Electric Ultralight Aircraft Project

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Joined: 07/05/2010
Points: 3

My name is Alex Kimmell. A friend and I have been looking at Ultralight aircraft, and are planning on building one. From what we know, all Ultralights have been built to be Monoplane aircraft with gas engines, but we would like to mix it up a bit. Dispite our age of only 13, we have undertaken the task of building a Electric Biplane to sail the skies with! Although, I am need of some help.

Our Original Plan:
Originally, we had planned on sticking two high torque electric motors and four car batteries in our aircraft, and varied the speed of the aircraft by switching the number of batteries supplying power to the motors, but through farther research, I am finding the plan a little impracticle.

I am looking for some help with finding some 12v batteries that are able to power two motors at a good RPM. I am also looking for two motors that can power an Ultralight Aircraft.

Our problem is finding the Motors and Batteries to power our aircraft.

Ultralight Aircraft Guidelines
These must be followed to build an Ultralight

Single occupant only for recreation or sport purposes with 5 gallons maximum fuel.

Unpowered free flight empty weight under 155 pounds or powered weighs under 254 excluding floats or safety devices.

55 knots maximum calibrated airspeed at full power in level flight, power-off maximum stall speed 24 knots calibrated.

Can be inspected by FAA to make sure it meets criteria as an ultralight.

Vehicle not required to meet any airworthiness certification standards

Pilot not required to meet any aeronautical knowledge, age, or experience requirements to operate or to have airman or medical certificates.

Not required to be registered or to bear markings of any type.

No operation is allowed that creates a hazard to other persons or property.

Only operate between sunrise and sunset unless equipped with a suitable anti collision light extending flight time to twilight periods 30 minutes before sunrise and 30 minutes after sunset.

Yield the right-of-way to all aircraft and not create a collision hazard with any aircraft.

Do not operate an over any congested area of a city, town, or settlement, or over any open air assembly of persons.

All operations are conducted in uncontrolled airspace unless prior authorization from the ATC facility to operate in within Class A, Class B, Class C, or Class D airspace, or within the lateral boundaries of the surface area of Class E airspace designated for an airport.

Must comply with flight restrictions in the proximity of certain areas designated by Notice to Airmen (NOTAM) and Temporary Flight Restrictions (TRF).

No person may operate an ultralight vehicle except by visual reference with the surface.

Visibility and cloud clearances similar to general aviation airspace.

If anyone could help me with this project it would be greatly appreciated.
Thank you

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reikiman's picture
Joined: 11/19/2006
Points: 8444
Re: Electric Ultralight Aircraft Project

I hope you found some information on energy density as "car batteries" are not practical in this application. You want the highest energy density you can get to have the lightest weight to enable liftoff. See Battery pack power density and energy density The measurement of importance is kilowatt-hours per kilogram. Lead-acid batteries like the typical "car battery" have the lowest energy density. The highest energy density is lithium-polymer.

For the motor choice you're again going to be looking for energy density. I'm not sure of the units but the desirable one gives more torque per kilogram than other motors. Or something like that.


- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
- Electrified Electra Townie, 1971 Karmann Ghia (since sold), Kia Soul EV

Joined: 06/19/2007
Points: 72
Re: Electric Ultralight Aircraft Project

The Easy Riser was a popular ultralight biplane design from the late 1970's. Here's a picture:


Joined: 05/27/2010
Points: 220
Re: Electric Ultralight Aircraft Project

http://www.units.muohio.edu/dragonfly/flight/index.shtml This link will give you a good feel for what you need to build. The Experimental Aircraft Association will be thrilled to help kids build. They'll also take you flying. EAA Young Eagles. Ahh, to have had so much available to me as kids today do, but instead they play video games.

My first suggestion is: Dump the biplane idea. A wing works best when it's in clean air. To have two wings so close together affects the flow of the air over the bottom wing and under the top one, reducing their effectiveness. A triplane has a pretty much useless wing in the middle. The only reason they continued to tolerate the biplane even though the first monowing planes flew just a few years after the Wright Brothers is for structural soundness, the feeling than the two wings made a stronger airframe. They soon realized that was overrated. When you decrease the effectiveness of the wing, you necessitate a larger wing, making it heavier and requiring greater airspeed and horsepower to make up for that. The reason that gliders have such long, narrow wings is because that's the most effective wing, although that's not strong enough for higher speeds. You need to go with the most effective concepts available.

70 ULTRALIGHT AIRPLANE HELICOPTER HANG GLIDER PLANS: eBay Motors (item 390214843680 end time Jul-10-10 12:44:05 PDT)

If you want to stick to simple projects, there's ultralights like the Don Quixote in collections like this that aren't that hard, but it's the same thing everyone else is building. And yet still plenty hard for you to do. If you'd like to do something even better. . . .

Let me point you in the perfect direction: If your ultralight could fly on human pedal power, it should ten be able to fly on electric power, right? So you should look at the two aircraft that led to the Kremer prize winner, the Gossamer Albatross and the Gossamer Condor. Mentioned in the first link.

Both flew in "Ground Effect." When your wings are closer to the ground than the wingspan, they become very effective in generating lift. This makes it easier to land without hitting the ground. But these pedal planes got off the ground and stayed close in the additional lift of ground effect. Theoretically the pilot was pedaling to generate less than a 300 watt motor would provide. But can you add an electric motor, and even some light LiFePO4 or the like batteries, (Do as the moderator tells you.) and wind up at the same weight? Probably not, so you start planning to be heavier, and you'll have to travel a bit faster.

Mike Sandlin Airchair Ultralight Glider Plans

Airchait technical drawings

XPlane simulators for these designs

So I obviously intend to offer 2 cents upon 2 cents, so let me tell you what I want you to build. (And maybe I should get to work and beat you to it.) Imagine if that Gossamer series of pedal gliders were to have added a pedal assist electric drive. Perhaps people here have suggestions for one that's available at maybe 500 watt. It's not too outlandish a thought that a manufacturer would GIVE a couple of kids a full set for such a project. (Perhaps someone here is connected.)

If you wanted, you could also get a book that could help answer questions, but I don't think it would be required reading. Simplied Aircraft Design for Homebuilders

Oh, there was also a solar powered Gossamer Penguin.

Human powered aircraft lair

Human Powered Ornithopter

On This Day: The Gossamer Albatross Flies Across the English Channel

Gossamer Albatross Photo Collection


Don't fly any higher than you're willing to fall.
-Michael Sandlin (Pictured)


WHo dares, WINS!!!!

Joined: 11/22/2006
Points: 1380
Re: Electric Ultralight Aircraft Project

I know of one manufacturer of an electric trike-type ultralight meeting FAA Part 103 (as you described) as well as heavier FAA experimental or light-sport category electric planes that you would need a private or sport pilot license. It is called Electra-flyer. Presumably they come in kit form - either trike and wing or just the trike and you find your own suitable wing.

Lead-acid batteries are far too too heavy. Lithium Polymer cells are used for the Electra Flyers.

If you are set on a rigid-wing 3-axis airplane (not a hang-glider-type flex wing trike), then Electra Flyer also sells just electric propulsion kits which could be adapted to a Quicksilver or similar ultralight.


The prices for even just the propulsion kit, batteries and prop give me sticker shock, though. Save your money. I'll probably stick to flying cheap used hang gliders off our local Pennsylvania ridges myself.

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