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High Altitude Cruising  
User currently offlineAr1300 From Argentina, joined Feb 2005, 1740 posts, RR: 3
Posted (8 years 11 months 1 week 6 days 15 hours ago) and read 7458 times:

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


They don't call us Continental for nothing.
44 replies: All unread, showing first 25:
 
User currently offlineTimRees From United Kingdom, joined Aug 2001, 354 posts, RR: 0
Reply 1, posted (8 years 11 months 1 week 6 days 11 hours ago) and read 7356 times:

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'


User currently offlineMIASkies From United States of America, joined Jun 2004, 1340 posts, RR: 1
Reply 2, posted (8 years 11 months 1 week 6 days 11 hours ago) and read 7345 times:

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!
User currently offlinePilotaydin From Turkey, joined Sep 2004, 2537 posts, RR: 51
Reply 3, posted (8 years 11 months 1 week 6 days 11 hours ago) and read 7328 times:

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!
User currently offlineEMBTucano From Brazil, joined Feb 2004, 246 posts, RR: 1
Reply 4, posted (8 years 11 months 1 week 6 days 9 hours ago) and read 7216 times:

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



---- Use GNU/LINUX and be free! ----
User currently offlineSimProgrammer From France, joined Aug 2004, 192 posts, RR: 0
Reply 5, posted (8 years 11 months 1 week 6 days 9 hours ago) and read 7196 times:

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!
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9387 posts, RR: 52
Reply 6, posted (8 years 11 months 1 week 6 days 8 hours ago) and read 7166 times:

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!
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2254 posts, RR: 16
Reply 7, posted (8 years 11 months 1 week 6 days 8 hours ago) and read 7127 times:

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.


User currently offlinePilotaydin From Turkey, joined Sep 2004, 2537 posts, RR: 51
Reply 8, posted (8 years 11 months 1 week 6 days 7 hours ago) and read 7061 times:

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!
User currently offlineGoldenshield From United States of America, joined Jan 2001, 5846 posts, RR: 15
Reply 9, posted (8 years 11 months 1 week 6 days 6 hours ago) and read 7028 times:

In some latitudes, max altitude is also dependant on ozone concentration.


Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlineLemmy From United States of America, joined Dec 2004, 258 posts, RR: 0
Reply 10, posted (8 years 11 months 1 week 6 days 6 hours ago) and read 7013 times:

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 ...
User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6298 posts, RR: 54
Reply 11, posted (8 years 11 months 1 week 6 days 3 hours ago) and read 6943 times:

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, Preben Norholm
User currently offlineMatt72033 From United Kingdom, joined May 2005, 1617 posts, RR: 4
Reply 12, posted (8 years 11 months 1 week 6 days 3 hours ago) and read 6920 times:

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?

User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6298 posts, RR: 54
Reply 13, posted (8 years 11 months 1 week 6 days 2 hours ago) and read 6889 times:

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, Preben Norholm
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2254 posts, RR: 16
Reply 14, posted (8 years 11 months 1 week 6 days 1 hour ago) and read 6866 times:

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.


[


User currently offlineLemmy From United States of America, joined Dec 2004, 258 posts, RR: 0
Reply 15, posted (8 years 11 months 1 week 6 days 1 hour ago) and read 6852 times:

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 ...
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 16, posted (8 years 11 months 1 week 6 days 1 hour ago) and read 6829 times:

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...


User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6298 posts, RR: 54
Reply 17, posted (8 years 11 months 1 week 6 days ago) and read 6804 times:

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, Preben Norholm
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 18, posted (8 years 11 months 1 week 6 days ago) and read 6785 times:

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.


User currently offlineAR1300 From Argentina, joined Feb 2005, 1740 posts, RR: 3
Reply 19, posted (8 years 11 months 1 week 5 days 23 hours ago) and read 6768 times:

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



They don't call us Continental for nothing.
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2254 posts, RR: 16
Reply 20, posted (8 years 11 months 1 week 5 days 23 hours ago) and read 6749 times:

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.


User currently offlineNwafflyer From United States of America, joined Jul 2004, 1050 posts, RR: 2
Reply 21, posted (8 years 11 months 1 week 5 days 23 hours ago) and read 6754 times:

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???????????????????


User currently offlineLemmy From United States of America, joined Dec 2004, 258 posts, RR: 0
Reply 22, posted (8 years 11 months 1 week 5 days 21 hours ago) and read 6715 times:

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 ...
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 23, posted (8 years 11 months 1 week 5 days 21 hours ago) and read 6720 times:

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...


User currently offlineGoldenshield From United States of America, joined Jan 2001, 5846 posts, RR: 15
Reply 24, posted (8 years 11 months 1 week 5 days 21 hours ago) and read 6702 times:

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.
25 Post contains images OPNLguy : I know what you mean. It'll get better this summer, Oh, wait, no it won't... Wondering if we'll hit MOT in PHX or LAS this summer....
26 AR1300 : 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? M
27 Post contains images OPNLguy : Being -at- FL410 (which is OK) and being -above- FL410 (which isn't OK) are two different things...
28 AJ : 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).
29 Post contains images Key : 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
30 Bhill : 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 ov
31 Greasespot : 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 h
32 Jfkaua : Thats what the "coffin corner" is correct?
33 CosmicCruiser : 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). Yo
34 Post contains links CitationJet : 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 3
35 Post contains images GothamSpotter : 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 thunderstorm
36 Tornado82 : 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 Tropo
37 HaveBlue : Interesting stuff there Tornado, thanks!
38 AirWillie6475 : 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
39 PlainSmart : 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
40 Anxebla : 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
41 F14D4ever : Thanks for this very enlightening post. The engineering texts I've seen all list 36089 feet ASL as the 'pause.
42 Smcmac32msn : 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 Octo
43 MrChips : 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 excee
44 Meister808 : I have read the CVR transcript, and unless the crew was supposedly intentionally saying false things to make an erroneous CVR transcript, they defini
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