JakeInHartsel

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I live up in the Mountains of Colorado. My planned flying site is at 9,600 feet MSL. Has anyone had any expereince flying at similar altitudes? I understand that engine power will be reduced and I was wondering if any one might have some tips engines, types of planes sizes, etc.

Thanks

Wyohi

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Laramie Wyoming not as high 7250ft. We usually go up 1 size in engine size don't fly 049 or similar. Gliders fly ok but do better in the flat lands. The larger the plane is it seems the change is less. WE fly most everthing that is out there. I am working on electrics since the new motors came out & am having good luck. Got a 40 size trainer on electric which does as good as power. Of course it was a lot more expensive but is a ball to fly & no goopy clean up.

Joe Ortiz

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I was wondering about the same thing, I live in Aurora CO, is there any engine tunning tips for high altitude?

Homebrewer

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Engine tuning is the same whether you are at sea level or at 10k feet. Tune for max rpm and then back off by about 300 rpm.

I flew a little in Colorado Springs last month and I used 20% nitro fuelin my Royal .46 engine with no problem. The extra nitro seemed to allow it to run at the same rpms it runs back home in Iowa (flat lands) on 10%. You can get away with higher nitro at higher altitudes without fear of detonation.

den1tjb

Like homebrewer said, just tune it like you would at a lower altitude. I have been flying here in littleton, CO for close to 8 years now. During the hot days in July, it can sometimes feel like you are fighting to keep the plane in the air compared to cooler days in winter/spring.
My advice...tune the engine, point it into the wind, and have a ball. If it is the only thing you have ever known, you will not know the difference.

redrocker

I fly at about 4000 feet and the combination of altitude and summer heat can combine to zap you because you are losing both engine power and lift. I do lots of scratch building so I just basically over power the plane, and provide generous wing area for the weight. It works.

TexasAirBoss

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I live in Texas now and our field is about 200 feet above sea level. I grew up in Eastern Tennessee and flew models there at about 2000 msl, some fields were close to 3000 msl. I know I don't run 15 % nitro in Texas. It just doesn't seem to do much. But in the mountains there seemed to be a big difference between 10% and 15%. I guess that makes sense really, you want to burn as many of those spaced out O2 molecules as you can in the time available. I believe that the nitro is really just a long chain molecule with an oxygen on the end that is easily knocked off and reacted . I think it is more of an oxidizer than a catalyst.
I do remember that on really hot summer days, one of my models would simply not take off on the 240 feet of hard runway available. I do believe that density altitude does vary much more in the mountains.
Short answer: I would suggest 5% more nitro.

vtol_guy

or you could get a YS engine, they have superchargers on them therefore getting rid of your engine problems at high altittudes

xlr82v2

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Nope, supercharged engines are affected by altitude just as naturally aspirated engines.

What you need is a Turbocharger. Turbos are not connected to the crankshaft, so they are free to spin as fast as necessary to produce the required level of boost, up to the critical altitude of the turbo (critical altitude is the altitude where the turbo can no longer maintain sea level power).

A Supercharger is different in that it is driven by the rotation of the crank, so the level of boost is directly related to engine RPM. Therefore, on every intake stroke, the supercharger takes in it's gulp of air, compresses it by whatever boost factor the supercharger is rated at, and delivers it to the cylinder. The Supercharger cannot compress the air more than this, unless you change the gear ratio to spin the SC faster. Generally not possible in flight. So, as you increase altitude, the SC is getting less and less atmospheric pressure pushing air into it, and since it can't spin faster to compensate for the loss of atmospheric pressure, your power output drops just as it does for a normally aspirated engine.

This is why the Merlin engine in the P51 mustang had the 2 speed supercharger... Low speed for low altitudes and high speed for high altitudes.


I hope this is a little clearer than mud...

JakeInHartsel

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Thanks Brian, I have learned something new and that makes today a good day.

vtol_guy

actually, technically turbo chargers are affected by throttle control just like superchargers are, turbochargers are powered by the exhaust, now, im not a genious with engines or anything but on idle i dont see a great lot of exhaust fumes on idle, i see them when they are at full.

i dont know for certain but i was taught that if air is compressed before going into the carb at ground level, more power can be gained, so if you have compressed air at a higher altitude then it will be more like the air pressure at ground level rather than 9000ft or wotever

Sorry, im no genious on the subject, that is what i was taught about it and that is what i think is correct, i aplogise if this is wrong

xlr82v2

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vtol_guy,

Yep, you're right. But who flies at idle?

And you're also right in that if you compress (via Supercharger or Turbocharger) the intake charge, you pack more oxygen molecules into the cylinder. Therefore you can burn more fuel, and, presto!... More POWER.

What I'm saying is that a Supercharged engine will lose power as altitude increases just as a naturally aspirated engine does. A turbocharged engine does not have this handicap, until critical altitude is reached. Above critical altitude, the turbo'ed engine will lose power with increasing altitude just as the naturally aspirated and the supercharged engine will.

