ul and lsa performance

[wyodan59]

Hello. I am trying to find performance information on ul's and lsa's. I live at 7000 feet in Wyoming. I learned to fly in a cessna 150 w/a 150 hp upgrade. This plane lifted off and climb out at 700fpm. at 11000 feet performance was very minimal. Doe's anyone have performance on low hp and high altitude? Will the Rotax 503 preform at my altitude? Thanks

[Dana]

Like any normally aspirated engine, a 503 will operate at reduced performance at altitude. How the aircraft it's powering will perform at altitude depends on the aircraft design and loading.

[rosiejerryrosie]

Best bet is to look at airports in your area. Any ultralights or LSAs flying there?

[wyodan59]

There are not any ul or lsa or ultralite aircraft near me. The smallest plane is a cessna 150. It sits on the ramp a lot. I guess what I am fishing for here is. Knowledge form someone that has some real world experience flying these small motors at altitude.

[Dana]

It's not just the motor. Altitude will have the exact same effect (proportionally) on a 503 as it will on the 0-200 in a C-150. Depending on the aircraft design. i.e. how much power is required, and how well it performs at sea level, it may or may not perform adequately at 7000'. One thing to look at is the service ceiling of the aircraft... the higher that is, the better it will perform at altitude.

[Bill Berson]

A pair of small electric motors could be fitted to any design to boost takeoff.
Electric has no loss at 7000 feet. The props would need to be a bit larger for optimization at 7000 feet.

[gotandem]

Dan wrote:
"I guess what I am fishing for here is. Knowledge form someone that has some real world experience flying these small motors at altitude."
We tow hang gliders to 10.000' with a 582 equipped Liteflight Dragonfly LSA every day in the summer. Our operation is at 5600 feet and 6200 feet in Jackson Hole, WY. So I guess I have the knowledge you're looking for.
Expect about 80% of the power that would be available at sea-level. It depends on your particular situation if that is enough for you.
Bart

[steveinindy]

There are not any ul or lsa or ultralite aircraft near me

That should be a big clue.

Knowledge form someone that has some real world experience flying these small motors at altitude.

We tow hang gliders to 10.000' with a 582 equipped Liteflight Dragonfly LSA every day in the summer. Our operation is at 5600 feet and 6200 feet in Jackson Hole, WY. So I guess I have the knowledge you're looking for.
Expect about 80% of the power that would be available at sea-level. It depends on your particular situation if that is enough for you.

But what is the density altitude running during those days? That's the big deciding factor. Personally, I wouldn't be comfortable trying to balance high altitude and low power but to each and to their own.

Electric has no loss at 7000 feet. The props would need to be a bit larger for optimization at 7000 feet.

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.

[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.