QantasHeavy From Australia, joined Jan 2005, 379 posts, RR: 1 Posted (5 years 5 months 6 days 13 hours ago) and read 7390 times:
I have been a frequent flyer for more than 10 years and have never flown above 41,000 feet. Been on over a hundred 747-400s, 777s etc. that are capable of flying higher, but FL410 always seems to be the top. I have had work colleagues say they have been to 43,000 feet in the 777 going to the Middle East and some claim 45,000 in the 747 near the top of descent. They seem to be credible, but I have never done it.
Is this a function of the airways/ATC, the hassle of an SOP stating one pilot must wear an O2 mask above FL410, or the load/performance of the aircraft... or all of the above?
Concorde obviously flew very high and private jets go way up there too. Any reasons why the 787 and A350 generation would not be designed to go higher -- doesn't it save more fuel? Certainly should be a smoother ride.
RSBJ From United States of America, joined Jan 2006, 152 posts, RR: 0 Reply 1, posted (5 years 5 months 6 days 13 hours ago) and read 7395 times:
It doesn't always save fuel climbing higher. At any weight, an aircraft has an optimum altitude and climbing above it usually carries a slightly higher fuel burn penalty than being the same amout below optimum. Our 737-700W's have an optimum altitude of FL400 at 130,000lbs. Cruising at FL390 has a fuel burn penalty of roughly 1%, where FL410 would be 1.3%.
Also, during certification, the plane must be able to descend to 14,000' in four minutes or less from it's maximum certified altitude. I'm told this is why the 737NG was not certified to FL430, it is too slick, and/or it's speed brakes are not effective enough, to make it down in time.
One more item; one pilot must put on his oxygen mask above FL410, so some pilots are discouraged from climbing above FL410.
QantasHeavy From Australia, joined Jan 2005, 379 posts, RR: 1 Reply 2, posted (5 years 5 months 6 days 12 hours ago) and read 7358 times:
Thanks RSBJ.
I wonder how Concorde handled this. Assume one pilot had to be on O2 and if there had been a depressurisation of that cabin at 55,000 feet it could make the descent without overspeeding because it was a high-speed aircraft.
LongHauler From Canada, joined Mar 2004, 4281 posts, RR: 36 Reply 3, posted (5 years 5 months 6 days 11 hours ago) and read 7353 times:
In Canada, when cruising above FL410, one of the pilots must be continuously on oxygen. This adds other considerations, as not only is it cumbersome to wear, but also, Oxygen capacity now becomes an issue.
I am not sure what happens on Concorde, as I am not sure that any mask would work at such a high altitude! One would almost need a pressure suit.
This in mind, I have always found it curious that some (but not all) BAC-111s did NOT have a passenger oxygen system installed at all! I can only assume that they had a very fast descent rate to lower altitudes. I have always found it interesting that any passenger transport aircraft would be licenced in North America without oxygen masks at the passenger seats. (Some versions of the Trident also were not equipped with masks!)
Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
Tb727 From United States of America, joined Jun 2005, 1375 posts, RR: 4 Reply 4, posted (5 years 5 months 6 days 9 hours ago) and read 7306 times:
Quoting RSBJ (Reply 1): It doesn't always save fuel climbing higher. At any weight, an aircraft has an optimum altitude and climbing above it usually carries a slightly higher fuel burn penalty than being the same amout below optimum. Our 737-700W's have an optimum altitude of FL400 at 130,000lbs. Cruising at FL390 has a fuel burn penalty of roughly 1%, where FL410 would be 1.3%.
Plus 99% of the time you get way better winds in the mid-30's, at least over the US. I'd rather be at FL350 and have a ripping tail wind than be up high just to be up high.
CanadianNorth From Canada, joined Aug 2002, 3371 posts, RR: 10 Reply 5, posted (5 years 5 months 6 days 8 hours ago) and read 7262 times:
Quoting LongHauler (Reply 3): have always found it interesting that any passenger transport aircraft would be licenced in North America without oxygen masks at the passenger seats.
Makes perfect sence, as there are a selection of jets (as you stated), and many many turboprops without passenger oxygen masks. Just limit it to altitudes low enough so you don't need them, and your set.
LongHauler From Canada, joined Mar 2004, 4281 posts, RR: 36 Reply 6, posted (5 years 5 months 6 days 6 hours ago) and read 7232 times:
Quoting CanadianNorth (Reply 5): Makes perfect sence, as there are a selection of jets (as you stated), and many many turboprops without passenger oxygen masks. Just limit it to altitudes low enough so you don't need them, and your set.
