AvWeb recently ran two back-to-back reader polls that produced some surprising and interesting results. I thought these might be worth discussing.
First off it is worth noting that these AvWeb polls are "non-scientific", in that the participants are "self-selected". People not interested in the issue probably won't take time to answer. Also the respondents might be from anywhere in the world and therefore may not represent Canadian or even US fliers.
Here are the complete results to both polls, as of today:
At what fuel price (if any) would you quit flying? (Choose the answer that's closest to your personal limit.)
They're already too high. (And I've already quit.) 28%
$7 a gallon 14%
$8 a gallon 10%
$9 a gallon 13%
$15 a gallon 12%
I could never quit, no matter how much I have to pay for gas. 24%
What would be the minimum acceptable speed, climb rate, cruise speed, payload and flight time endurance acceptable to make you consider owning a battery-powered electric airplane if it cost under $150,000? (Remember that fuel and maintenance costs would be greatly reduced!)
500 fpm, 60 kt, 200 lb (single seat), 2 hr 2%
500 fpm, 60 kt, 400 (two-seat), 2 hr 7%
500 fpm, 120 kt, 400 lb (two-seat), 2 hr 19%
500 fpm, 120 kt, 400 lb (two-seat), 4 hr 38%
1000 fpm, 180 kt, 800 lb (four-seat), 4 hr (and I might be willing to pay more) 18%
I would never consider an electric airplane. 4%
OTHER (My opinion doesn't appear as a choice.) 11%
As can be seen from the two questions AvWeb asked, one of the biggest issues facing aviation in 2008 is the price of fuel. With the loss of the value of the US dollar and the increase in the price of a barrel of oil, gasoline has doubled in price in the USA over the past twelve months and looks to keep going up for the forseeable future. In some parts of the US lower states 48 avgas is already around $7.00 per gallon.
What is surprising about this poll is that the largest group of respondents is those who chose the first answer - "They're already too high. (And I've already quit.)" If you account for the fact that avgas is already close to $7.00 per gallon, which was the second choice, then the number in that category is probably 42% of US pilots, which is a staggering number. My first thought is that if you think aircraft were cheap this spring, wait until this fall if all those pilots and owners are quitting and selling their planes!
The number of people who say they would quit flying at $8, $9 or $15 per gallon is fairly even, and then you get to the second biggest group - "I could never quit, no matter how much I have to pay for gas." Upon reading that I found it hard to believe that there really is no price that is too high to pay to keep flying for 24% of respondents. I wondered if perhaps it was just an emotional response. Then I thought about it and concluded that they are probably being honest there. They will always fly but will cut their hours down, at least until they are flying just five or ten hours a year, or even just one hour a year. But they will never quit. However the amount of flying they do may not be significant.
Here in Canada we have seen Avgas go up in cost by 50% in the last year, but unlike in the USA, it hasn't doubled in price. So I would expect that the results of a similar poll to this one, that just asked Canadian pilots, would not be so skewed towards the first response.
As gloomy as the results to that poll are, the second poll is much more positive, although we can examine how realistic the expectations are.
First off only 4% said they would never consider an electric aircraft. That means that 96% of pilots would switch to a battery-powered electric airplane to keep flying, or at least that they would consider switching. That is a result that reflects a lot of optimism.
The reason that AvWeb asked about battery-powered electric airplanes instead of fuel-cell-powered or hydrogen-burning or bio-fuel-burning aircraft is obvious, there are none of those aircraft flying right now and the difficulties of getting them flying outside a test environment are quite high. On the other hand battery-powered electric airplanes are here today, available commercially and they work. They are also quite cheap to fly, the "fuel cost" being under $1 per hour. Fuel cell aircraft (other than one Boeing test project) are still many years away and they will be expensive for the performance, if they are ever commercially available.
The most interesting results from the second poll are buried in the details. As noted in the last blog entry, you could buy or build an aircraft that matches the first response, today: "500 fpm, 60 kt, 200 lb (single seat), 2 hr", but only 2% would be happy with that kind of performance.
The largest response by far, at 38%, was for an aircraft with performance of "500 fpm, 120 kt, 400 lb (two-seat), 4 hr". That sounds like a battery powered CT-2 or something similar. The question is: "is that close to reality today, given the current state of the art?". Let's look at that.
