts 2000-3000 hours, so that's $10/hr which is on a par with your typical 172 gasoline engine.

http://www.wired.com/autopia/2010/10/el ... -near-you/

It also has a swappable battery, meaning you can fly all day (in theory).

The diesel/electric hybrid 172 sounds interesting, although I'm wondering how much it would weigh.

[Posthumane]

I think the Yuneec will make a better training aircraft in the near future than the C172 concept. It's a much less draggy design, and has been flying for some time now. Yuneec has a fair bit of experience in the electric market and have real world numbers to back up their claims.

When my friend and I started thinking about our project we had hoped to be the first in Canada marketing an electric conversion, but it's quite likely that someone will beat us to it. Either way, I think electric airplanes have the potential to give the GA industry a big boost.

[hawker driver]

One problem will be the recharge time. You will have to have two hour breaks between flights, which will mean lower aircraft utilization and higher fixed costs. Also, can you imagine doing a cross country and having to wait to hours to fill up? What if there is more aircraft than receptacles at the electron replenishment station?

I would imagine in time that these issues might be ironed out. Another thing I am wondering is if solar cells could be used as range extenders?

Extension cords for the circuit.

[. ._]

Interesting to see how much charge they hold during winter as well...

That's what I was thinking. An electric defroster at -20 would really suck some juice.

But wouldn't it be cool to go for the $100 hamburger and it only costs you $10 in hydro?

[Heliian]

so, how much will it cost per re-charge. the current rate is about 10cents/kwh at home, it'll be way higher by the time electric a/c designs get off the ground. How many kwh's would it take per charge?

[Posthumane]

Lithium polymer batteries have a very high charge/discharge efficiency (over 99% quoted) so you can get about as much energy out of them as you put into them. Chargers are not 100% efficient though, closer to 85% for the good ones. So for a 30 kWh pack, you would need to provide about 36 kWh of electricity, or about $3.60 at 10c/kWh.

Looking at Kokam's high power cells, looks like they are getting close to 140Wh/kg, so the C172s could have up to 43kWh installed at their given pack weight, if they managed to keep the connectors and battery management system light, so the charging cost would be just over $5, which is what they claim in the article.

Cold weather does obviously affect any batteries negatively, and this is a big consideration for aircraft flying in Canada. The batteries would have to be insulated well, and have some amount of active heating as well like in some electric cars. It might be practical to scavenge some of the waste heat from the motor to heat the batteries in the winter while it's running.

Heating and defrosting the cabin is actually not that big of a concern as it might seem. Large electric motors do give off a fair bit of hear and have to be cooled (excess heat will kill a permanent magnet motor). Brushless motors can be over 95% efficient, but even 5% of 30kW at cruise power is 1500W of heat. Controllers have a fair amount of heat loss from some inefficiency as well.

Gas motors are obviously a lot less efficient (about 30%) but most of the excess heat escapes with the exhaust gasses.

[. ._]

Heating and defrosting the cabin is actually not that big of a concern as it might seem. Large electric motors do give off a fair bit of hear and have to be cooled (excess heat will kill a permanent magnet motor). Brushless motors can be over 95% efficient, but even 5% of 30kW at cruise power is 1500W of heat. Controllers have a fair amount of heat loss from some inefficiency as well.

Oh yeah! I forgot about that!

Can you tell I'm not an engimineer?

[seniorpumpkin]

I was wondering if anyone would notice or care that this was happening.
It's been a dream of mine for years, and I think the business model really works. $50g for a conversion, gives you a trainer that is the same airframe as the internal combustion version, but costs a small fraction to run- its a no brainer. Any FTU could use the electric plane to teach basic attitudes, turns, circuits, all that. It would be easier to fly, starting would be a matter of flicking a switch. The cessna line is perfect because all planes are inherently designed to be light and efficient and cessnas are super prolific. A cherokee might also be a good choice.
The disadvantages are easily mitigated if you ask me.
Posthumane, if you want to get together, write out the business plan, and go find some funding I'm all for it! I can see partnering with Bye energy and Cessna. Lets let them do all the hard work of figuring out the engineering, then we can take their design, certify it with TC and start selling conversions!

