AR1300
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High Altitude Cruising

Wed May 18, 2005 5:10 pm

I recently flew WN to and from Chicago,and on the way there we cruised at 41,000 feet.And on the way back we cruised at 43,000(!!!!)feet.Why is so?I never cruised that high before.Usually the higher that gets is 37,000 or so.It this a WN only thing? or other airlines cruise very high like that?

mike
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TimRees
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RE: High Altitude Cruising

Wed May 18, 2005 9:01 pm

Don't think it's that uncommon. I've often noticed flights I've taken across the atlantic climbing to 40K+ in the latter part of the flight as they get lighter on fuel. Sometimes in Europe too.

Certainly isn't a 'WN only thing'
 
miaskies
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RE: High Altitude Cruising

Wed May 18, 2005 9:06 pm

Quoting TimRees (Reply 1):
Don't think it's that uncommon.

I agree 100% ...

I have "cruised" at 39,000ft on AA 752 enroute from LGA to MIA., at 40,000ft on AA 763ER enroute from MIA to CDG over the North Atlantic Crossing into European waters...

Just recently in February, I flew AA 752 at 39,000ft enroute from SFO to MIA ..redeye.
Nothing better than making love at 35K Feet!
 
pilotaydin
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RE: High Altitude Cruising

Wed May 18, 2005 9:10 pm

I thought the max for 737NGs were 41K? am i wrong?
The only time there is too much fuel onboard, is when you're on fire!
 
EMBTucano
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RE: High Altitude Cruising

Wed May 18, 2005 11:37 pm

I am sure it is not uncommon to fly at this altitude.
Once I flew WN at FL410 from HOU to HRL which is a very short flight. I think we stayed at this level for less than 5 minutes.


Cheers
EMBTucano
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SimProgrammer
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RE: High Altitude Cruising

Wed May 18, 2005 11:41 pm

I did a ZRH LGW with easyjet in summer of 2003 - a 1 hour 15 min flight and it was at 42,000FT, a 737 700.

Quite strange for just a short flight, we were at cruise for less then 20 minutes - so it seemed...
Drive a bus, an Airbus, easier than a London bus!
 
roseflyer
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RE: High Altitude Cruising

Wed May 18, 2005 11:47 pm

The 73G max certificated altitude is 41,000ft, which means that there is very little chance that you went up to 43,000ft. Going up to 41,000 can be common, but you hit some major restrictions when going above there. Most commercial planes are not certified above 41,000. You usually only see business jets and military traffic up there. A number of people here on Anet though have said that they have been higher than 41,000ft on a 73G, which just confuses me.
If you have never designed an airplane part before, let the real designers do the work!
 
CosmicCruiser
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RE: High Altitude Cruising

Wed May 18, 2005 11:59 pm

Quoting RoseFlyer (Reply 6):
Most commercial planes are not certified above 41,000.

The MD-11 is certified to 43,200 ft. This gives it a legal max. of FL 430. You rarely see 410 because of weight and/or wind restrictions.
 
pilotaydin
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RE: High Altitude Cruising

Thu May 19, 2005 12:55 am

yeah i thought it was 41K now im pretty sure that's what i researched just now, because the max altitude is mostly decided by the differential pressure that the fuselage is designed to withstand..... so going higher than normal isnt an issue of thrust so much as it is Delta P
The only time there is too much fuel onboard, is when you're on fire!
 
Goldenshield
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RE: High Altitude Cruising

Thu May 19, 2005 1:51 am

In some latitudes, max altitude is also dependant on ozone concentration.
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Lemmy
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RE: High Altitude Cruising

Thu May 19, 2005 2:23 am

If an airplane is certified to fly up to fl410, will it actually fly at fl410? I ask because, if the plane unintentionally flies just a little bit higher (not likely with RVSM equipment, I know), it'll be technically above its max operating ceiling.

