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wyodan59
12-04-2011, 02:07 PM
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
12-04-2011, 09:22 PM
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
12-05-2011, 10:56 AM
Best bet is to look at airports in your area. Any ultralights or LSAs flying there?

wyodan59
12-07-2011, 11:31 AM
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
12-07-2011, 01:19 PM
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
12-07-2011, 01:40 PM
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
12-11-2011, 10:39 AM
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
12-12-2011, 02:34 PM
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
12-12-2011, 04:49 PM
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
12-12-2011, 07:34 PM
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
12-12-2011, 10:10 PM
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
12-13-2011, 11:20 AM
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
12-13-2011, 01:07 PM
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
12-20-2011, 07:29 PM
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
12-21-2011, 02:22 AM
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.

Bill Berson
12-21-2011, 11:37 AM
Steve- electric motor technology is advanced. Current motors are very light and up to 95% efficient. Batteries are limiting technology.
That's why short boost with a small battery is better than trying to go pure electric. The range is limited on pure electric vehicles and the huge battery would cost too much for the limited battery life.

The Chevy Volt is a plug-in hybrid.
Read about this in the book: Car Guys vs. Bean Counters by Bob Lutz, 2011

steveinindy
12-21-2011, 07:54 PM
Steve- electric motor technology is advanced. Current motors are very light and up to 95% efficient. Batteries are limiting technology.
That's why short boost with a small battery is better than trying to go pure electric. The range is limited on pure electric vehicles and the huge battery would cost too much for the limited battery life.

To me, especially on aircraft where there is a definite upper weight limit by regulation, the idea of lugging around extra weight for an "extra boost" seems a bit odd. I was speaking about the battery weight issue not the motors themselves. If you have such marginal performance with a design that a second motor is a consideration, the design in terms of the primary engine, wing aerodynamics and drag needs to be reassessed. I am a big believer in the KISS method of aircraft design: the fewest systems and parts able to do the job means the fewest systems and parts to break and cause problems which is usually a very good thing. Put a bigger engine on the plane instead of trying to figure out how to have one you have to rely upon for takeoff and then shut down.

Think about it this way: what happens to your "hybrid" design if you need to go around in one of these high DA airports and you can't get the little motor started because of some mechanical issues that has gone unrecognized because it has been shut down until just before you need it? That would be my big concern. It's not just necessary to have it running for takeoff but for any activity that involves what would be more or less the standard performance of said aircraft. Simplicity of systems design in such situations is going to be your best bet. Adding 25-100 lbs of extra weight just to get the "gee whiz" factor of a marginally performing but technically advanced aircraft is simply an extra 25-100 lbs of extra mass to add to the F=ma equation that will likely determine the severity of your injuries in the event of a crash.

It's not like you have to be so concerned with fuel consumption in this class of aircraft that you need to move towards an hybrid system since even the high end of UL and LSA engines sip gas like a man missing his upper lip compared to your "average" GA engine. I would think developing a Rotax or something like that which doesn't freak the hell out if it comes in contact with ethanol would be a much more productive gambit. It's not that I don't think electric aircraft or hybrid aircraft are an inherently bad idea, I just think it has an almost Rube Goldberg-esque quality to it when it comes to solving a problem that can be solved much simpler and more effectively with better established technology for the same or, in some cases, less of a weight and drag penalty.


The Chevy Volt is a plug-in hybrid.
Read about this in the book: Car Guys vs. Bean Counters by Bob Lutz, 2011

Yeah, it works in cars because they don't have to be (as) concerned with weight as those of us in the aviation side of things have to be. You have a few extra pounds on the vehicle- even if poorly placed- it is highly unlikely to be an issue to anything beyond the life of the brakes and suspension.

Bill Berson
12-21-2011, 08:47 PM
Steve- I am suggesting that an electric boost system might be lighter than getting a larger Rotax for the brief power. Also, dividing the power between two sources, engine and electric booster gives the option of twin engine safety. The electric could allow for an extra minute of controlled flight after engine failure at takeoff. Burt Rutan suggested this at Osh last year.

The only reason I will wait a bit longer is battery cost. Cost should improve somewhat every year.

steveinindy
12-21-2011, 09:41 PM
Burt Rutan suggested this at Osh last year.

