Friday, April 22, 2011

Electric Flight: More Thoughts

Yesterday a reader commented on my electric flight post, specifically about the LZ FES, a pretty sexy add-on that just won the Lindbergh LEAP prize for best new electric propulsion system.  He wondered whether electric flight for now required light weight motorgliders or whether heavier, 15M plus sailplanes/motorgliders would be workable for electric power.
My answer began to get too lengthy to stick in comments so I'm posting it here, and thanks Thomas for your enthusiasm.

I talked over this very subject this week with Randall Fishman, the award-winning electric flight pioneer.  His take on where we're at right now is in my Profiles in Vision column, coming in the July issue of P&P.
Randall's whole trip is to get people up in the air with electric power right now, and not for 150,000 clams either.  To summarize his own one-man research and development plan, it's all about lightweight motorgliders.
There are two key factors -- light weight and a good low sink rate.  The less power you need to get airborne and maintain flight, the better contemporary electric flight technology works.
Randall hopes to debut his latest design, a composite two-seat LSA called ElectraFlyer X, at Oshkosh this year.  It's a very cool looking airplane...and a motorglider.
Previously, as I've noted here more than once, he rocked the electric world with the ElectraFlyer Trike, currently available for sale, and the prototype ElectraFlyer C, a single-seat model (more below). He's also in test mode with newly designed motors he's had built for the X and other projects.
There are lots of other electric motorglider projects out there, for this basic reason: the less amount of thrust you need to stay airborne, the more viable electric propulsion is.  For now that has to mean less transportation-style flying and more "pure enjoyment" local flying.
Can we live with that?  Hell cool is it that we are able to fly this completely revolutionary technology right now?
My favorite story of Randall's recounts the time he took his electric trike off from Ellenville, NY's little airport, motored over to where the hang glider guys were soaring the popular ridge a couple miles away, turned off the motor and joined the thermaling gaggles.
Typically, and I've done this myself, you work up into ever-stronger lift bands at E-Ville by ramping  up the sloping ridge, which can get you good and high but also back half a mile or more from launch.
That particular day, some guys were way high but way back.  Randall, because he had the boost of electric power when he needed it, was able to penetrate out in front of the hill and catch some really strong lift that the pure soaring craft couldn't risk trying to reach for fear they'd land out from the LZ, the landing zone.

He flew two hours that day -- and landed with plenty of "juice" to spare.
This is one highly doable scenario for electric powered flight.  No, it's not 100 knot A-to-B flying, but we've got plenty of gas-powered aircraft for that already.
The Electric Swift.  Photo from Icaro.  No, that's not a tail, but a folding prop!
This is something new, but also old: flying again for the pure joy of it...without the many detriments of gas engines.
On a good soaring day, you can take a current-tech electric, whether it's a hang glider trike or a lightweight motorglider or a flying wing like the Swift at left, motor up into the lift, and fly as long as the lift holds out.  That's possible right now.
And to repeat my electric-flight mantra: no mess, no smell, dramatically less noise, no vibration, no annuals, no oil, no gas, long-life motors, rechargeable battery packs that cost under a buck to charge, and will last many hundreds of hours, and will get increasingly affordable as more people jump on the electric bandwagon, not just in the air but also for ground vehicles like cars, bikes and cycles.
We're in the beginning stages of a paradigm shift that will outlast all the greed-based attempts to forestall it.  It's here, it's growing, and it will be glorious.
Okay, down with the pom poms and back on topic.
There are more pure "muscle" electric aviation projects out there as well, of course.  Before those become reality, before the "higher, faster, more payload" visions become reality, battery efficiency will have to improve by a few scales of magnitude.
Electric Swift's cockpit view.  Photo courtesy Icaro.
So the answer to your question, Thomas, about electric powered flight right now, remains with lighter weight and more efficient airframes, and that spells motorgliders.
Bigger motorgliders will work but are more exotic and complex to deal with (trailers, special hangars, elaborate feathering/streamlining systems, and higher costs for sure.)
Meanwhile, the electric powered hang glider trikes that Randall and others have developed work, and work very well.
They serve up more than an hour of flight and don't require 130 lb. pilots to do so (Randall weighs 200 lbs. and has consistently had 1 1/2 hour and longer flights.)
Some other notable projects, including the video below, are popping up around the world.  Search for "electric trike" to get an idea.  Here's a link to get you started learning about various electric projects already for sale or imminent.