Or is this just silly?
I am a patient boy ...
 
prebennorholm
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RE: High Altitude Cruising

Thu May 19, 2005 5:25 am

Quoting Lemmy (Reply 10):
If an airplane is certified to fly up to fl410, will it actually fly at fl410? I ask because, if the plane unintentionally flies just a little bit higher (not likely with RVSM equipment, I know), it'll be technically above its max operating ceiling.

Dear Lemmy, there is no technical problem going higher than max certified altitude. The only thing will be that the automatic cabin pressure control cannot keep an 8000 feet pressure altitude any longer. That's a comfort problem, and for some ill passengers a health problem. And of course a legal issue.

Fully loaded most planes cannot reach their max certified ceiling. But lightly loaded (most fuel burned and low payload) most planes could climb considerably higher than max certified ceiling. The latter would be done on test flights only, and with test crews wearing oxygen masks.
Always keep your number of landings equal to your number of take-offs
 
Matt72033
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RE: High Altitude Cruising

Thu May 19, 2005 5:39 am

do engines not suffer a loss of efficiency above 36k feet as they enter the tropopause, where the Temperature remains constant, -57 degrees IIRC, and the static air pressure continues to drop! thus reducing EPR?
 
prebennorholm
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RE: High Altitude Cruising

Thu May 19, 2005 6:40 am

Quoting Matt72033 (Reply 12):
do engines not suffer a loss of efficiency above 36k feet as they enter the tropopause, where the Temperature remains constant, -57 degrees IIRC, and the static air pressure continues to drop! thus reducing EPR?

The engines "suffer" from every foot above sea level.

At for instance FL350 max engine thrust on a typical high bypass turbofan engine will be reduced to 25 - 30% of sea level thrust.

But then typical airliners have 5 - 6 - 7 times more thrust at sea level than what is needed for level flight. At low weight up to 10 times more than needed.

The available thrust on a Lockheed U-2 cruising at it's max altitude is only 5% of max sea level thrust.
Always keep your number of landings equal to your number of take-offs
 
CosmicCruiser
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RE: High Altitude Cruising

Thu May 19, 2005 7:08 am

Quoting Prebennorholm (Reply 11):
But lightly loaded (most fuel burned and low payload) most planes could climb considerably higher than max certified ceiling

That's a fairly big statement "considerably higher" and I'm not sure I'd believe that. I've never seen a jet perform very well at or near the max alt. at "legal" wgts. That's why it has a "certified max alt." In my first post I stated the MD-11 max as 43,200 'cause it can go to fl430 with a legal buffer. There's alot more to the max alt than just pressurization issues. I'm sure you're familiar with "coffin corner" in some older jets and many years ago an old ground school instructor who was teaching performance for the DA-20 told us "if you can't do 500 fpm in the climb you don't need to go there". He was a lucky guy who stalled a jet commander trying to climb over a TRW, fell into the storm and lived to tell about.


[
 
Lemmy
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RE: High Altitude Cruising

Thu May 19, 2005 7:23 am

Quoting Prebennorholm (Reply 11):
Dear Lemmy, there is no technical problem going higher than max certified altitude.

I was actually thinking more about the regulatory implications of flying above max certified altitude. Different scenario: What if you somehow wind up above this altitude (by accident, TCAS advisory, etc.)? Is there paperwork involved? Inspections? Flogging?

Can ATC or TCAS ever send you above your max certified altitude and, if they do, are you ever compelled to go there?
I am a patient boy ...
 
OPNLguy
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RE: High Altitude Cruising

Thu May 19, 2005 7:41 am

Quoting Ar1300 (Thread starter):
I recently flew WN to and from Chicago,and on the way there we cruised at 41,000 feet.And on the way back we cruised at 43,000(!!!!)feet

Max is FL410, and I suspect he either mis-spoke or you (with all due respect) mis-heard. We don't plan them above FL410, nor do we file them above FL410, and it makes no sense to be there.

Quoting Lemmy (Reply 15):
I was actually thinking more about the regulatory implications of flying above max certified altitude.