I recall him making an offhand comment during one of his presentations that I attended but based on the multiple times I have heard him speak, he seems to like to theorize out loud.



gives the option of twin engine safety

Are we talking driving this thing through the same propeller as the engine or are we talking about a second setup? I don't see a second engine as being an added positive aspect of safety unless it's properly designed and properly used by people who know what they are doing.


The electric could allow for an extra minute of controlled flight after engine failure at takeoff.
The question from an engineering standpoint is would the minimal added thrust you're counting on for "an extra minute of controlled flight" be sufficient to truly give that and would it be sufficient to actually counteract the added weight?


Cost should improve somewhat every year.

Given how much Fox News is crowing about the Volt and other electric vehicles, I think if the Republicans win we can kiss a lot of the federal funding that is driving the battery research goodbye shortly after the inauguration. It might not be directly affecting the electric aviation but I am willing to bet that the real progress in terms of this isn't coming out of the handful of guys working on electric or hybrid planes.


I am suggesting that an electric boost system might be lighter than getting a larger Rotax for the brief power.

Well, let's look at then the numbers:
Rotax 447 39.6 hp 61.3 lbs (with carb)
Rotax 503 45.6 hp 71.2 lbs " "
Rotax 582 64.4 hp 64.4 lbs "
Rotax 618 73.8 hp 76.5 lbs
Rotax 912 81.0 hp 127 lbs
Rotax 914 115.0 hp 137.1 lbs
(SOURCE:http://www.theultralightplace.com/installationweights.htm )

I don't think you're going to find an electric motor and battery system that would effectively double your horsepower for a weight gain of less than 15-20 lbs (assuming you went from a Rotax 447 to a Rotax 618 with their respective exhaust systems). This is especially the case when you start figuring in a drive mechanism to hook it into the engine's propeller (or the weight of adding in an entire new propeller, it's attachments, etc), the mountings for the motor and batteries, etc. Even figuring in an extra 2.1 gallons of gas to allow for equal flight time with a 447 and 618, it likely would at most break even in terms of power and weight benefit. In a situation like that, it's probably the safer bet to go with the relatively better proven technology of an internal combustion engine such as those currently in use on UL and LSAs.

Bill Berson
12-22-2011, 11:18 AM
I didn't say double, I said 25% boost. A motorglider type design might maintain altitude on 25% or at least extend glide.
Some are going all electric, some hybrid. It depends on the aircraft class.
Sounds like electric might not be for you. In the low power range (10-20 hp) electric is competitive, I think.

Dan Grunloh
12-22-2011, 12:00 PM
Those weight tables can be a bit misleading because of items not included. The installed weight of a Rotax 447 is 82 lbs with B-reduction drive, recoil starter and exhaust. The 618 will weigh 126 lbs with electric start (needed), and a heavier reduction drive (also needed). That total does not include the 25 lb battery to crank it, and the coolant! The difference in installed weight is close to 60 lbs. The 30 HP electric motor on Mark Beirle's Thundergull weighs 16 lbs. Most planes can cruise on half the engine needed to takeoff and climb. For the 618 you are carrying 60 lbs that you don't need for most of the flight. Jeron plans to run the same prop with both engines. You need a reduction drive anyway but will have to add a sprague clutch. Plenty of room in the cowling for the electric motor the new ones are tiny. Look at the Thundergull electric motor in the photo album for August 2011 Light Plane World. Hybrid designs may not replace ordinary aircraft real soon but you are going to see them flying pretty soon at airshows

http://www.eaa.org/lightplaneworld/issues/1108.html

steveinindy
12-22-2011, 11:07 PM
Hybrid designs may not replace ordinary aircraft real soon but you are going to see them flying pretty soon at airshows

I just think the added weight and complexity of trying to rig an electric motor into the propeller, etc is not worth the trouble.


you are going to see them flying pretty soon at airshows

Eh. I see a lot of things flying around and I don't necessarily give them anything but a passing glance. Whatever floats your boat my friend. All I ask is that you do whatever interests you in a safe and effective manner.


Most planes can cruise on half the engine needed to takeoff and climb.
Can they do it safely at the altitudes the guy who started this thread is talking about? Especially during high DA settings? I am simply looking at this as the most effective way to do it.