[Posthumane]

Seniorpumpkin - I agree with you that this is the time to go for it, and echo your enthusiasm. There are some disadvantages, but for flight training and recreational flying they are indeed easily mitigated. However, I disagree about the Cessna or Piper line being a good choice for a conversion. They are neither light, nor efficient, compared to contemporary designs. Even as a two seater, I doubt that the C172 can be made under 1600-1700 lbs empty. There are many LSA style designs which could be converted that have a much higher L/D (i.e. less drag), and less weight. The Long-EZ was our top choice due to its efficiency and speed, though we may go with a larger wing/slower aircraft to reduce pack size (power required is proportional to airspeed and drag).

As far as a business plan goes, my business partner and I already have one of those drawn up (though, admittedly, it could use a bit more work) which we have used to approach potential sponsors. A partnership with someone like Bye is a possibility, but we initially shyed away from those kinds of partnership due to a possibility of losing control of the project. We wanted to keep it fairly "open source" so to speak, and promote electric flight as much as sell a product. Once I get our old webpage ported from my little home server to a proper one I'll post a link to it here. If you'd like to be involved, we could certainly be in touch.

[seniorpumpkin]

Fair enough, I just think the business potential of converting Cessnas may be a better option. The technical side would be more challenging. As long as we could get the weight under 1900 or even 2000 lbs, you've got a usable trainer.
Simply promoting electric flight is certainly a noble enough reason to embark upon this path though.
Instead of hijacking this thread any more than we already have, check your pm's
Also if anyone out there has a bunch of money, or has some potential leads for sponsors... you know what to do.

[CpnCrunch]

Guys, the $.10/kwh figure is way out. Looking at my current ATCO Electric bill, the current variable charges last month were $0.27/kwhr. I think the $0.10 figure is either from the USA, or maybe that's the wholesale market rate of the electricity that comes out of the generating station (in Alberta that's currently $0.05-$0.07/kwhr, and the cost of distribution and transmission is about $0.20/kwhr). Then add the profit margin for the FBO, and you've pushed the price they'll charge you to charge your plane up to about $0.45/kwhr.

The only possible way it would cost less is if the FBO got a discount for higher usage (my last electric bill is based on 250kwhr/month).

I still think electric planes are a great idea though - if they can sort out the weight/cost/range issues.

[Posthumane]

Ha! That's what you get for living out in the boonies (or the badlands). Looking at my electricity bill from the city of Medicine Hat, my overall rate sits around $0.10/kWh (.0698 energy charge, .0071 admin charge, .0115 facilities usage, .0016 system access fee), plus a few dollars monthly service charge that is not prorated per kWh. It varies a bit of course, but I've always used $0.10 to $0.15 for all my cost estimates.

Seniorpumpkin - yes you would have a usable trainer if it weighed 1900 lbs, but the power required to keep a 1900 lb airplane in the sky is significantly higher than required to keep a 1200 lb airplane up. More power = more batteries or shorter range. If you start off with an airframe that has a much lower empty weight without the engine (Long EZ airframe can be built to be just over 500lbs) and install 700lbs of batteries and motor, you could have a very usable package.

[Shiny Side Up]

Cold weather does obviously affect any batteries negatively, and this is a big consideration for aircraft flying in Canada. The batteries would have to be insulated well, and have some amount of active heating as well like in some electric cars. It might be practical to scavenge some of the waste heat from the motor to heat the batteries in the winter while it's running.