An aircraft's max altitude is an AFM limitation, and between regs that say "thou shalt comply with AFM limitations" and "thou shalt comply with company policy/flight ops manual/etc." one could get nailed for busting those regs as well as the catch-all "careless and reckless" reg...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
prebennorholm
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RE: High Altitude Cruising

Thu May 19, 2005 8:09 am

Quoting CosmicCruiser (Reply 14):
"if you can't do 500 fpm in the climb you don't need to go there".

A very good rule. Unable to do 500 fpm, then you have no business going there. For many airliners, for instance a heavily loaded B727, that may happen well BELOW max certified ceiling.

About coffin corner: Airliners do not operate anywhere near coffin corner. I think that I read here at a.net that there are very simple rules about that. Something like, whatever your actual weight you shall never go higher than you can make a +0.5 G vertical acceleration - meaning a 1.5 G dive recovery. Can somebody confirm or clarify that? Without such a substantial margin to coffin corner, then you could do nothing, even in the smoothest air, in case of a TCAS advisory telling you to climb.

And Lemmy, sure it is a legal issue. I'm only an "armchair pilot" but I assume that any major deviation from cleared FL will create a lot of paperwork.

But jumping 500 or 1000 ft above max ceiling caused by a TCAS advisory will physically be a non-event. The pax will briefly experience a cabin pressure dropping slightly below the comfort of 8000 ft. That's all.

What I wanted to point out was only that there is a wide difference between what a heavily loaded and a lightly loaded airliner can physically do. A long range plane with no payload and almost empty tanks is only roughly half the weight of the same plane at MTOW. But still it has the same wing area and engine thrust.
Always keep your number of landings equal to your number of take-offs
 
PhilSquares
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RE: High Altitude Cruising

Thu May 19, 2005 8:31 am

Just a few words from a cockpit perspective.

On the 744, the certificated ceiling is 45100. That is based not on the pressure differential, but the ability of the aircraft to descent to 14000 feet in 4 minutes or less. The aircraft is capable of higher altitudes at lower weights but you'd be a fool to do that.

Secondly, exceeding the certificated altitude is a BIG deal. You just don't do it. End of story.

At max TOW, the 400 will make FL310-320 as the optimum altitude. The max altitude is higher, but you will burn more fuel climbing above the optimum. The max altitude at those weights is determined by a 1.4 or 1.3 G buffet margin. Each airline can pick what it wants.

Hopefully, all that will help.
Fly fast, live slow
 
AR1300
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RE: High Altitude Cruising

Thu May 19, 2005 8:53 am

Coud be I misunderstund(sp) something.I was spacing out out when the captain started to pull those WN kinda jokes when said something about cruising at 40 ish k feet.I understood 43, so you could be right.
But the first one I actually heard 41 K.

Mike
You are now free to move about the cabin
 
CosmicCruiser
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RE: High Altitude Cruising

Thu May 19, 2005 9:29 am

Quoting Prebennorholm (Reply 17):
Airliners do not operate anywhere near coffin corner. I think that I read here at a.net that there are very simple rules about that

Now days you don't see it like the old 727 days BUT if you go to a max flt lvl and try to keep an "econ" or higher mach you better be sure it isn't bumpy or you will see the airspeed go red. It isn't like some older jets where you might see 25kts spread but it isn't something you can ignore either.
Of course, the co. teachs that you will burn more to go higher than opt. so you try not to do it if you can.
 
nwafflyer
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RE: High Altitude Cruising

Thu May 19, 2005 9:37 am

OK, so FL41 is a magic number -- never seen by us passengers. I am just so confused about the Pinnacle crash -- the plane was certified to FL41, (now it is not), and although I hate flying on the CRJ 200 (cramped, can't move -- no shoulder/leg/hip room -- even in the exit row seats) they do transport me where I want to go -- my own problem if I need a crane to get off the plane.

OK, so how high do we fly? On an A330 transatlantic, we rarely get higher than 35,000 ft -- why would WN or another domestic carrier go above FL41???????????????????
 