Jeron plans to run the same prop with both engines. You need a reduction drive anyway but will have to add a sprague clutch.

Like I said, I have questions of whether the supposed power loading benefit is outweighed by the risk of applying new technology and more complicated systems into a group of aircraft where construction and maintenance at times leave something to be desire. If the idea here is to make this as minimally difficult to build, operate and maintain so we can get more people flying as easily as possible, then adding complexity is not necessarily the best approach.

Ron Blum
12-23-2011, 11:57 AM
Although our original poster is probably gone, the couple bits of good information that he got were the people that did fly like he wants to and the fact that electric motors don't degrade with altitude (to a point).

Electric power storage is still too heavy. Electric motors are always lighter than gas engines; electric fuel is always heavier than gas fuel ~16:1 (but decreasing :o)

Burt has mentioned several times about flying an electric aerobatic routine. This is the most sensible (he knows the limitations). That would be high power for very short durations.

I am curious how a hybrid powerplant would be advantageous? Car and airplane power requirements are completely different. The car needs lots of high, varying power in town and little, continuous power on the interstate. An airplane needs high, continuous power all the time (except for the airshow routine).

I am also willing to take this conversation off the forum (since it is no longer the original post topic).

Always wanting to learn more ...

Thanks, Ron

Bill Berson
12-23-2011, 12:24 PM
Ron,
Electric has no advantage if your mission, as stated, is to fly on "high continuous power". The hybrid advantage is for folks that cruise at near best L/D.
In this case, additional power is required for climb. Since climb is short duration, a brief output from an electric system makes sense.
Really, the same as a hybrid car that uses electric to pass or climb a hill.

Electric has some "new" possible advantages such as increased flexibility in motor location, for example. And some disadvantages. Try to use the advantages and minimize the disadvantages.

Van (RV designer) has an electric motorglider. (I think Van knows what he is doing most of the time, and has a blog about this)
But Van doesn't have an electric airplane.

Electric has some niche applications.
Bill

steveinindy
12-23-2011, 07:24 PM
The hybrid advantage is for folks that cruise at near best L/D.

Which I don't think many ultralights do especially when you figure in high density altitude. Most of them are pretty draggy aircraft because of the very nature of the designs that are used. A pusher proper (the most common configuration I have seen in UL aircraft, at least around here) is already at a disadvantage because of operating in the disrupted wake. If memory serves, I think Ron's a trained aerospace engineer with a specialization in aerodynamics. He could probably discuss your argument in much greater detail than I could.


Electric has some niche applications.

It does. I don't think anyone is saying that it does not. The discussion is over what precisely those niches are and the technical limitations of the technology at the present happen to be. One of the big problems in experimental aviation is that folks latch onto what works in a carefully controlled setting (such as product development or under the guidance of the likes of Rutan or another great) and try to apply it to their own work without realizing that there are a few issues that don't tend to be as well publicized in such situations.

Ron Blum
12-24-2011, 10:06 AM
Bill, thanks for the thoughts.

There are so many people out there that think electric is the right way to go (which it may be, but we are not there yet with storage ... as you mentioned earlier). For an automobile the electric motor makes tons of sense: constant, high, low-end torque and zero fuel usage when stopped. Big city driving.

The torque curve for an airplane on the other hand is set by the propeller, a simple 2nd-order exponential curve (which actually mates to a gas engine fairly well). Successful electric airplanes (to date) have been very high altitude; very long winged; very, very, very low power applications. But still way cool.

Another thing that people do (like with automobile engines) is to use the rated horsepower ... continuously. One can do that in an airplane engine (it's certified to do that), but a "typical" 150 Hp automobile engine putting out 150 Hp continuously would exploxed in a matter of a few hours. Most of the larger electrci motors that I have looked at will run continuously at about 50% rated power. And, cooling is an issue ... ask Sikorsky on their Firefly.

We need to continue to ask questions and push the status quo ... lest nothing will ever get done.

Thanks,
Ron

Jon Ferguson
01-24-2012, 03:04 PM
I like the old answer best. They figured this out in WWII, just add a supercharger to force more air into the engine at high altitude, simple and effective.

Bill Berson
01-24-2012, 06:40 PM
Even simpler is to increase the compression ratio for a high altitude engine.
Then the engine must never be used at sea level with full throttle.
This was done in the old days.