Hereís what some readers have said
By Patrick Panzera, EAA 555743, email@example.com
Last month I wrote my editorial moments before leaving for the 2010 CAFE Electric Aircraft Symposium. I left with a “skull full of mush” not knowing much at all about electric flight. But I was optimistic, hoping to come home with the proper education to begin seeking out, editing, filtering (the wheat from the chaff), and potentially writing electric flight articles in an intelligent manner. Although I wish that each presenter at the symposium could have given a forum that was several times longer than they did (most averaged 10 to 20 minutes), I believe my educational goal was met. And although I’m not convinced that practical electric flight will be a viable option anytime soon, I would like to sincerely thank all the CAFE volunteers who worked very hard to bring us the symposium, and I would like to offer my gratitude to each of the presenters who were willing to freely share their research and developments.
I won’t be going into any of the details in this article of the things I learned at the event, other than to say that the biggest thing I came away with from the symposium is the fact that the only way electric flight will work anytime soon is through the serious streamlining of the aircraft in which the systems will be installed. Any “successful” electric aircraft flying today either resemble sailplanes or are in fact motorgliders with very streamlined shapes and wings that produce a lot of lift with very little associated drag. This reinforces something I’ve known for a very long time, having a background in sailplanes; general aviation aircraft designers haven’t been giving enough attention to efficient airframes. It seems it was somehow easier to put in bigger engines and larger fuel tanks than it was to make compound curves, fillets, low profiles, and high aspect ratio wings. However, these things were and are prevalent throughout the experimental aviation community of which I’m proud to be a member. And I have faith that the major accomplishments that are needed to take electric flight to the next level and beyond will likewise come from the experimental aviation community.
From our earliest ground school lessons, we learned that drag opposes thrust, and thrust takes power. If drag (either parasite or induced) can be reduced, then so can thrust and the power it takes to produce it. So the best way to increase the economy of a Cherokee is to remove the O-360 powering it and install it in a Cozy and fly the Cozy like a Cherokee.
Or put another way, since the power density of current battery technology isnít great enough to store the needed energy for sustained flight of any substantial endurance, reducing the power requirement by increasing the lift over drag ratio and eliminating parasite drag becomes paramount.
The editorial I wrote last month caused an avalanche of letters to the editor like never before. Here are just a few of them:
I enjoyed your timely article: The idea of an electric plane has so intrigued me over the past few months that I’ve begun self-educating on electricity, motors, and batteries. At the rate I’m going on my Double Eagle project, gas could be $10 per gallon by the time she flies. Great Plains says the 1835-cc 60-hp VW weighs in at 163 pounds, plus 10 gallons of gas at 6 pounds per gallon equals 223 pounds. That’s close to what Ashlynd might put in the Thatcher CX4. Could I fly the relatively light (900 gross) but draggy Double Eagle behind a motor/controller/battery combination at around that weight? That’s the current thought experiment.
Personally, I share your enthusiasm for electric flight and look forward to encouraging news in your report on the upcoming symposium.
It all comes down to what I call energy density: the number of watt hours or BTUs [British thermal units] per pound of battery or gas that you have to carry.
For airplanes, weight is everything. Think how many airplanes today have useless loads; they can’t get off the ground if their seats are full or if the tanks are filled for flight duration of more than an hour. Then there is the “refueling” problem.
Depending on the battery type, lead worse than NiMH [nickel-metal hydride] worse than L-ion [lithium-ion], it can take 100 pounds of battery to get the energy equivalent of 1 pound of gas. The Chevy Volt (which has the most sophisticated electric drive system that I know about) will use a 275-pound L-ion battery to drive its 40 miles. Some light-sport aircraft can fly 40 miles on 4 pounds of gas.
I’m afraid that electric flight (even though an electric drive system will weigh less than a typical avgas firewall-forward complete package) will not be practical until they are powered by fuel cells capable of extracting as much chemical energy from fuel as exists in gasoline. And this probably won’t solve the carbon footprint problem, as energy-efficient fuel cells will most likely use hydrocarbon fuels.
Forest Hills, New York
In reference to your CAFE Symposium attendance, allow me to save you a trip.
Electric flight won’t work because it can’t work – the basic physics and chemistry are against it. The “energy density” of any plausible combination of battery chemicals is just too low.
