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Altitude and turbines

Old 08-03-2008, 08:39 PM
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seflyer
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Default Altitude and turbines

i have access to a 7400x150 paved runway at 2600 foot elevation, how much thrust loss would i experience versus the 500 ft I usually fly at or would I have to worry about it? I need to test fly my new f-86 and want all the runway i can get. What altitude do most of you fly at? thanks Kevin
Old 08-03-2008, 09:04 PM
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Default RE: Altitude and turbines

Flying at 3000 feet ASL all my modeling career. The only noticeable problem in turbines here is that some of them gurgle or flameout if the acceleration rate is set too quick.. the smaller ones the worst. Besides that, the turbines seem to keep the same thrust as at sea level, and the planes fly faster too. The downside is that stall speeds are slightly higher
and the controls feel sligthly less crisp.

Enrique
Old 08-04-2008, 05:51 AM
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Default RE: Altitude and turbines

Altitude and heat are not friendly elements for turbines. I fly at 4000 ft and during summer time (hot days) i am having exactly what you are discribing. I thought first that there was a problem with my 36 lbs turbine, but when tried under different conditions, all went well.

Flying wise, not much difference between sea level and this altitude....

Regards.
Old 08-04-2008, 06:38 AM
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Default RE: Altitude and turbines

we have the same problem, in our city the altitude is 900 ft, but the temperature is very hight in summer, and, we have other problem, the barometric pressure, that varies as the altitude, minor the turbine, greater is the effect.

hope help [8D]

jose
Old 08-04-2008, 06:39 AM
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Default RE: Altitude and turbines

in time !!
how much better the management of the ECU, minor the risk of imperfection of the engine

jose [8D]
Old 08-04-2008, 07:12 AM
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Default RE: Altitude and turbines

Applying standard correction factors for air density, the rule of thumb is about 3% per 1000 ft. of elevation. So if everything else is equal you can expect about a 6% thrust loss at 2600 ft. versus 500 ft.

Joe
Old 08-04-2008, 08:31 AM
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Default RE: Altitude and turbines

Interesting question. Some good points on this thread.

Since, I only fly at, or around, sea level I can't add much, but I'm sure learing!

I bet your maiden will go great. The F-86 is an absolute marvel to fly.

Raf
Old 08-04-2008, 09:02 AM
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Default RE: Altitude and turbines

Altitude is definitely something we have to contend with in Albuquerque (alt 5800 ft). There is definitely a reduction in thrust and in lift. This makes takeoff runs longer and landing speeds higher. The top end speed doesn't seem to be effected. Landing can be a bit more of a challenge as you really need to bring the bird in as slow as possible. Speedbrakes or a high drag airframe or big flaps are very handy.

Turbines operate a bit differently at that altitute; most folks fly Jetcats which have been set up internally for high altitude. My old RAM750 uses compressor pressure (rather than RPM) for speed control and has to be derated to prevent an overspeed since at a given RPM, less compressor pressure is produced.
Old 08-04-2008, 09:11 AM
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Default RE: Altitude and turbines

And that same 3% decrease in performance for every 10F temp increase, as well....this relative to a Standard day (sea level, 59F).

You can see, then, that at 3000 above sea level, and say 90F OAT, your losing about 18% of the thrust the manufacturer specified/tested on a standard day. Similar loss of lift for the model too....yer gonna need a looong runway.....

Ray
Old 08-04-2008, 09:23 AM
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Default RE: Altitude and turbines

Ok, thanks for the input. i guess i'll put a few flights on my f-16 first as i have become comfortable with it and then fly the f86. hope all goes well. Raf, hows the chippy ho? I missed LA Jets[] looks like you guys had a blast. Kevin


long runway I got, it is listed at 7400 officially but on google earth with the paved end beyond the markings it is about 9200ft. it is located in Montague CA north of Mt Shasta so it even further north than me here in redding. there are no trees in site.
Old 08-04-2008, 09:40 AM
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Default RE: Altitude and turbines

I'm in the middle of converting to 2.4. Ouch (that was my wallet by the way! ) The chippy is going to get some serious flights in coming right up!

We missed ya down in LA man!

Raf
Old 08-04-2008, 10:39 AM
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Default RE: Altitude and turbines

Kinda bummed I didn't make it either, its a heck of a drive from Redding, the willow was 537 miles but I stayed four days. I have a pile of new ar 9000 receivers though, I know the wallet hurting thing to well. I made the switch last year but we took full advantage of the buy/get one free. Now I have to suck up the purchase of the 12x, I guess I'll get over it though. still waiting on Darcy for my flash quote so I can join the hill climbers next year at the Willow[sm=thumbs_up.gif]

after flying the 86 I'm going to built the shockjet that is due to arrive thursday and then get the flash. sometime next year I will get the hornet. Kevin
Old 08-04-2008, 11:14 AM
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Default RE: Altitude and turbines

ORIGINAL: josecilurzo

we have the same problem, in our city the altitude is 900 ft, but the temperature is very hight in summer, and, we have other problem, the barometric pressure, that varies as the altitude, minor the turbine, greater is the effect.

hope help [8D]

jose
Yes, barometric pressure, temperature and humidity also affects the minimun ramp up/down times in turbines, specially the smaller ones.. Fortunately for us, temps and humidity are usually lower than average for our country. Nothing is better than a winter cold day, (about 10 celsius) with a cristal clear blue sky for enjoying some turbine flying.

Seflyier: don´t be worried about the takeoff at all.. a real jet killer while flying in this adverse conditions (altitude,temperature, etc..) is that dreadful last turn at landing. Keep it smooth (low g) avoiding a premature stall wich have taken out of the skies so
many jets.




Enrique
Old 08-04-2008, 11:26 AM
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Default RE: Altitude and turbines

erbroens, thanks for the input, I will be very careful on the maiden and watch me speeds, especially on baseleg and final turns. I have chosen this field for the maiden as it is totally unobstructed by any obstacles and with 7-9000 feet of runway landing should be a non issue, I always hated test flying something when there obstacles like trees or fences that had to be flown around. my first flight will involve very wide low bank angle turns until i get the feel for how it flys and I can turn final way out there and let it settle with no worries about running off the end of the runway. I've see raf's video of his maiden at the tomcats field and that is tight and fairly short so I should be ok. Kevin
Old 08-04-2008, 12:04 PM
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Default RE: Altitude and turbines

É isso ai Enrique!!

we have nice conditions in all country!!!
if it will be possible to operate an airplane with more thrust, we will have minor variation of flight conditions.

abrazos

jose
Old 08-06-2008, 03:02 AM
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Default RE: Altitude and turbines

We fly here at around 5000ft ASV all the time. As stated previously, loss of power is one effect and the loss of lift is the other. You might need to up the idle a 1000 or 2. Some of the turbines required that the "Ramp down" time be extended slightly. Good thing is that they still work at these altitudes!

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