You are right, as most turboprops are restricted to FL250 as they have either no masks, or only one air cycle machine. But I look at jets like the BAC111 which has no masks, (but two AC packs), and it is not altitude restricted. On the jet transports I have flown, if we had no masks available, (for whatever reason) we would be restricted to FL250 regardless of the number of packs, or ACMs.
I just wonder how the BAC111 got licenced in Canada and the US.
Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
Viscount724 From Switzerland, joined Oct 2006, 21507 posts, RR: 24 Reply 7, posted (5 years 5 months 6 days 6 hours ago) and read 7211 times:
Quoting LongHauler (Reply 3): I have always found it interesting that any passenger transport aircraft would be licenced in North America without oxygen masks at the passenger seats. (Some versions of the Trident also were not equipped with masks!)
If memory correct, many Caravelles also lacked passenger oxygen maks.
Flipdewaf From United Kingdom, joined Jul 2006, 1528 posts, RR: 1 Reply 8, posted (5 years 5 months 6 days 5 hours ago) and read 7203 times:
Quoting LongHauler (Reply 3): This in mind, I have always found it curious that some (but not all) BAC-111s did NOT have a passenger oxygen system installed at all! I can only assume that they had a very fast descent rate to lower altitudes. I have always found it interesting that any passenger transport aircraft would be licenced in North America without oxygen masks at the passenger seats. (Some versions of the Trident also were not equipped with masks!)
The bac1-11s were able to deploy the reversers in flight, much like a C-17can, and achieve desent rates of over 10,000fpm. I would think that this was the reason that it dpesnt have oxygen masks.
Quoting QantasHeavy (Reply 2): I wonder how Concorde handled this. Assume one pilot had to be on O2 and if there had been a depressurisation of that cabin at 55,000 feet it could make the descent without overspeeding because it was a high-speed aircraft.
IIRC Concorde had enough bleed air and was able to remain pressurized at 55,000ft even if one (or maybe two) of the windows blew out. I think this was one of the reasons for the small windows.
CptSpeaking From United States of America, joined Apr 2006, 639 posts, RR: 1 Reply 9, posted (5 years 5 months 6 days 5 hours ago) and read 7175 times:
Quoting LongHauler (Reply 3): This in mind, I have always found it curious that some (but not all) BAC-111s did NOT have a passenger oxygen system installed at all!
Did you know that on the ATR, there may be ~70 seats, but there are only 14 oxygen masks in the back? Better be able to scrap for them!! Interesting little fact to keep in mind next time you're on one listening to the FA briefing on the use of the masks...
Lack of a passenger oxygen system isn't that much of an issue in my opinion, especially if you can get down fast. Worst case, a couple people pass out and wake up again when the fun is over...
Pilotpip From United States of America, joined Sep 2003, 3084 posts, RR: 12 Reply 10, posted (5 years 5 months 6 days ago) and read 7071 times:
Quoting QantasHeavy (Reply 2): I wonder how Concorde handled this. Assume one pilot had to be on O2 and if there had been a depressurisation of that cabin at 55,000 feet it could make the descent without overspeeding because it was a high-speed aircraft.
Concorde had a special exemption. Also at those altitudes I belive that the crew not only had to be on O2, but I believe it had to be pressure breathing.
Bellerophon From United Kingdom, joined May 2002, 574 posts, RR: 60 Reply 11, posted (5 years 5 months 5 days 22 hours ago) and read 7033 times:
RSBJ
...One more item; one pilot must put on his oxygen mask above FL410...
Not always, it depends on the rules of the regulatory authority under which you are operating. I believe you are correct for operations under FAA regulations, but there is no such requirement if operating under UK CAA/JAA regulations.
QantasHeavy
...I wonder how Concorde handled this. Assume one pilot had to be on O2...
You know what they say about assumptions.
No such requirement on Concorde, as it operated under UK CAA regulations and certification.
PilotPip
...Also at those altitudes I belive that the crew not only had to be on O2, but I believe it had to be pressure breathing...
Correct. The flight crew had rapid-donning pressure breathing masks immediately available to them, and were tested and timed once a year by an AvMed doctor, in the correct fitting and use of them.
SuseJ772 From United States of America, joined Aug 2005, 625 posts, RR: 1 Reply 13, posted (5 years 5 months 9 hours ago) and read 6514 times:
Quoting CptSpeaking (Reply 9): Lack of a passenger oxygen system isn't that much of an issue in my opinion, especially if you can get down fast. Worst case, a couple people pass out and wake up again when the fun is over...
I have always thought this as well. As long as the pilot has access to the masks, I feel comfortable that he can get the plane down to an altitude where I'll recover from lack of oxygen before any brain damage.