Lemmy
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RE: High Altitude Cruising

Thu May 19, 2005 11:04 am

So Phil, tell us what it's like to descend 31,100ft in 4 minutes in a big ol' 747.

That must be quite a ride!
I am a patient boy ...
 
OPNLguy
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RE: High Altitude Cruising

Thu May 19, 2005 11:07 am

Quoting Nwafflyer (Reply 21):
I am just so confused about the Pinnacle crash -- the plane was certified to FL41, (now it is not),

To the best of my knowledge, it's technically still certified for FL410, but it's just restricted to lower due to the Pinnacle accident. After the investigation is concluded, perhaps the restriction will be lifted, perhaps not...

Quoting Nwafflyer (Reply 21):
why would WN or another domestic carrier go above FL41?

WN wouldn't go above FL410 because FL410 is the limit for the -700s...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
Goldenshield
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RE: High Altitude Cruising

Thu May 19, 2005 11:38 am

OPNL --

We artificially restrict our CRJ's due to that. The stupid thing though, is that we're flying a stretched business jet, which, by all means, should go to 410, but when fully loaded, I'm lucky to get a plan for 350 on some days.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
OPNLguy
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RE: High Altitude Cruising

Thu May 19, 2005 11:48 am

I know what you mean. It'll get better this summer, Oh, wait, no it won't...  Wink

Wondering if we'll hit MOT in PHX or LAS this summer....
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
AR1300
Posts: 1686
Joined: Mon Feb 07, 2005 1:22 pm

RE: High Altitude Cruising

Thu May 19, 2005 12:44 pm

Quoting OPNLguy (Reply 23):
WN wouldn't go above FL410 because FL410 is the limit for the -700s...

But they guy actually said ''ladies and gentlemen this is your Captain from the flight deck .....41,000 feet....''.I heard it.And why would he lie?

Mike
You are now free to move about the cabin
 
OPNLguy
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RE: High Altitude Cruising

Thu May 19, 2005 12:52 pm

Being -at- FL410 (which is OK) and being -above- FL410 (which isn't OK) are two different things...  Wink
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
AJ
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RE: High Altitude Cruising

Thu May 19, 2005 2:00 pm

Ferrying an empty (just two pilots and four cabin crew) 767-300 a few months ago we climbed to the optimum altitude of FL430 (optimum was about 425). The ceiling is 43,100. For practice and to demonstrate to the cabin crew we conducted a rapid descent to 10,000' using the Boeing clean technique (idle thrust, full speed brake). The cabin crew all commented at how gentle it was, they'd been led to believe a rapid descent would have them pinned to the ceiling! Then again there wasn't a hole in the aeroplane.....
 
Key
Posts: 93
Joined: Sat Feb 12, 2005 10:35 am

RE: High Altitude Cruising

Thu May 19, 2005 11:35 pm

Higher cruising levels may save fuel, depending on the temperature and wind at that level. However, true air speed (TAS) will go down as well, costing time. In crowded airspace on the other hand, a high level may get you 'directs' you won't get lower, thus saving you flying time in the end.

ATC can never send any pilot anywhere she/he declines to go for safety or other valid reasons (the reply would have to be 'Unable to comply'). I expect TCAS logic to take into account aircraft performance & limits, but I'm not sure of that.

Erik

P.S. 41000 feet on standard altimeter setting = FL410, not FL41  Wink
 
bhill
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RE: High Altitude Cruising

Fri May 20, 2005 10:25 am

I have been on many NW flights from ORD to SEA in the summer..weather gets kinda nasty...UA also, but those were 757 flights FL410 was quite common over the Rockies..descending into SEA was initially quicker...

