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Question on high altitude flight (Read 252 times)

May 7^th, 2003 at 3:56pm

Paz Offline
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USA

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Posts: 1922

Alright, I do okay most of the time (those of you who have read my misadventures may disagree) but I'm having a little problem that I don't understand, I'm currently heading from Beijing down to Hangzhou to check out the new kick-ass airport scenery.
I'm flying a Learjet which is documented to have a ceiling of 45,000 ft or so and a top speed of 580 or something close to that. I want to get to Hangzhou and back to Beijing in a hurry because I still have business to take care of in the north. I figured the Lear would be the perfect choice.
I set my flight plan for FL410, now the problem is, I'm at that altitude, which wasn't easy to reach in the first place because my IAS wanted to stay around 170 at a climb rate of only 500 FPM after getting to the higher elevations, my climb started out great, around 1500 FPM at 300+ IAS, and now that I'm there, my speed still won't increase, I'm only moving at about 320 knots ground speed, and the plane is wobbling all over the place.
My gear is up, my flaps are up, I'm at straight and level flight, I can't see anything that would be causing excess drag, I should be hauling ass in the little lear-rocket.
Did I miss something??
What's going on??

&&Still no linked images allowed around here Paz! Naughty...&&

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Reply #1 - May 7^th, 2003 at 4:42pm

fisharno Offline
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Wow, Paz. I've never heard of the Lear doing that...

I wonder if switching to True Airspeed, instead of Indicated Airspeed would change anything?

Go to the settings and I think it's under the Aircraft tab.

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Reply #2 - May 7^th, 2003 at 6:05pm

MattNW Offline
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Indiana

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At high altitudes the air is thinner so the speed shown on your airspeed indicator will be lower than the actual speed of the plane. Airspeed is measured by reading the pressure created in the pitot tube and thinner air won't exert the same pressure as thick air. Check your true airspeed like fisharno suggested or look at the AP to see what percent Mach you are going.

In Memory of John Consterdine (FS Tipster)1962-2003

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Reply #3 - May 8^th, 2003 at 11:36am

Sky_Shark Offline
Colonel
Alway get under 200 ft...
dont waste ammo.

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Yes, while IAS will remain low, you should read your Mach Speed indicator.
But 320 knots ground speed is low indeed.
If the plane is acting strange, than I guess you should take into acount the weather. Temperature and particulary Atmospheric pressure determine the ideal cruising altitude. 40 000 ft is for standard condicions. Low atmospheric pressure requires lower altitudes.
maybe it's the wind or turbulence...

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Reply #4 - May 9^th, 2003 at 4:15am

757junkie Offline
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Perhaps icing could have something to do with this... Does the plane still misbehave if you change the realism settings?

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Reply #5 - May 9^th, 2003 at 4:56am

ZK-111 Offline
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Eat My Contrails

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Is it possible that you are too heavy with fuel. In the thin air up there you would stuggle to maintain alt and speed on full tanks. Just a thought.

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Reply #6 - May 9^th, 2003 at 6:20am

Ivan Offline
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i got to 45000-48000 ft with the lear, with quite a big fuel load.

and if you want to go somewhere fast, take a S-21, (there is a crappy FS98 one in the library it think) that one can do M2 at high altitude

Russian planes: IL-76 (all standard length ones), Tu-154 and Il-62, Tu-134 and An-24RV&&&&AI flightplans and repaints can be found here

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Reply #7 - May 9^th, 2003 at 7:05am

packercolinl Offline
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Any more laid back I'd
be asleep!

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I can't quite remember but go back through you flight setup,trim etc. I imagine you are showing nose up so look at your trim options. Cheers

White on White fly all night.&&&&Red on White you're alright.&&&&Red on Red you'll soon be dead.

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Reply #8 - May 9^th, 2003 at 5:19pm

snake Offline
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On your Six!

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First of all, why were you that high in a lear?

At that altitude a bunch of things happen all related to the lack of AIR.

1: There is so little air that your engines dont have enough to make sufficient power to push you any faster than that despite the apparent drag reduction you get by the lack of air.

2: there is so little AIR that your wings dont have enough AIR flowing over them to create lift. For an example, try flying at 25000 feet at 170 knots and see what happens, 10:1 it will be the same thing.

3: The service ceiling may say 48000 or whatever, But that is only a measure of what is possible, not recommended. For any practical purpose that is way too high for a lear. 30000 to 34000 should be just fine depending on weather. And to be honest I have found that I get better speeds at 31000 - 32000 feet.

This was happening because you were on the verge of STALLING, not flying. Come down a bit and enjoy the speed and live to tell about it.

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