ul and lsa performance

[Bill Berson]

But the excessive weight involved with even a small electric motor and the larger props necessary are likely going to make such an aircraft unfeasible. It's the same problem that keeps electric aircraft from being anything more than a sideshow attraction at Oshkosh no matter how much effort we pour into them.

Nope. I am suggesting a light electric boost system for takeoff only. For short burst takeoff of a few minutes, an electric motor and small battery is lighter than a similar gas engine (even two stroke) at sea level. And at 7000 feet the electric boost would have an additional weight advantage. Electric boost has the advantage of instant on when needed.
I watched an electric ultralight fly daily at Oshkosh 2011. It does work. But is expensive.
I am suggesting electric only for enough boost to replace the 25% power loss from takeoff at 7000 feet. Less cost than going 100% electric.
Bill

[steveinindy]

I watched an electric ultralight fly daily at Oshkosh 2011. It does work. But is expensive.

There's a big difference between puttering around the pattern at Oshkosh and trying to fly in the mountains. Also how precisely does an secondary electric motor save weight? You're going to have batteries, then the motor, then fuel then the real powerplant.....so once you shut the fan off, you're going to be packing around a bunch of extra weight you don't need. I mean, why not say 'screw it' and just go for the full out rocket assisted take-off? At least then you could ditch the extra weight once you're off the ground. LOL

I am suggesting electric only for enough boost to replace the 25% power loss from takeoff at 7000 feet. Less cost than going 100% electric.

So what about the problem of cruise at 7,000 AGL (or in the case of the summer time out west, 9,000 AGL or more once you figure in DA changes) with an under-powered engine? I don't think strapping a secondary motor to the problem is the issue. Just going with a bigger engine to start with would probably be the best course of action (short of staying on the ground if all you have is an LSA or UL in situations like that). Sometimes, throwing new technology at a problem may "solve" the issue at hand (sort of in this case) but simply shifts that risks to another area. A more or less unproven technology (and a few random examples of electric aircraft flying for demonstration purposes isn't really proof that it can be broadly applied yet) used to fix a problem that can and does kill people sounds like a less than ideal solution.

Maybe in another 15-20 years we will see practical application of the electric aircraft concept. I fear that it will also depend heavily on which way the next election goes.

[S3flyer]

Back to the original question, I have to agree with Dana that it depends on the specific aircraft design. I'm not personally aware of 503 powered planes at higher altitude airports but do know of many 912ULS powered LSAs based at elevations up to 7500 feet. My particular LSA has a service ceiling above most 180hp fixed gear GA aircraft (16000 ft).

[Bill Berson]

Steve,
At sea level, most pilots takeoff at 100% and cruise at 75% power. But 75% is all you get at 7000-8000 feet and that is enough for cruise. If you want to cruise at 100% power than get the bigger engine.
Electric boost is an option now. Not just my idea, Burt Rutan suggested the same last year. Of course it is experimental.

[Bill Berson]

Back to the original question:
High altitude limits the performance. The solution is usually to reduce the gross weight. Floatplanes are forced to fly with reduced payload. For example, a Cessna 172 on wheels is a four seat airplane, but on floats is usually limited to two seats to get off the water.

High altitude flight conditions is a bit different than float plane issues, of course, but buying a four seater and using it as a two-seater might work. Or a two-seater flown as a one-seater... or use a loooong runway.
Bill

[Dan Grunloh]

WyoDan you said 700fpm was minimal in 150. You probably also talking about climb angle. For an ultralight or trike, 700fpm at that altitude would be plenty. It would need to do at least 1300 (or probably more) at seal level. Simply pick a craft like an STOL that does 1300+ fpm at seal level loaded the you want to load it.

And by the way, Bill is ahead of his time but only a little.

Hybrid gas/electrics are coming soon and maybe sooner than pure electrics. You should hear Jeron Smith (Raven redrives) talk about it. Probably building right now. Electric and gas for takeoff and climb but then gas only for cruise. Batteries much smaller. Better range. Engine charges batteries in flight.

[steveinindy]

And by the way, Bill is ahead of his time but only a little.

Hybrid gas/electrics are coming soon and maybe sooner than pure electrics. You should hear Jeron Smith (Raven redrives) talk about it. Probably building right now. Electric and gas for takeoff and climb but then gas only for cruise. Batteries much smaller. Better range. Engine charges batteries in flight.

I still think you guys are being overly optimistic about how fast the electric motor technology is going to advance. Of course, it also might just be a difference in what you all seem to consider useful and what I consider to be so.