Cheers
Carpe Pices
 
greasespot
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RE: High Altitude Cruising

Sat May 21, 2005 10:57 am

The problem with going higher than max cruise it the wing is barely above the stall margin because the air is so thin. You can actually stall the at high altitude and still be going like .83 Mach in a 727....And a stall at that speed and altitude is a very bad thing (so I have been told)

GS
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
 
jfkaua
Posts: 972
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RE: High Altitude Cruising

Sat May 21, 2005 11:52 am

Quoting Greasespot (Reply 31):
The problem with going higher than max cruise it the wing is barely above the stall margin because the air is so thin. You can actually stall the at high altitude and still be going like .83 Mach in a 727....And a stall at that speed and altitude is a very bad thing (so I have been told)

Thats what the "coffin corner" is correct?
 
CosmicCruiser
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RE: High Altitude Cruising

Sun May 22, 2005 12:39 am

Quoting Jfkaua (Reply 32):
Thats what the "coffin corner" is correct?

It's being at an alt. that has you flying at an airspeed that's close to high speed flow separation (stall) and low speed flow separation (stall). You can't go faster and you can't go slower. Not a real problem unless you get into turbulence and the airspeed starts moving around. No reason to ever be there.
 
citationjet
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RE: High Altitude Cruising

Sun May 22, 2005 12:40 pm

The 707 max altitude is 42,000 ft.
The 720 max altitude is 42,000 ft.
The 727 max altitude is 42,000 ft.
The 737-100, -200 max altitude is 35,000 or 37,000 ft.
The 737-300, -400, -500 max altitude is 37,000 ft.
The 737-600, -700, -800, -900 max altitude is 41,000 ft.
The 747 max altitude is 45,100 ft.
The 757 max altitude is 42,000 ft.
The 767 max altitude is 43,100 ft.
The 777 max altitude is 43,100 ft.

The DC-10 max operating altitude is 42,000 ft.
The MD-11 max operating altitude is 43,200 ft.
The L-1011-385-1 max operating altitude is 42,000 ft.
The L-1011-385-3 max operating altitude is 43,000 ft.

Here is a link to the FAA Type Certificate Data Sheet web site that has all the certification information.
http://www.airweb.faa.gov/Regulatory...keModel.nsf/MainFrame?OpenFrameSet

.

[Edited 2005-05-22 05:41:21]
Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
 
gothamspotter
Posts: 311
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RE: High Altitude Cruising

Sun May 22, 2005 2:34 pm

I've experienced FL410 on a jetBlue A320. On JFK-FLL, initial cruise was around FL370, but while off the coast of the Carolinas a line of thunderstorms approached and we climbed to avoid them. The best part is that this (weather radar, flight plan, speed, alt) was all visible on our PTVs.  Smile
 
Tornado82
Posts: 4662
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RE: High Altitude Cruising

Sat May 28, 2005 11:00 am

Quoting Matt72033 (Reply 12):
do engines not suffer a loss of efficiency above 36k feet as they enter the tropopause, where the Temperature remains constant, -57 degrees IIRC, and the static air pressure continues to drop! thus reducing EPR?

Not to be an A-hole, but as a meteorologist I can tell you that you've got some errors here. FL360 is not by any means a magical number for the Tropopause. It varies greatly, and can be well into the 40-50-60k ft range as you get closer to the tropics... and can be even less than FL360. With upper level lows, similar to what socked in the NE US Coast this entire week, the trop can get pretty low. There is also definitely not a "constant" temp across the globe for the troposphere either... it just remains relatively constant (+/- 10C or so) the rest of the way up the flight levels.

Some examples...
Currently (Friday Night) at PIT it is down around 32,900 ft @ -47C
@ EYW (Key West, FL) it is at 52,237 ft @ -75C

Typically, this will be the limiting factor for Cb vertical development. Therefore despite the storms in the PIT area tonight an airliner could, by theory, go right above them no sweat. In EYW, no way, not even a Lear or G-V. If you see Thunderstorm "towers" going up and then levelling off at the top, or "anvilling," that level at which the anvil occurs is a good visual cue to where the trope is that day.

Hope I could be of help, and I certainly didn't mean to offend!

-Todd
 
HaveBlue
Posts: 2104
Joined: Fri Jan 30, 2004 3:01 pm

RE: High Altitude Cruising

Fri Jun 17, 2005 1:19 pm

Interesting stuff there Tornado, thanks!
Here Here for Severe Clear!
 