This got me thinking a lot. The solution I believe kills two birds with one stone. Go to any big box store - you'll find the upright type close-quarters forklifts in use, these machines are all electrically powered - they have the advantage of course of using the weight of the battery as a counterweight as well. The main feature one will note is that the battery is removable. Having worked on these machines in the past, a battery swap can be accomplished in a matter of minutes. Any usable aircraft that is electrically powered is going to need this feature. Two airplanes immediately come to mind - a Cessna U206 and a Cessna 180/185. A 206 of course has a large door to make it easy to load in large heavy items - it would be easy enough to take all the seats out and modify the rear area to pack battery weight (of course then you also need an electric motor to crank out around 300 horse up front...) Constructing a cart to roll-out, roll in batteries with would be simple enough. 185/180s on the other hand can be equipped with a belly pod already, the tail dragger config giving lots of room underneath. A pod could be constructed to hold batteries once again which could also be easy enough to make to swap out, probably by way of a device similar to a bomb cradle - easy enough once again to construct if you're reasonably mechanically inclined.

Keep in mind all we're really after here is proof of concept. Both of these airframes can heft the 700lbs+ of batteries we're talking about needing, one might also consider - being cheap on a prototype seeing how many lead-acid type batteries one could heft into the air...

Either way, a quick change type system is going to be needed for quick turn around on the machines, essentially like the forklifts, so you always got batteries on the charger. Secondly this also means the batteries get removed from the airplanes when they're not working and stored somewhere warm when not in use....

[North Shore]

Guys, the $.10/kwh figure is way out. Looking at my current ATCO Electric bill, the current variable charges last month were $0.27/kwhr. I think the $0.10 figure is either from the USA, or maybe that's the wholesale market rate of the electricity that comes out of the generating station (in Alberta that's currently $0.05-$0.07/kwhr, and the cost of distribution and transmission is about $0.20/kwhr). Then add the profit margin for the FBO, and you've pushed the price they'll charge you to charge your plane up to about $0.45/kwhr.

The only possible way it would cost less is if the FBO got a discount for higher usage (my last electric bill is based on 250kwhr/month).

I still think electric planes are a great idea though - if they can sort out the weight/cost/range issues.

So what if the $.10/kwh is out? The quote was ~$3.60 for a charge on a 30kwh li-po battery. Even if it goes up to $.50/kwh, then our charge only goes up to $18.00 - still cheaper than gas..

As for the weight/range/cost issues, we North Americans have got to start getting used to the idea that the era of cheap energy is drawing to a close - that it is 'normal' in the range of human experience to be able to travel in our vehicles at 50mph for 500 miles or so for a cost of a tank of gas ~ $55. Aviation will be no exception to that rule.

[pilotidentity]

I like the idea of the sun recharging the batteries. How many 172 sit around only being used once in awhile? Nice to go out to the airport for your weekly flying fix and have the "tanks" magically be full all the time.

[Posthumane]

I don't think a high power, high weight capacity airplane is the way to go for a proof of concept. If you need to be putting out 150+hp in cruise then you are going to need a lot more batteries, which offsets the additional payload of something like a C180. Essentially you get the same 2 person plane, but one that weighs more, uses more power/energy, and costs more to build (the batteries at this point are the most expensive item).

Being able to swap out the batteries quickly is a must, I have to agree with that. LiPo batteries have a pretty high volumetric density so the 600lbs (or so) of batteries that you would need would take up less room than the 40 gal of fuel it is replacing. In other words, space is not really a huge issue. You could, for example, have the pack divided up into 12 x 50lb packs, each consisting of 25 40Ah cells. The dimensions of each pack would be about 22cm x 22cm x 25cm.

Pilotidentity - if you are just looking for the convenience of leaving your plane for a few days and coming back to find it charged, I think plugging it into mains power and leaving it would be much more cost effective than solar panels. It may not be as "environmentally friendly" but is a lot cheaper and then you don't have to lug around the weight of the solar panels. Even thin film cells weigh a noticeable amount.

Anyway, I'm slowly moving stuff from my old home server (which died recently) to http://panlogieaviation.ca but it will probably take me a while since I'm tied up with some other things at the moment. My apologies about the appearance of the page at the moment and the lack of content, but it will come with time.