Look at it this way:

Let's say we have 3 theoretical engines, of 1.0 cubic inch displacement. One is naturally aspirated, one is Supercharged, and one is Turbocharged.

At Sea Level, the naturally aspirated engine will produce 2.5 horsepower, the supercharged engine will produce 3 horsepower, and the turbocharged engine will produce 3 horsepower also.

Now, let's take the engines up to 10,000 feet.

Naturally aspirated engines can only produce about 60% of their rated power at this altitude, so it is now producing 1.5 horsepower.

The supercharged engine, since it suffers from the same altitude effects as the naturally aspirated engine (due to the inability to increase the rpm of the supercharger to compensate for decreasing atmospheric pressure), will be down to 1.8 horsepower.

But the turbocharged engine, since it is not affected by altitude since the turbo can spin faster to compensate for the decreasing atmospheric pressure, will continue to produce its Sea Level power rating of 3 horsepower. It will continue to produce 3 hp until the altitude is reached where the turbo can no longer spin fast enough to compress the ambient atmospheric pressure air to sea level pressure. This is called Critical Altitude. Above this, the turbocharged engine will lose power with increasing altitude just as the NA engine and the SC engine.

So what does all this mean?

Getting back to the original statement that a YS would solve the problems of altitude since it is supercharged is not totally correct. Yes, it will produce more power than a normally aspirated of the same size, but it will still suffer the same altitude effects as the non-YS engine. To get the engine to produce the same power at 9600 feet as it would at sea level would require that the engine be Turbocharged. Not really practical with model engines.


But, wouldn't it be cool?

vtol_guy

it suddenly becomes very clear now

cheers!

Cyclic Hardover

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I am in Albuquerque (5000). There is roughly a 17% or 3%per1000ft power loss. Most of us who have been flying a few years overpower our planes. Now I severely overpower mine.
* To be safe use the highest recommended engine for decent performance. Got a .60-.90 size plane. Put a .90 in it. Sport engines do not seem to swift here. if we have a .40 size plane. put a 46fx or similar, not an "LA."
You will also lose a bunch of airspeed. My F-20 with a Jett .50 gets 125 mph here and that is great but down a sea level, these guys with the same setup are around 145-150.

dcknowles

I bought my engine used on eBay, a Saito .72. I can get it to start and run for about 5 seconds after I prime it, and I've done this several times.

The previous owner flew it about 25 times with no problems in Indiana. I'm in Utah along the Wasatch Front at about 4200 feet. Will I need to adjust the idle needle to get it to run here? Does altitude make a difference? Thanks.

JakeInHartsel

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Your altitude is similar to Denver and in Denver you would need to adjust both the idle and the fast settings. Although since it runs a little after priming it sounds like you might be too lean now. You may have to play with it a while, before you get it right.

P-51B

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I was out there for a while on a project (flew at the modelport and out by Grantsville), and noticed the difference due to altitude. You will likely have to adjust both.

smokingcrater

hehe, i fly between 1k and 2k in alt, and still do that!

LoboFlyer

slightly OT, but you also might want to slather on a little more sunscreen too since there is that much less atmosphere between you and the sun.

rrh

Jakeinhartsel,

It's been a while since your original post, how goes the flying at altitude? I live, and fly, in Colorado Springs, about 6000'. Quite often, during the summer, I drive right thru your mini-metropolis to visit and fly with my Dad up Poncha Pass out of Salida. Our altimeters tell us we are about 8700' there. The more I fly, the more difference I can notice between the 3000' difference. I don't have a problem getting the engines to tach out just lean em out, but the thin air seems to affect the wing design more than the engines. My combat ships do pretty good up there, I have a monster trainer type with a 72"x16" flat bottom wing and a FA100 Saito that works great. As has been said, mucho horsepower and a lot of hi-lift wing seem to be key. I have a couple of SPAD QHORs that fly wonderfully in the Springs but are a total struggle to keep in the air up Poncha. I am no aeronautics expert or anything but these are some observations we have made. I have yet to fly below a mile hi and look forward to it some time. Can't you find a place to fly out there in the flats of South Park? I would think that's a few feet lower than 9600'. I'm gonna try a over powered bipe next for hi-altitude stuff. The pine trees always win, an aspen grove makes for a pretty soft landing!

rh

JakeInHartsel

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rh,

Thanks for the reply and the Info. Actually the altitude is about the same. My house is at 9,700 and the place that I fly is about 100 feet lower. I live about 15 miles from the town(?) of Harsel about 8 miles off of 24. The only flying I have been doing is slow fliers and I have yet to grade a runway. New house and getting settled is taking too much of my time. I doubt I will do any serious flying before next spring, although if I can get the runway in maybe this winter.

If you would like to drop by one day on the way to your dad's drop me and email and I will give you directions.

Jake

dcknowles

I got my Saito .72 up and running tonight. It was the low end needle setting--it was too lean. It was apparently just right for Indiana, but at a higher altitude in Utah, I had to richen it up.

Thanks for your help, everybody!