Report from EAA AirVenture in Oshkosh, WI

[Lock]

[EVDL] Electric airplanes
Saturday, August 7, 2010 9:57 PM
From: "Rick Beebe" <ric k@bee be.o rg>
To: "Electric Vehicle Discussion List" <e v@lis ts.sjs u.e du>
I spent last week at EAA AirVenture in Oshkosh, WI; the world's largest
general aviation gathering. Electric aircraft were very much a presence.

There was an electric aircraft symposium with lots of interesting
speakers talking about the trials, tribulations and future of electric
aircraft. There were presentations on aircraft design, motor design, new
batteries, and controllers.

Yuneec (pronounced "unique") Aircraft was there with two machines. An
electric ultralight and a two-seat Light Sport aircraft. I think the
first is a good example of machines that work well within the current
electric limitations. The ultralight will run for an hour on a charge.
That's sufficient for most users and ultralights usually return to where
they took off. Ie it's rare for people to travel places in them. They
also have an electric back-pack powered parachute. That might be really fun.

Their light sport plane can fly for 1.5 to 3 hours but I suspect "range
anxiety" will limit the appeal.

Pipestral USA was showing off their Taurus electric moto-glider. Another
example of a reasonably good application for electric.

There were a couple kit plane manufacturers showing off prototype
electric power plants for their kits. Sonex was one, though they seem to
be devoting more time this year to their micro-jet powered plane.

Sikorsky unveiled a test-bed electric helicopter. It's a Schweizer
S-300C with a honkin' big (about 20" diameter) 190hp motor from U.S.
Hybrid and 370V of lithium cells from Gaia. It'll only fly for 15
minutes or so (they haven't flown it yet) but they're using it as a
technology test. In this case they just replaced the ICE with it, but
they had some interesting diagrams of making a motor integral with the
rotor-head. That raises all sorts of possibilities for simplification of
the drive system. No gearboxes, no sprague clutch. I actually think
that, combined with a small battery pack and a turbine/generator could
make a fantastic drivetrain for a helicopter. In general, helicopter
rotors want to run at a constant speed (around 500 rpm) and it's easy to
make a motor do that.

Flight Design showed a hybrid plane. A small(er) fuel-efficient ICE with
an electric motor to give it help on takeoff and climbs. And if the gas
motor dies, the electric will run for 10-15 minutes to help you get to a
landing spot.

Anyway, there was lots of exciting stuff happening. A full list of the
forums presented (no, I didn't get to them all) is at
http://www.eaaapps.org/forumsearchresults.aspx?interest=46


--Rick

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[wheelbender6]

I would do a lot of autorotation practice before taking off in an electric powered helicopter.

[Lock]

Sooo... "autorotation"... another word for regen?

Lock

[mat h physics]

I would certainly rather fly an electric helo, than plane. Autorotation makes it much safer to land w/o power.

[etard]

Anybody seen the motor on the Sikorsky yet? This video shows a glimpse of it, built an hour away from me.

[Jeremy Harris]

When I first saw that Sikorsky electric demonstrator the thought that went through my mind was about getting free charges.

Helos are often used for power line work, as they can lower a linesman on to a high voltage cable whilst it's still live, to do maintenance work without turning off the power. The thought I had was that if you got low on charge you could just hover over a power line, drop a couple of dangling cables and hook up to a 400kV power source for free...............

Jeremy

PS: I know it's a crazy idea, one that would be accompanied by a bloody great flash and bang, but it seemed amusing at the time.................

[flyinmonkie]

I would certainly rather fly an electric helo, than plane. Autorotation makes it much safer to land w/o power.

Are you joking? Autorotation is tricky to get right and a hard maneuver anytime. Helicopters have a glide ratio of... well basically zero. An airplane on the other hand becomes a large heavy glider when the prop stops turning, but it does glide. And if you are high enough you can go a long ways. Better to become a heavy glider than a rock when the blades stop turning.

[Jeremy Harris]

I would certainly rather fly an electric helo, than plane. Autorotation makes it much safer to land w/o power.

Are you joking? Autorotation is tricky to get right and a hard maneuver anytime. Helicopters have a glide ratio of... well basically zero. An airplane on the other hand becomes a large heavy glider when the prop stops turning, but it does glide. And if you are high enough you can go a long ways. Better to become a heavy glider than a rock when the blades stop turning.

Not that hard to do and something routinely done in training and during check flights. Glide angle in autorotation isn't bad, either, typically around 17 degrees or so, with maybe 60 to 70kts of forward speed. Autogyros are in a state of constant autorotation all the time they fly.

The only very slightly tricky bit is the response time from recognising an engine, transmission or tail rotor failure and dumping the collective to retain Nr. The failure has to be spotted and action taken quickly to avoid Nr decaying too much, particularly on something with a low inertia rotor, like a Robbo, as once it decays below a critical speed it can't be accelerated back up from reversed flow. Once Nr is up in the safe zone (typically around 105%) you can trim forward speed with cyclic and adjust Nr with collective to get best glide and descent rate.

To be honest, there's little to choose between fixed and rotary wing in terms of options if the engine fails (I've flown both). Fixed wing you have a longer glide distance to find a safe landing spot, but have to accept you're going to land at speed in a spot that might be too short or have obstructions and you may not be able to land into wind to reduce your ground speed. Rotary wing engine failure means less glide range, but you can trade Nr for forward speed as you land, so very significantly reducing the size of safe landing area needed. Some helos will carry enough rotor inertia for you to be able land vertically from an autorotation with a normal landing descent rate.


Jeremy

[TylerDurden]

Best of both worlds?

Mail-Gyro.jpg (189.94 KiB) Viewed 1195 times

(No "pushers" for me, thanks.)

[liveforphysics]

I would certainly rather fly an electric helo, than plane. Autorotation makes it much safer to land w/o power.

Yep. Even in an RC heli, as long as you have enough elevation when you cut power, you're golden. You can land as soft as a feather with no power.

For me, if I could choose between running out of power in a rotary-lift craft or fixed wing would depend entirely on the area I was flying. Flying in Nebraska or any of the other flat as a board area, give me a plane, everywhere you look is a landing strip. Flying over wooded choppy hills and valleys, that helicopter would be looking pretty nice. It's a lot easier to find a 30ft area with only light foliage that you can autogyro towards, and flare at the last second than to find a makeshift landing-strip with a decent approach in a hilly forest.