psimpson From United Kingdom, joined May 2006, 250 posts, RR: 0 Posted (4 months 1 week 2 days 4 hours ago) and read 2225 times:
I am just viewing CLX781 B744 LX-UCV on Casper LHR flight tracker at FL450 time 13.28 local.
I have never seen a commercial aircraft cruise at this height? this must be close to the service ceiling for a B747!
seabosdca From United States of America, joined Sep 2007, 3754 posts, RR: 4 Reply 1, posted (4 months 1 week 2 days 4 hours ago) and read 2213 times:
That (well, 45,100) is the ceiling for a 747. You don't see it often because the 747 can only get there when it is extremely light. No other current airliner type is certified to fly that high.
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It is possible as seabosdca posted, 45,100 feet is possible. I haven't been that high with the 744 as we are usually too heavy. And I don't like flying that high. 40,000 feet is enough for me
horstroad From Germany, joined Apr 2010, 117 posts, RR: 0 Reply 3, posted (4 months 1 week 2 days 3 hours ago) and read 2122 times:
Quoting wilco737 (Reply 2): And I don't like flying that high. 40,000 feet is enough for me
why that? scared of hights?
On Sunday evening the sky was so clear we could see FRA from 135nm distance cruising at FL210. imagine the range of sight at FL450... Unfortunately I have not had the pleasure yet
Radiation increases exponentially in the high 30s/low 40s. There was a recent internal study here with regard to atmospheric radiation, with pilots wearing detection devices. It was shown that, by far, the highest radiation was found on the E190s, as they fly the highest.
Also, at some airlines, mine included, when cruising above FL410, one pilot must be wearing an oxygen mask at all times ... not pleasant.
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Any particular reason for this aircraft flying higher than others? Aren't they certified to FL410, as most other airframes? I have certainly been that high on 737NGs several times.
longhauler From Canada, joined Mar 2004, 3305 posts, RR: 25 Reply 6, posted (4 months 1 week 2 days 2 hours ago) and read 2053 times:
Quoting XaraB (Reply 5): Any particular reason for this aircraft flying higher than others? Aren't they certified to FL410, as most other airframes? I have certainly been that high on 737NGs several times.
It is all a matter of economy, and flight plans plan to the best economy. While many aircraft are certified to high altitudes, rarely can they get there. Or if they could, it would not be as efficient as flying lower.
Newer designed wings are more efficient at higher altitudes, as aircraft design evolved, economy was more important that speed. With exceptions, jet aircraft are faster at lower altitudes. For example, M0.80 is slower at FL410 than FL350.... but more efficient at higher altitudes.
If you look at the two examples mentioned, the E190, and the B737NG, it would make sense .... newer designs. Also note, it is also a matter of a varying airframe on a like wing. For example, the E190 is more likely to be higher than the E195 ... and the B737-700 over the -800 or -900.
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RoseFlyer From United States of America, joined Feb 2004, 7619 posts, RR: 51 Reply 7, posted (4 months 1 week 2 days ago) and read 1993 times:
The reason why the 747 is certified up to FL450 is for cargo operators like Cargolux when they ferry an empty freighter or a very light freighter, which is more common than in the passenger business. A 747 carrying passengers will almost never get above 410. By getting above 410, they have the skies clear for them and can take more direct routings, which is very useful over busy airspace such as Europe. Even if it is not the optimal cruise, the airlines will often prefer to get the airplanes up their to save time and fuel via having a more direct routing. The fact that the flight in question immediately climbed to 390 indicates it was probably empty.
Quoting longhauler (Reply 4): Also, at some airlines, mine included, when cruising above FL410, one pilot must be wearing an oxygen mask at all times ... not pleasant.
From what I've been told pilots hate flying at 410 and above because of the oxygen requirements.
Quoting longhauler (Reply 6):
If you look at the two examples mentioned, the E190, and the B737NG, it would make sense .... newer designs. Also note, it is also a matter of a varying airframe on a like wing. For example, the E190 is more likely to be higher than the E195 ... and the B737-700 over the -800 or -900.
Some of the narrowbodies are very capable of climbing high and often are more capable in normal operations than widebodies. The E170 & E190 and the 737NG are great climbers and can often actually climb to 410 unlike the widebodies which can only make it that high at the end of their flights as fuel burns off if at all. Part of the reason why the newest narrowbodies can climb higher is that airlines request it to get more direct routes. It was a marketing decision why the 737NG was designed to fly up to 410 so that it could fly higher than the rest of the narrowbody competition (A320 and MD90 at the time).
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Speedbird741 From Portugal, joined Aug 2008, 622 posts, RR: 0 Reply 8, posted (4 months 1 week 1 day 17 hours ago) and read 1811 times:
Quoting RoseFlyer (Reply 7): A 747 carrying passengers will almost never get above 410
I've had the pleasure of flying onboard a South African Airways 747-400 (Bloemfontein, I believe) at 43,000 feet from Luanda to Johannesburg. And, to my luck, it was a day with exceptionally high visibility
Other than that time, the most I've gone up to on a 747 is 39,000.
Speedbird741
Boa noite Faro, Air Portugal 257 climbing flight level 340
Chimborazo From United Kingdom, joined Sep 2011, 48 posts, RR: 0 Reply 10, posted (4 months 1 week 23 hours ago) and read 1538 times:
Quoting longhauler (Reply 6): Newer designed wings are more efficient at higher altitudes, as aircraft design evolved, economy was more important that speed. With exceptions, jet aircraft are faster at lower altitudes. For example, M0.80 is slower at FL410 than FL350.... but more efficient at higher altitudes.
With regard to the above, is M0.80 "actually" slower at higher altitudes in your example? I appreciate the speed of sound decreases as altitude increases, but so does IAS. Would you be able to explain with numbers why it would actually be slower. Not that I doubt it, just can't get my head around it!
tdscanuck From Canada, joined Jan 2006, 11033 posts, RR: 72 Reply 11, posted (4 months 1 week 21 hours ago) and read 1482 times:
Quoting Chimborazo (Reply 10):
With regard to the above, is M0.80 "actually" slower at higher altitudes in your example?
Yes.
Quoting Chimborazo (Reply 10): I appreciate the speed of sound decreases as altitude increases, but so does IAS.
True, but at high altitude airliners don't fly IAS, they fly Mach.
Quoting Chimborazo (Reply 10): Would you be able to explain with numbers why it would actually be slower. Not that I doubt it, just can't get my head around it!
Speed of sound in standard atmosphere at FL310 is 302 m/s. Mach 0.8 = 242 m/s (470 knots TAS)
Speed of sound in standard atmosphere at FL410 is 295 m/s. Mach 0.8 = 236 m/s (459 knots TAS)
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