After all, last I checked with physics, getting planes down was rarely a problem
Max Q From United States of America, joined May 2001, 3293 posts, RR: 19 Reply 14, posted (5 years 4 months 4 weeks 1 day 22 hours ago) and read 6396 times:
Been to 430 in a 767 200, one of the advantages that altitude can give you is to climb above the worst of the headwinds.
The best contribution to safety is a competent Pilot.
Jhooper From United States of America, joined Dec 2001, 6195 posts, RR: 13 Reply 15, posted (5 years 4 months 4 weeks 1 day 14 hours ago) and read 6334 times:
Also, once you start climbing into the stratosphere, the temperature of the air stops decreasing while the air gets thinner, and climbing higher loses it's value. For some reason, they put 36,000 feet on the ATP written test as the "optimum" altitude, but obviously there are variables to consider.
Last year 1,944 New Yorkers saw something and said something.
A342 From Germany, joined Jul 2005, 4655 posts, RR: 4 Reply 17, posted (5 years 4 months 5 days 13 hours ago) and read 5674 times:
Quoting SuseJ772 (Reply 13): I have always thought this as well. As long as the pilot has access to the masks, I feel comfortable that he can get the plane down to an altitude where I'll recover from lack of oxygen before any brain damage.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 18, posted (5 years 4 months 4 days 4 hours ago) and read 5387 times:
Quoting LongHauler (Reply 6): But I look at jets like the BAC111 which has no masks, (but two AC packs), and it is not altitude restricted. On the jet transports I have flown, if we had no masks available, (for whatever reason) we would be restricted to FL250 regardless of the number of packs, or ACMs.
I just wonder how the BAC111 got licenced in Canada and the US.
The BAC 1-11 has is certified to 25,000, 35,000 or 40,000 feet depending on the model and the type of supplemental oxygen system installed.
CaptOveur From , joined Dec 1969, posts, RR: Reply 20, posted (5 years 4 months 4 days 3 hours ago) and read 5353 times:
Quoting CanadianNorth (Reply 5): Makes perfect sence, as there are a selection of jets (as you stated), and many many turboprops without passenger oxygen masks. Just limit it to altitudes low enough so you don't need them, and your set.
I was on a Saab 340 flying for ATA back in 2002 and my best interpretation of the safety card indicated that there was only one mask for 2 passengers on one side. I told the guy next to me he could have the mask, if its bad enough we needed the mask I wanted to be unconscious.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 21, posted (5 years 4 months 4 days 3 hours ago) and read 5353 times:
2H4, the list of serial numbers allowed to operated at 35,000 or 40,000 feet is available in TCDS, A5EU Notes 10. and 11. I assume those seral numbers not listen in the notes are restricted to 25,000 feet.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 23, posted (5 years 4 months 4 days 2 hours ago) and read 5327 times:
Quoting 2H4 (Reply 22): No, I meant range in terms of distance. At 25,000 feet, I can't imagine an already thirsty 1-11 would go very far.
Sometime I don't really understand what I read. As for the range, I have know idea, but agree it would not be far. I read somewhere that the original design was to make an aircraft that was profitable on routes of 100 to 1000 miles. I had a real good friend (a Brit) and he thought the BAC 1-11 was a great aircraft. I would tease him about the "wonder jet".
Thegeek From Australia, joined Nov 2007, 2612 posts, RR: 0 Reply 24, posted (5 years 4 months 3 days 22 hours ago) and read 5287 times:
In answer to the OP, I don't understand why not either. Even with the temperature not dropping off at higher altitudes, the pressure/density will certainly drop, and this is the most important thing. Perhaps it is just too difficult to design engines which are efficient both at sea level and above FL410. And the one pilot wearing an oxygen mask when operating under FAA rules would be highly annoying.
The reduction in winds at high levels would be highly advantageous, as it would allow a given plane to fly longer routes - the direction with the headwinds is the most important one. When in the other direction, you can simply fly lower and probably slower in airspeed terms.
Regarding the descent profile, couldn't you just put on a bigger speed brake, or certify the thrust reversers for in flight use?
Seems a rather obvious method of saving fuel, but it hasn't been done yet.