The limiting factor in electric flight is the battery technology. ElectraFlyer uses lithium polymer batteries that can provide 5.6 kwh of power at a weight of 78 lbs, which is 13.9 lbs/kwh. To meet the performance goals stated, an aircraft like a CT-2 would need to produce 100 hp (75 kw) for 15 minutes and then 75 hp (56 kw) for 3.75 hours, for a total of 229 kwh, not counting any reserves. Using lithium polymer batteries this would mean that they would weigh 3180 lbs, a bit heavy for a CT-2-like aircraft, with a gross weight of 1320 lbs.
Of course lithium polymer batteries are just the best available today, not tomorrow. Right now the next generation of batteries with the best promise are probably hyper-capacitors. Instead of a big container of chemicals, these are banks of capacitors that can soak up a charge and then release it on demand to the engine. They have some real advantages over chemical batteries: they are lighter, nothing to spill and they can be recharged quickly, if you have enough amps and volts available to charge them fast.
One new state of the art hyper-capacitor is made by EEStor and will power the next generation Canadian-made CityZENN car. In the car application it will produce the power to let the car do 100 km/hr for 4 hours, which makes it a pretty practical electric car. The EEStor hyper-capacitor weighs 300 lbs and holds 52 kwh of power, which is a power density of 5.8 lbs/kwh. This is obviously twice as good as the lithium polymer battery.
With a hyper-capacitor our hypothetical CT-2-like aircraft could meet the mission requirements with a battery pack that weighs 1321 lbs. That happens to be the gross weight of the aircraft, but it is getting closer to reality. The current CT-2 engine and fuel weight for four hours is close to 310 lbs. Electric motors and controllers weigh considerably less than their gas-burning equivalent, so there is some savings there. Basically, though to have a practical "500 fpm, 120 kt, 400 lb (two-seat), 4 hr" airplane battery technology needs to produce a battery that will hold 229 kwh of power in a form that weighs around 260 lbs, for an energy density of 1.13 lb/kwh. This would be about 12 times better than lithium polymer or about 5 times better than the next generation of hyper-capacitors.
Can it be done? I sure hope so!
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It's an interesting discussion, both on the fuel cost side and the electric side.
In terms of fuel costs, it's still the lowest cost of owning and operating an aircraft. Also, with the fuel costs it's still cheaper to run my plane that it is to run my truck on similar trips. Granted I fly a very efficient plane (as 50 year old planes go) and drive a very large truck. There is probably a point at which I'll stop flying, but it'll be because to overall cost is too much or TC decides that I shouldn't be flying anymore.
In terms of electric, that option makes a big assumption, that buying a new plane is possible. To change planes I'd have to sell my current plane for probably a $30K loss and then be able to buy a new plane for five times as much. Isn't going to happen. The only real option would be to change the power plant on my existing airframe, but that's not too practical either. The only remote option that exists today is diesel, which is not STC'd for my plane (and never will be, there are too few of them around) and it would cost in the range of $60+K to have installed. I can buy a lot of Avgas for $60K, and I can buy even more for the $120K that is being talked about as the option for electric.
Another point is that I don't see much value in a plane that only has a 400Lb useful load. It might be fine for me to bash around the patch alone, but I'd never be able to take any but my smallest friends along for the ride.
You bring up an interesting point with your comment: "In terms of fuel costs, it's still the lowest cost of owning and operating an aircraft."
Everyone I talk to lately is talking about avgas costs, which in checking my records, were $1.35 per litre two years ago versus $1.75 today (at Carp). This is only a 23% increase, nothing like the 100% increase that US pilots have seen, due to the additive effects of their falling dollar.
I ran some numbers to compare the costs of operating two typical GA aircraft, a C-150 and SR22 between 2006 and 2008 to see what the difference in operating costs for a 100 hr year are.
In 2006 a C-150 would have typically cost $124.89 per hour, whereas today it would be $134.61, which is a change of only 7%.
In 2006 an SR22 which typically burns 17 US gph, would have cost $512.60 per hour, whereas today it would be $539.62, which is a change of only 5%.
In the case of the SR22 the fuel cost is currently (2008) $112.60 per hour which is just 20% of the cost of running the plane on a 100 hr year.
In the case of the SR22 avgas would have to get to $6.63 per litre to be half the running cost on a 100 hour year, provided other items (maintenance, parts, insurance) stayed at 2008 levels.
So you are quite right - it isn't the most expensive item here in 2008.
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