That’s not to say there will never be a battery-powered plane, but they will never compete with a combustion engine.
If you are interested in reading more on this subject, I recommend Bob Zubrin’s book The Case for Mars and in particular the section about building Mars rovers.
As from one who has spent years on an electric car project, I feel you may have hit the nail on the head by being leery of what is being said. For years I wanted to build an electric car, so 14 years ago I was in the position to do just so. I had heard that an experimental battery was going to be coming out from a Canadian company that would change battery technology since they would be basically the same price as regular car batteries but would have many times more storage.
I started with an old 1980 Mazda RX-7 which I stripped and added battery boxes front and back and a 100-hp electric motor. All in all, over a year’s time and effort were invested. During the year that it took me to build the car I was in constant communication with the guy that had seen and used some of the batteries but had to send them back since they were experimental. I had come to the point where I was only waiting on the batteries. After a couple of months of trying to get the batteries with no success, I decided to purchase marine deep cycle batteries in the interim.
Needles to say, the batteries have never come to fruition for me or the guy that I had been in contact with. The guy that was trying to get the batteries finally said he thought that someone probably bought the rights.
If we look at history, this kind of thing seems to happen whenever something that could save fuel or divert the use of petroleum products gets in the way of sales of petroleum products. If the batteries had come out as I had hoped, I would be able to drive my car 50 to 100 miles on a charge making it useful for daily commutes. As it turns out, I can only drive about 10 miles at around 30 mph, or I can drive about 5 miles at around 60 – this of course is with regular batteries.
I have been waiting 14 years for an economical battery with enough storage. Some might say, “Well, we now have lithium batteries.” To which I would say, “Yes, we do, but for me to install them it will cost over $30,000 just for the batteries, and that’s if I could even get them.” Trying not to be cynical, I do think someone with way more money than I have can, in the not-so-distant future, build electric planes, but the cost of flying them is going to be out of the reach of the average pilot.
Many of the kits and planes are now so expensive that they are for the elite only. As someone that has been experimenting for years with ideas to increase mileage, I think the future could be best advanced with more efficient engines. Many ideas have come out throughout the years to increase fuel efficiency, but they have been bought up. My hope is that we can learn how to use the fuels we have much more efficiently, which will allow less fuel or greater distance to be achieved. Now that I am retired, I might just be spending a little more time this way!
Thanks for the great article – keep up the good work.
And one last letter, not related to electric flight but probably needs to be addressed anyhow:
I don’t know how accurate the other articles are, but the article about the SD-1 Minisport was misleading! You introduced the SD-1 as a homebuilt ultralight aircraft. The SD-1 is not an ultralight! The size of the gas tank (7.1 gallons) and its cruise speed keep it well out of the ultralight category. I would expect the EAA of all organizations to classify aircraft correctly! I’m disappointed.
Yes, it appears that I used the term “ultralight” a little too liberally in an introduction to a video in the April issue of Experimenter. Here’s the exact paragraph as it appeared:
Tons of fun can be had on a small budget with a small plane and a small engine. Such is the case with the SD-1 Minisport homebuilt ultralight aircraft, conforming to FAI UL and light-sport aircraft definitions. Gross weight: 240 kilograms (529 pounds). Maximum payload: 130 kilograms (287 pounds).
Yep, I blew it. I shouldn’t have used the term “ultralight” when I meant “lightweight.” But in my defense, every word after “ultralight” should cause one to realize that only my terminology was wrong and in fact the plane isn’t a Part 103 legal “ultralight.” One wouldn’t have to click the link and read the article to find this out, so I fail to see how I was “misleading” even with my inappropriate use of the term. But in any case, I humbly apologize and promise to choose my words more carefully in the future. I certainly take full responsibility and seriously hope that the EAA’s reputation won’t be tarnished by my carelessness.
And just so I can end this lot of letters on a positive note, here’s one that made me feel that it’s all worth it:
This is one of the best issues of Experimenter yet. I just loved the format. More and more great topics and suggested reading just kept coming! So many great “rabbit trails” to go down. I felt you all had my interests in mind when writing this. I am a builder, flyer, student, engineer, dad, and husband. To find articles that touch each of those hats was wonderful. I have been considering the CX4 for a build project. After reading the 17-year-old’s story, I am that much closer. I loved his account of the plane. I really like the idea of building one with my son. Thanks again!