Electric Airplanes
 

Here's one electric airplane:

http://www.wired.com/images_blogs/au...05-660x303.jpg
(click on image for link)

Here's another:

http://3.bp.blogspot.com/_imIrRbm3PM...aircraft-1.jpg
(click on image for link, including video)

...I can just see it now--a stewardess frantically running up & down the isle asking passengers if anyone has any spare BATTERIES whenever their airliner has to go into a "holding pattern" around a busy airport!

what is the effect on weight and range and power?

Oh, wait, it is a tiny fraction of liquid fueled, like so many electric cars that go 40 miles. I bet it costs a fortune too. They can have it put out the same power for a tiny fraction of the range or some other combination of a fraction of liquid fuel capabilities.

There's lithium, right next to ZERO on energy/mass and energy/volume...
http://upload.wikimedia.org/wikipedi...ensity.svg.png

Somehow I doubt that :-) Even if electric airliners someday become practical - well, does the cabin crew run around asking passengers if they happen to have any jet A on them when a flight goes into a holding pattern nowadays?

Even now, there are places where electric airplanes could work, starting with (as mentioned on that other thread) self-launching sailplanes. Then there are possibilities in the Light Sport class, where you may never travel long distances. When you figure that 100LL avgas is now $7.09/gal at my FBO (plus a quart of not-cheap aviation oil every 10 hours or so), and that a major overhaul of an aircraft engine was IIRC about $12K over a decade ago (about $16K now, from a quick search), electric power for sport flying begins to look kind of attractive.

Then too, as with the Tesla, there are people to whom the impact, environmental & otherwise, of burning oil is more important than money.

I'm pretty sure that chart is taking the energy of a lithium ion battery its self, not one fully charged with electricity.

My Li-Po race cels are lighter than my Li-Fe's and you've got to remember with electric there would be little differential between take-off and landing weight and you could dump all the fuel pressurisation/cooling sytem just think of the turn around time if it was a cell exchange at each air port rather than a charge!

electric power has taken over in the remote control airplane hobby

Not sure why you think that. Can you offer any supporting evidence?

per: Lithium-ion battery - Wikipedia, the free encyclopedia
Volumetric energy density: 250 to 620 W·h/l (900 to 1900 J/cm³)[2]
1000 cm³ = 1L
~2MJ/L energy density for lithium batteries, which is about what was plotted, compared to ~37MJ/L for diesel.

That is another disadvantage of electric plains, the batteries still weigh a ton when they are depleted, whereas your fuel tanks do not. Dead weight on a plane translates into inefficiencies, you have to create more lift, which doesn't come for free.


Great, just make sure the airports are spaced 10 miles apart so you can make it to the next one ;)

Indeed, such toys, that have no need for payload that run for maybe 10 minutes (well I usually catch a thermal or two also), do not need to be uber efficient. There are still a lot of fuelies left when the pilot is serious about performance.

As an aside, excellent performance can be had with NO motor too (and extra weights are usually needed), though around here I just bungee launch:
http://www.youtube.com/watch?v=Oix6sHKzOLU

What I find funny about that video is the RC jet guys are lucky to push 360mph
http://www.youtube.com/watch?v=dTHWBSluUjU . Maybe you get 200mph with an electric RC, and the no-motor plane serves them both up for raw top speed (and endurance and efficiency and cost) under the right conditions :)

At least at my local air port most people with small private planes don't take them on long trips and that plane has a 140 mile range, so you are good for a trip to a cabin or taking someone on an air tour of the area and the best part is, if you have your own air strip... straight section of road or field, you don't need to get fuel deliveries there any more, you just need a 220v outlet.

It also sounds like these planes cost about the same as the gasoline counterparts but are much simpler so when you get your annual inspection done you get your electric motor checked and maybe bearings replaced compared to a gas engine plane that gets it's engine tore down and rebuilt.

re: 140 miles
per FAR 91.151, planes cannot take off without 45 minutes reserve flying time beyond their destination at night (30 @ day but we should look at worst case). That is for VFR. So assuming the lower limit of 90 minutes flight time (@ 70mph) you should plan on being at your destination within 45 minutes of flying, even if you are landing where you started. So that you could go 26 miles out and 26 miles back if you leave late in the day. Even if you assume 30 minutes reserve for daylight and VFR, that is still 60 minutes on the inside of flying time or 35 miles out and 35 back. Forgive my hyperbole of 10 miles.

I understand the local applications of this, and there is certainly some envelope of operation where it could make sense, but it is competing directly with potentially more efficient/affordable ground transportation at these distances, not for commuting in the general sense certainly.

But I am very concerned that john Q. public (and the folks looking for startup money) will not understand those limitations and think that we are on the verge of replacing all liquid fueled aircraft with batteries. 99.9999% of the public thinks of airliners when they think of airplanes, and of closing large distances in a small amount of time, because that is what they use when they buy passage on an airplane.

I also appreciate the reliability/durability concerns, and I hope that brushed motors are not on the table for the same reason. But a turboshaft could close the gap fairly well too and still offer high energy/weight and high energy/volume, both of which equate to more payload for way more miles.

Make no mistake, I would love to have one and a backyard big enough for it if it were handed to me, but if I'm getting in a plane it is usually to go a considerable distance (i.e. significantly over 400 miles). And propellors can still make quite a racket.