25 PhilSquares: In response to the original question. On the 744, the max altitude is 45,100 feet. I've been up there several times mainly to avoid weather. In everyd
26 2H4: I believe the original descent question was in reference to emergency descents....not routine ones. I wonder if there are any aircraft types limited
27 PhilSquares: I quickly reviewed the thread and couldn't find it so I just tried to give a general answer. The problem with making speed brakes larger is it requir
28 2H4: Ah, my mistake. I must have just interpreted it that way. Ha, excellent. 2H4
29 Thegeek: Actually, it is there, in Reply 3. Emergency descents are what I was referring to in Reply 24. All design decisions involve trade offs. It could be t
30 PhilSquares: But it's not an engine efficiency issue. The real problem becomes stall protection. Speed brakes the size of barn doors won't alleviate that problem.
31 Thegeek: Umm, if the air temperature and the engine efficiency are constant, the fuel flow will be proportional to the air density assuming the same drag prof
32 PhilSquares: Fuel burn has always been a big issue. Ask anyone who has ever flown LH/ULH. There is a constant battle between payload and fuel. As I said, the issu
33 Astuteman: Echoing a discussion in CivAv - do you recover the bulk of that 500kg back through having a longer descent? Regards
34 PhilSquares: Not really, the descent will begin about 6 miles earlier at 430 v. 410 or about 45 seconds earlier. Fuel on the descent will be about be about 60 kgs
35 Thegeek: I have no doubt that you are correct for the case of the 744. It is not designed to fly at altitudes this high. But take the case of the Concorde. If
36 PhilSquares: Density is affected by temperature and pressure. It's the efficiency of the wing vs. the weight of the aircraft, assuming you're not trying to climb
37 Tdscanuck: Beyond the wing problems, fatigue is a factor. Most of the fuselage on current jetliners is fatigue critical. Increasing altitude increases the diffe
38 BAe146QT: I'm guessing that the problem might be getting the plane down without ripping the control surfaces off. There's a 747SP out there that is a marvellou
39 Tdscanuck: If that were the case, wouldn't you have just demonstrated that your MMo is too low? Tom.
40 PhilSquares: If you follow the FMC or the performance charts, you would be protected since Vs would never be above MMo. However, there have been instances where c
41 Saab2000: This is called Coffin Corner and is not a happy place to visit! The Vs and Mmo meet at that place. Your indicated airspeed is quite low and your Mach
42 BAe146QT: Agreed - either that or you're operating outside the aircraft's published/certified envelope. I should not have used 'MMo' at all, In fact, a simplif
43 BAe146QT: Saab2000 - you posted while I was composing mine and I didn't see yours until now. Many thanks for the answer, especially since the 'horse's mouth' vi
44 Cpd: The main problem is we just don't design planes to fly at those high altitudes. Concorde had no troubles flying at those altitudes (it would go as hi
45 APFPilot1985: Are you talking about the guys in the CRJ? I don't know of anyone doing it in a private jet (and then crashing). I've been up to FL430 a few times in
46 Saab2000: I was once offered a job by a guy who manages airplanes for others. One of their pilots got a shaker/pusher in the low 40s while climbing above the a
47 A342: That was because of pressurization issues, right?
48 Cpd: Something like that. The plane was tested to almost FL690, but FL600 was the selected safe altitude. The higher you go, the more risky it becomes if
49 BWilliams: I think that's the one he's talking about... the ferry flight where the guys went up to 410 just for S&Gs and lost both engines.
50 David L: But wasn't that due to the fact that the cruise climb is very efficient and that Concorde was allowed to do it because of the lack of conflicting tra
52 FlyMatt2Bermud: http://www.airliners.net/uf/view.fil...9016&filename=1149048261vkB3Ff.jpg This is the view from FL510 looking North from over Lakeland, Florida. Our G
53 Thegeek: OK, that explains why you shouldn't avoid the stall speed by flying faster at higher altitudes even with constant engine efficiency. Interesting pict
54 David L: Or a reflection of the winglet? I do know that Concorde was able to fly a bit higher in the equatorial regions due to the tropopause being higher the
55 FlyMatt2Bermud: Heaps of ice? Yikes. I'm sure it is only an illusion, the only ice I've ever seen on that wing would be a trace on the winglet.
56 BAe146QT: Gents - yes, that is the case I was referring to. Agreed. Though the reflection does look sort of rippled which might lead someone to think that ther
57 Thegeek: You're quite correct. I didn't think that much ice would be normal.
58 Cpd: Yes, that's quite correct I think. But one of the respondents above is much better qualified to confirm it.
60 Grunf: Speaking about Concorde, I would like to know what would Concorde's theoretical absolute ceiling be, right below coffin corner? Something like flying
61 Cpd: The highest they've done (that we know about) was 68,700ft. It wasn't an airline production model. It may have been F-WTSB or -F-WTSA. Concorde 208 di
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Interesting little fact to keep in mind next time you're on one listening to the FA briefing on the use of the masks...
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