Let's take a closer look at Randall's ElectraFlyer C prototype (which he is selling for $49,000, see my earlier post).  The C is a single-seat, converted all- aluminum Monnett Moni motorglider he built from a kit.  And Randall also gets 1.5 hours and more on a full charge too, along with 70 mph cruise and 90+ mph top speed.
Manfred Ruehmer's electric trike (see video above).  Photo courtesy Icaro.
Yuneec is of course fine tuning its many electric projects.  Notable are several one- and two-seat motorglider frames, the e-Spyder ultralight, a trike, and a four-seat electric airplane just announced...and all are electric powered.
Some time pretty soon, certainly in the next year or so, we're going to have a lot of electric aircraft on the market, to suit a broad range of budgets.
This will not be solely another rich person's hobby, although it will take time to get the electric industry up and running because important technologies need to be developed and proofed, such as higher-storage batteries and more sophisticated, safe electronic motor controllers.
It is happening.  It is happening now.  We will be flying electric globally in a rich variety of planforms and applications before very much longer, you can count on it.
This year's Oshkosh, in particular, should bring more exposure and new electric aircraft to a broader audience.
Keep a lookout for my survey of electric flight projects around the world, also coming in the July issue of P&P.


Anonymous said...

Thanks for the lengthy posting in response to my question. I have been following the various electric projects with interest.
As you note, motorgliders are an obvious solution to the problem of limited energy. Not only that, but from a gliding point of view the electric motor offers instant-on reliability, which (aside from the other attractive features of electric, like the no-smell, no-noise features), is an absolutely decisive advantage for glider use, but not all that important for airplane use.
As a result, I'm surprised that so many of the electric projects in the works right now are "airplanes" and not motorgliders. Even if they have high L/D they are designed to be operated as airplanes, not gliders - no feathering props, for example. Consider that the Yuneec E430 started off with spoilers, but has moved to flaps for glideslope control, to make it more of an airplane (and there has been no discussion of a feathering/folding prop), What's more, although it's true that Yuneec has acquired a couple of sailplane designs, they don't talk about them much, instead focusing on developing a 4-seat airplane. The PC-Aero design looks like a sailplane, and gets a 25:1 glide like a sailplane, but the designer takes pains to remind us that it's not a motorglider; it's an airplane. Sonex has both airplane and motorglider designs - and they're electrifying the airplane. Greg Cole at Windward Performance is developing an airplane (with very high L/D, yes, but it's an airplane). Bye Energy is building an electric 172.
I'm surprised because, as you say, electric motorgliders and self-launch sailplanes are practical right now, and provide genuinely new capabilities (like mounting the engine almost anywhere on the structure) while electric airplanes are at least 10 years from being practical (maybe more, depending on the rate of advancement of battery technology), and right now fall far short of replicating the capabilities that already exist.
I dimly remember seeing a presentation online (NASA maybe?) that explained why electric made more sense as the aircraft got bigger, for reasons I can't recall. If that's true, it might explain the rush toward larger, heavier designs and why Greg Cole, for example, is not pushing a FES layout version of his Sparrowhawk (which I would have thought would be a neat product) and is instead focusing on getting his Goshawk finished - as an airplane.

Anonymous said...

Agree. The other thing re: motorgliders is that often all we need to achieve is a takeoff to say 3000' AGL. This is what I want, even just one launch before recharge (OK 2 would be better). We don't need the cruise time or distance, or even the "get-home", just the launch please!
Also weight isn't the ugly problem some might make out, many of us fill up with water (100kg plus) and fly all day, sometimes landing with water to save re-filling next day. The improvement in high speed LD is one of the reasons we use ballast. A permanent 50kg or so for a simple launch system is no great penalty for this launch convenience. I'd take it tomorrow!

James Lawrence said...

Too true Thomas, I hadn't thought about that: that significant ballast is a staple of enhancing penetration/glide ratio in soaring flight.
I've read so many comments the last few years on various pages that show how limited our thinking can be about anything new revolutionary...until, like the actor who's knocked around for 15 years, then becomes a star overnight in a breakout role, the tide of change becomes overwhelming and inevitable and everybody's talking about it.
Look as recently as ultralights, which began with someone's desire to hang a chainsaw engine and a 3-foot prop on a 70 lb. hang glider. Look what happened, and is still happening, in that flight realm.
Once the 100th monkey gets the idea that electric flight is for real, we'll stop dressing our desires for electric flight only in terms of Cirrus-like, 160 mph dashes from one airport to another and realize virtually free, fly any way you want electric flight is here.
And unlike what's happened with the price realities of LSA, I believe we'll see at least some very affordable, super-lightweight soaring craft but also local fun flivvers, such as Belite-like ultralights and LSA to help re-dream the very definition of what it means to fly.
We don't have to slavishly reinvent the somewhat monotheistic General Aviation of the last 70 years by simply substituting electric power, although we will see those craft too because they're wanted and needed.
This is a paradigm shift for all of transportation, because, indeed, how badly do we need that?