Making a large passenger plane that is all electric is a rather silly idea, just like it's silly to try to build an all electric semi truck or school bus, but for light duty use an electric plane is really tempting, I didn't know about the 45minute rule so that does cut back on the usefulness but I'm sure there are still people out there where this would be the correct tool.

...and, now, reversing roles for a moment and playing the "Angels' Advocate":

How about a solar-powered airliner, that uses batteries for "reserve & emergency" power? Coat ALL the upper body and wing surfaces with solar-cell material instead of paint!

There have been a few flimsy solar powered aircraft, and it wouldn't hurt to put them on here either if you are flying 45 miles away somehow to no power and can wait a few days for it to recharge, but I don't expect much contribution for the duration of a "normal" flight, unless you slow down to the speed of a bicycle or something and have one not-too-heavy passenger and no payload.

All timeframes above are complete swags.

Here is another one, I forget how fast, maybe 25mph or something on a slight decline...
http://www.wired.com/autopia/2011/05...tional-flight/ Initial scan of the comments seems to be in agreement with what I'm trying to say. 100+ million dollars for 25mph?

You're still trapped in the box of thinking of the airplane as a way to get from A to B. There are both practical & recreational reasons why you might also want aircraft that would do something different. As for instance this solar powered one: park it at 30,000 feet and it could circle for years (with robotic pilotage) doing surveillance or acting as a cell phone relay.

Or again, the recreational market. I don't suppose that in all my sailplane flying, I ever got much more than about 10 miles from my starting point, so fuel/battery capacity is pretty irrelevant, as long as it's enough to launch and get into a thermal.

Lol, you want me to consider your special case where you always fly back to where you started and you call me trapped? THAT is funny... If this isn't about efficiency then it belongs in another forum, i.e. the lounge.

Are you kidding me? Have you ever tried to fly something with a five foot wingspan going that fast? You can only fly straight for a second or so before you need to turn around so you don't lose it. That's not even fun anymore. The AMA in the US won't insure anything over 200mph.

Pretty cool video.

OK, so how much time have you logged in sailplanes, or in a single engine aircraft? I have a couple of hundred hours sailplane time, a bit under 2K total, and have owned my own (well, 4-way partnership) Piper Cherokee for going on 20 years.

With sailplanes, you mostly do return to your starting point, unless you're doing some sort of competition. Similar with small planes: if you're just flying for fun (or for training), you might go up for an hour or so, then return to where you took off from. You can argue all you want, but that's simply the way it is.

A speed record in a (tiny) electric airplane:

http://www.blogcdn.com/green.autoblo...ane-record.jpg
(click on image for link)

lol @ james, let me know when you finally come up with a problem for this "solution" :) Keep trying though, and explain why you like dead weight and lots of initial expense over any other available options.

30mile range, before FAR 91.151, which means 0 mile range here or negative 15 mile range at night (60mph assumed). 175 miles per hour max, meh, tell me when this isn't a stupid idea. The battery probably weighs 70lbs, then add motors etc.

Get a motor glider like http://www.eel.de/images/pdf/ULF-2_e_neu.pdf and spend that 70lbs in fuel and you can cruise at 62mph for 11.6 HOURS for a range of 700+ miles.

IF you guys really need a toy, go for it, run and get your checkbooks now, but efficiency for utility is next to zero. There are severe limitations on power to weight/power to size for batteries and they are even more pronounced in an airplane than in a 2 or 4 wheeler. The gap is so huge in fact that there is little else to do but laugh at folks taking this seriously.

IF you cannot be bothered to load up a trailer of 55 gallon drums to have fuel on site solely so you can fly in small circles away from fueled airports, but near an air strip with sufficient power to recharge your plane quickly, then this is the plane for you.

Another electric airplane; obviously from a company that doesn't know what they are doing:

http://www.blogcdn.com/green.autoblo...e1-660x357.jpg
(click on image for link)

They know what they are doing, trying for 1.3 million in prize money while working with funds from airbus. It carries 2 gallons equivalent worth of gasoline in batteries that cost more than perhaps you and I combined will ever make. And it is competing in another x-prize style contest with electrical bias via pMPGe now? 2011 GFC FAQ

You tell me Neil, from an engineering perspective how does it make sense to make airplanes heavy with low energy to weight ratios?

Also, wtf does this mean? This has to be the most pointless contest I have ever heard of. You can enter, get 200mpg and they can say "sorry"?
Q #23: How will CAFE measure fuel or energy use? Will it be strictly by weighing?

A: CAFE reserves the right to use methods other than weighing to measure fuel or energy consumption, depending upon the aircraft design. (rules, p. 24, 38)

So, if they like electric, they will use really wonky numbers for pMPGe (wtf is that too?) This isn't about efficiency with rules like that.

One of the documents on the site (which is now not directly inaccessable) by a mr Gremban, indicated that he thought it would be won by a glider like diesel fwiw:
http://docs.google.com/viewer?a=v&q=...iJnOAFyA&pli=1

If you want to do it for recreation, fine, or have a runway in your back yard and an outlet, and lots of mula for a battery, great. You will have to keep the range short to not have a serious performance penalty of course. But everything else being equal, it is worth shlepping a couple gallons of biodiesel around IMHO, for the foreseeable future.

And if this is about mostly inefficient recreational use, for the bourgeois, then why should the rest of us care?

They got up to 400MPGe per passenger and have a range of about 300 miles.:

Pipistrel wins $1.35 million in Google-sponsored 2011 Green Flight Challenge

...interesting propellor-blade "shape" on that Pipistrel.