# Will 'Bye Hawk' Electric Airplane Transform Flying?



## EVDL Archive (Jul 26, 2007)

Dustin Charapata highlights work on all-electric Cessna 172 Skyhawk airplane.

More...


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## pete c (Feb 26, 2011)

Interesting idea, but, IMO, very impractical, for a very simple reason.

Extra weight in an aircraft is a very, very, very bad thing. In a terrestrial vehicles it just slows you down a bit and requires a slight bump in power. On level ground, the power increase needs are minimal. In an aircraft, every ounces means more power requirements, which means more battery, which means more power......

You get the idea.

E-planes make sense in unmanned, very light applications. Add one of us fatasses into the equation, not so much.

If we ever see energy storage levels that make batteries anywhere in the same ballpark as fossil fuels, this could change. Sadly, I don't see that happening in the foreseeable future.


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## Ingot (Feb 25, 2011)

I wish I was good with numbers, but I'm not..

Max weight of the Cessna is 2,200lbs and it burns about 7.5-9.2 gallons of fuel per hour. So.. like 252kWs ... burned an hour? X: Probably doing that entirely wrong.


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## pete c (Feb 26, 2011)

Ingot said:


> I wish I was good with numbers, but I'm not..
> 
> Max weight of the Cessna is 2,200lbs and it burns about 7.5-9.2 gallons of fuel per hour. So.. like 252kWs ... burned an hour? X: Probably doing that entirely wrong.


Not too good at numbers either, but, i think you are getting at the same point I'm making. that cessna's gonna get heavy real fast and it's fuel usage will go through the roof.

bottom line is, carrying enough battery to get the thing off the ground for 5 minutes will be quite an accomplishment. Anything much beyond that will be a miracle and not a very cheap miracle at that.


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## ElectriCar (Jun 15, 2008)

I think it holds about 20 gallons in each wing. Av gas weighs 6lbs/gallon. The problem I see is space. However with cylinders for a pack vs prismatic batteries this thing is very doable. That's about 4 hours flying at around 120mph. 

When I flew a lot, I did a calculation of miles per gallon on a Tomahawk made by Piper Aircraft. It's smaller than this plane but IIRC it averaged about 21mpg. It could fly using as little as around 4.5gal/hour I think but it's cruise was around 100mph I think. That was in the late 80's which is why I'm saying "I think" a lot but I recall the mileage being 21 very well because I was shocked it was that good.


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## PhantomPholly (Aug 20, 2008)

Might want to re-think those numbers - you wont be seeing 4 hr flight in a Skyhawk any time soon.

A better use for electric power in airplanes in the near term will be self-launching gliders.


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## ElectriCar (Jun 15, 2008)

Oh no I didn't mean on batteries it could fly 4 hours, I meant the gas model could. With it's weight in fuel of about 240 lbs, you're limited severely in pack size. What I was thinking was using small cells you could maximize the available wing tank space for batteries. I have no idea how far it could fly but I suspect it could easily make a flight for an hour, maybe two. I'm really interested in how this develops.


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## PhantomPholly (Aug 20, 2008)

There is plenty of open space inside the wings of your typical SkyHawk; weight is definitely the enemy.

These planes typically get the equivalent of around 15mpg - worse than a pickup truck. My guess is that current batteries using the same weight as the fuel would only power it for 20-30 minutes; maybe even less as they would be running at high C ratings.


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## drivin98 (May 9, 2008)

PhantomPholly said:


> A better use for electric power in airplanes in the near term will be self-launching gliders.


There is an electric self-launching glider for sale now. The company has sold at least 20 this year, so far.

There are a few electric airplanes out there but I think the Cessna airframe doesn't really lend itself well to this type of propulsion. Guess we'll see.


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## TraxXxstaR (Feb 8, 2011)

Having read through this, I'm wondering if anyone has tried to do a weight in/weight out calculation. 
Clearly batteries would be heavy but so are aircraft engines. 
An EV motor HAS to be lighter than one of those things.


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## aeroscott (Jan 5, 2008)

I though that I read a detailed article on the Bye hawk a month ago there . did a search , no luck . But as I remember , new 5 blade prop (lighter) engine weight 350 lbs reduced to under 100 lbs for E motor , then they used the motor weight saving plus the max fuel weight to get the weight of the battery (Li-poly) to get 2 hrs. flight time that would be good for training . that would work for me to commute to bay area (40 min. flight).


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## PhantomPholly (Aug 20, 2008)

TraxXxstaR said:


> Having read through this, I'm wondering if anyone has tried to do a weight in/weight out calculation.
> Clearly batteries would be heavy but so are aircraft engines.
> An EV motor HAS to be lighter than one of those things.


I thought perhaps so, too, until I learned a couple of things.

#1 An aircraft engine spends 90% of it's working life at or above 65% of full rated power; typically runs at 75-80% power; and should be able to sustain 100% power for at least 10 minutes. This contrasts starkly with automobile engines which often spend 90% of their lifetime under 40% power and only need 100% power in bursts.
#2 An aircraft electric motor and its associated controller, etc. cannot create any significant electrical noise that would interfere with radios and sensitive navigation equipment in close proximity

A 210hp Lycoming 4 cylinder motor can endure 100% power continuously (in theory - in practice it requires more frequent overhauls), and weighs around 350 lbs installed (fuel injection system; alternator; propeller governor; fuel pump; fuel filter; etc. but not counting the propeller). Go look up electric motors that can put out 200hp continuously, and I will assume that they must be brushless to avoid serious EM.


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## aeroscott (Jan 5, 2008)

there would be great safety advantages , carb icing , water in fuel and much higher emergency power . I have lost many people to the first two .


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## drivin98 (May 9, 2008)

There was a story on AutoblogGreen about this effort.


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## aeroscott (Jan 5, 2008)

was just watching Direct TV (NGW) about flying Africa south to north . The more north he went the harder to get and more expensive the av gas becomes $11/liter or $2,200/drum . and spending days looking for it.


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## PhantomPholly (Aug 20, 2008)

aeroscott said:


> I though that I read a detailed article on the Bye hawk a month ago there . did a search , no luck . But as I remember , new 5 blade prop (lighter) engine weight 350 lbs reduced to under 100 lbs for E motor , then they used the motor weight saving plus the max fuel weight to get the weight of the battery (Li-poly) to get 2 hrs. flight time that would be good for training . that would work for me to commute to bay area (40 min. flight).


I would be interested to know the maximum continuous hp they are getting from a 100 lb electric motor. Based on the Warp 11 as a rough guideline I would think it is no more than 50hp continuous for a 100lb motor. That would be enough to keep a Skylane airborne, but not moving very fast.


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