AirWillie6475
Posts: 2372
Joined: Thu Jan 27, 2005 1:45 pm

RE: High Altitude Cruising

Fri Jun 17, 2005 4:21 pm

I don't think it's a WN thing although I notice that WN usually flys at pretty high altitudes even on short flights. It could however be a 73G winglet thing. I took a flight from LAX to OAK in bad weather and in about 10/15 minutes we were at 40k feet looking at all the could layers, above everything. The 73G climbs fast.
 
PlainSmart
Posts: 99
Joined: Wed May 25, 2005 12:29 am

RE: High Altitude Cruising

Sat Jun 18, 2005 5:33 am

Quoting CosmicCruiser (Reply 14):
"if you can't do 500 fpm in the climb you don't need to go there".

HAH I guess some days we shouldnt even fly in the pattern...
 
anxebla
Posts: 1696
Joined: Tue Dec 23, 2003 8:31 am

RE: High Altitude Cruising

Fri Jun 24, 2005 5:22 am

Quoting PhilSquares (Reply 18):
At max TOW, the 400 will make FL310-320 as the optimum altitude

And what about by the half of the journey, Phil? Is a bit higher, isn't? Last April during an AV flight MAD-BOG (B762) the optimum altitude over the Mid Atlantic was FL370 according to plane computer (we were FL362 on that moment)
AIRBUS 320 The world's most advanced single-aisle aircraft
 
F14D4ever
Posts: 306
Joined: Sat May 07, 2005 3:20 am

RE: High Altitude Cruising

Fri Jun 24, 2005 7:25 am

Quoting Tornado82 (Reply 36):
FL360 is not by any means a magical number for the Tropopause. It varies greatly, and can be well into the 40-50-60k ft range as you get closer to the tropics... and can be even less than FL360. With upper level lows, similar to what socked in the NE US Coast this entire week, the trop can get pretty low. There is also definitely not a "constant" temp across the globe for the troposphere either... it just remains relatively constant (+/- 10C or so) the rest of the way up the flight levels.

Thanks for this very enlightening post. The engineering texts I've seen all list 36089 feet ASL as the 'pause.
"He is risen, as He said."
 
smcmac32msn
Posts: 1661
Joined: Thu May 13, 2004 9:25 am

RE: High Altitude Cruising

Fri Jun 24, 2005 11:03 am

Quoting Prebennorholm (Reply 11):
Fully loaded most planes cannot reach their max certified ceiling. But lightly loaded (most fuel burned and low payload) most planes could climb considerably higher than max certified ceiling. The latter would be done on test flights only, and with test crews wearing oxygen masks.

Also remember the NW CRJ that crashed in Jefferson City, MO was supposedly above its max flight level. R.I.P. the crew of that fateful flight in October.
Hey Obama, keep the change! I want my dollar back.
 
MrChips
Posts: 933
Joined: Wed Mar 30, 2005 2:56 pm

RE: High Altitude Cruising

Wed Jun 29, 2005 10:12 am

Quoting CosmicCruiser (Reply 14):
"if you can't do 500 fpm in the climb you don't need to go there"

Good rule indeed, but its not all that practical here in S. Alberta, where airfields average 2500-3000 feet ASL and higher, and temps routinely exceed ISA+20.

A 172 with 40 gallons of fuel + pilot only on an ISA+20 day will barely be able to maintain 500 fpm right off the runway at most of our airports.
Time...to un-pimp...ze auto!
 
meister808
Posts: 924
Joined: Sat Jan 01, 2000 11:45 am

RE: High Altitude Cruising

Wed Jun 29, 2005 11:05 am

Quoting Smcmac32msn (Reply 42):
Also remember the NW CRJ that crashed in Jefferson City, MO was supposedly above its max flight level.

I have read the CVR transcript, and unless the crew was supposedly intentionally saying false things to make an erroneous CVR transcript, they definitely were at 410, and not higher.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation

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