SR22 Electric Conversion

Guest Discussion
#1

Hi all,

I’m part of an enthusiast team that’s building an electric conversion kit for a SR22, and I have a quick novice question for you. I’m looking for a needle in a haystack.

Do you know anyone who fits this mission profile:

  • Flies at least 2x per week
  • Route is < 200 km each way
  • One or two people on board, with minimum cargo
    I’m looking for this person because we want to build this first plane with a pilot who already flies a route that’s similar to what our plane can handle. Our first plane will have a pretty short range because of battery limitations, and there isn’t much cargo space because of all the batteries we’ll need.

The tradeoff is a 30% drop in fuel costs, 3x reduction in cockpit noise, and obviously zero emissions, in exchange for reduced range and payload. I’m trying to find someone for whom that tradeoff is a “good deal,” which means they probably don’t fly very far or with much cargo.

Thanks a lot in advance!

#2

You won’t have much trouble finding people flying twice a week, alone or with one passenger, but the range is going to be a killer.

Your 200 KM, or about 110 Nautical Miles is pretty short; it’s a trip from New York City to Philadelphia in a plane built to go from New York City to Chicago. (By the way, at SR22 speed, 110 NM is only about 40 minutes, and you need at least another 30 minutes on top of that for the smallest legal VFR reserve requirements. Many pilots will want twice that.) Maybe you can consider slowing down a bit to stretch the range?

I presume you have worked out some scheme with the FAA to fly the project as an experimental certified aircraft?

It sounds like a cool idea. I’ll be interested to see it fly.

#3

Aiming for SR22 is a bit high IMHO.

Beyond aviation http://www.beyond-aviation.com/ worked on electric Cessna 172 few years back. For some reason they did not succeed. Do you know what problems they had and why they failed? Can you avoid their problems?

#4

Hi Bruce,

Nice to meet you, and thanks for the reply.

Your perspective is right in line with what we’ve been seeing. Most of the general aviation pilots we know need the long range (for example a friend who flies from his home in VA to his parents’ in NJ on weekends), so a reduced range isn’t an ok tradeoff.

We have found missions for which a 200 km limit is fine, but then they’re generally regional cargo routes that require 2500 lb payload … and then a 4 seat GA plane wouldn’t work.

We’re looking for that elusive mission that’s both small payload and short range – maybe it’s out there!

And to answer your question, yes experimental is the way we’ll go, at least at first, until we iron out the kinks.

Thanks again – will keep you posted as we make progress.

Jeff

#5

Flight training would be your ideal mission. Most flight are in the pattern with some short cross country flights thrown in.

#6

Hi Paul,

Funny you mention Beyond Aviation – I’ve just reached out to them and will let you know if I find anything out. The folks involved with that project seem top notch, so I imagine it must be something involving technology or battery limitations a few years back, but that’s just speculation.

Yes the SR22 is a stretch … and it’s also such a safe plane given the parachute that I think it’s a good start. What would you recommend instead? As an alternative we’re also looking at conversions for kit planes, like the RV-10.

Thanks a lot for the reply.

Jeff

#7

Good point – that’s an ideal mission. I think there are at least a few other companies making electric 2 seat trainers (like the Airbus e-Fan and the Pipistrel Watts Up), so I was hoping to find a good mission for a 4 seater so I wouldn’t have to compete with them, but training might end up being the best route. Thanks again – drop me a line if anything else comes to mind.

#8

I think that you need a plane that is light and has a high useful load. Old Piper Archer from 1970s comes to mind. Some have useful loads above 1000 lbs, can fly pretty slow, have “boxy” wings that would be nice for batteries. In case of project failure it would be cheaper than SR22 or RV10.

#9

I think that’s spot-on. The workhorses of the regional cargo industry are planes like the Cessna Caravan, with a high useful load, but they’re also (obviously) very heavy. The Archer looks like a nice choice though. A bunch of that 1000 lb load would be taken up by batteries, so we’re still shy of the 2500 lb requirement by a bunch, but it’s way better than an RV10. Will keep researching – thanks again.

#10

Do you mean that you have 2500 lb of batteries?

#11

My apologies – I was being confusing and referring to something I’d written earlier. Basically I’m looking for the magic bullet mission that’s short range, small cargo, and not training (so I don’t compete with Airbus).

GA is small cargo but needs long range. Regional cargo is short range but needs large cargo. (That’s the 2500 lb reference: the cargo requirements are 2500 lbs or so.)

I think an Archer would be a better choice to start with than the SR22, although I’d love to have a clear use case mission before we finalize the specs … and given the issues above (for example Bruce’s comment), I’m afraid I haven’t found it yet.

#12

I don’t know if there still are, but there used to be freighters made from old PA-32-300 Cherokee Six’es. They had a useful load of around 1500 pounds, 300 to 500 pounds of which was fuel. You would have no fuel, and you would be removing about 440 pounds of IO-540 engine, replacing it all with your batteries and engine. I don’t know what your system weighs, but you might not have to cut too far into the payload.

You can pick up an old fixed gear Six for around $90 to 100K.

#13

Wouldn’t it be a 100% reduction in fuel costs?

Is your 110nm range with a 30 min reserve, or do the batteries die and the plane comes down after 110nm?

#14

If the goal is to get an STC to sell modified airplanes, the Archer is an old and draggy design that won’t sell. The SR22 is a new design, but it’s airframe is designed to fly more like 170K than 120K, where it would be inefficient due to induced drag at lower speeds a battery plane would be capable of. Socata made the TB9, TB10 and TB20 until recently - a more modern and better design than any Cherokee with good load-carrying capability for the engines installed, but they came out after the GA died in 1980 so there aren’t many of them. But maybe enough of them that would get you started. But drag reduction has to be paramount with batteries available to day, so the ideal would be airplane not designed to go too fast (to limit parasitic drag) and that is made of plastic not metal (again to limit parasitic drag). That sounds like a Diamond or maybe an LSA.

#15

To solve your range problem, remove some (most?) of your batteries and put in a diesel generator and some jet fuel.

#16

But that would be heavier and less efficient than the gas motor. You would need something like a 350hp diesel to keep up.

#17

". . . and obviously zero emissions . . . "

Except for where they burn the coal to make the electricity.

#18

But you would have the elusive diesel power without the flywheels, gear boxes, dampeners, special props, etc.

#19

How about a long extension cord? That could be the new meaning of Fly-by-wire![:P]

#20

Jeff,

You are facing the same challenges the electric autos are facing. Range Issues and weight. I think you are 2 generations in battery technology away from a viable solution.

I also think like in cars, trying to convert an existing airplane is wrong. Needs a clean sheet design.

Also, right now trying to talk to the FAA about batteries is a non-starter. The Boeing Dream-liner ruined it for a while.

But keep dreaming. Aviation is good at that.