A350 & B787 cruising altitude question
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A350 & B787 cruising altitude question
Just watching on FlightRadar24 a Tui 787 just overhead us here in Kent at FL430, Stuttgart to Manchester.
It seems the 787 along with the 350 have somewhat higher cruise altitudes than say 777 or 330 flights.
Don't think I've ever seen a B777 at FL430, or am I wrong?
It seems the 787 along with the 350 have somewhat higher cruise altitudes than say 777 or 330 flights.
Don't think I've ever seen a B777 at FL430, or am I wrong?
Last edited by Ant; 16th Jan 2021 at 18:09. Reason: oops, edit to put a "0" after FL43, but you knew what I meant!!
A brief Google showed me that of the three aircraft you mention, the 777 has the highest max service ceiling.
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Back in the late 1970s I heard a Europe-bound C-141 call London "with ya at 410" - I was quite astonished that the old banger was as high as that and can't recall ever hearing anybody else above 39000 when having an airband radio on as much as possible was my thing (usually 134.9). Subsequently flew over to Miami on an AA 767 which was mostly at 41000 according to the Captain's announcement...
For a 767 to be at FL 410 it must have been pretty light. Max level was 430, but achievable only at low weights. With the 200 series, 410 was achievable on shorthaul sectors with a full load, but with a full 300 series going longhaul the initial cruise level would be around FL330, maybe reaching 370 towards the end of cruise.
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It was a 200 and I don't recall it being particularly crowded - I had a window seat with no neighbours which suited me very well!
787 and 350 in a class of their own regarding high altitude cruising FL’s at standard weighs. Both with latest wing designs. Traditionally A330’s will fly at higher FL’s than 777’s at comparable weights matching the historical mantra of Airbus having more wing than thrust and vise versa for Boeing. A mate on the 777-300ER used to say his machine had thrust to take them up to FL’s the wing just didn’t want to go to.
B747-400 with RR engines could make FL451, although I only did it once, just to see what it was like. Very high, quiet (due to low IAS) and dark blue, as it turned out. Quite regularly achieved FL410 at the end of the flight, but FL390/400 was more normal.
B787-8 and-9 could make FL430 and we achieved that reasonably often. One remarkable memory I have at lower levels is taking off my headset and hearing the whoosh of opposite direction traffic as they passed 1000ft above or below. Even at M0.85, the flight deck was very quiet.
B787-8 and-9 could make FL430 and we achieved that reasonably often. One remarkable memory I have at lower levels is taking off my headset and hearing the whoosh of opposite direction traffic as they passed 1000ft above or below. Even at M0.85, the flight deck was very quiet.
Most modern airliners are not altitude limited by performance. The Max allowed altitudes are based on the time it takes to reach 10,000 feet in a decompression. Many pilots also assume the Max altitude is simply that number. Depending on the aircraft type it may be a pressure altitude so requesting FL 410 might be above the max allowed altitude.
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Most modern airliners are not altitude limited by performance. The Max allowed altitudes are based on the time it takes to reach 10,000 feet in a decompression. Many pilots also assume the Max altitude is simply that number. Depending on the aircraft type it may be a pressure altitude so requesting FL 410 might be above the max allowed altitude.
Paxing All Over The World
Reminds me of a flight deck visit in 2000 of a VS A343 inbound JNB. Capt speaking about descent and approach, "This wing is so good at flying, it takes time to slow it down and you have to allow for that."
As I understand it, almost from the start, Airbus prioritised economy per seat mile as their USP.
As I understand it, almost from the start, Airbus prioritised economy per seat mile as their USP.
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787-8 generally tends to be thrust limited, whereas the 787-9 tends to be buffet (wing) limited until ISA+10 and thrust limited at higher temperatures. It may very depending on engine type and thrust rating.
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350 and 787 definitely fly higher. The 777 had a max altitude of 43100 but at max takeoff weight you are lucky to get to 30000... every couple hours you do a step climb but she was performed well at lower altitudes compared to others
I don't know the details, but there was a change to the regulations regarding depressurization after the 747-400 was certified that basically limits newly certified aircraft to 43k (43,100 ft. if you want to get anal about it).
Regarding the 767, it depends on the engines. I went on a flight test on the 767 AOA ( https://www.globalsecurity.org/space/systems/aoa.htm ) many moons ago where we cruised around for hours at 43k - but it had JT9D-7R4 engines (~50k rating) and to get to those altitudes they had to strip out most of the interior to save weight (what I really remember is that they'd stripped out much of the insulation and it was really, really cold in the cabin).
The later versions of the 767-200 with CF6-80C2 or PW4000 engines could be rated as high as 60k and could easily make it to 43k if they weren't too heavy.
Regarding the 767, it depends on the engines. I went on a flight test on the 767 AOA ( https://www.globalsecurity.org/space/systems/aoa.htm ) many moons ago where we cruised around for hours at 43k - but it had JT9D-7R4 engines (~50k rating) and to get to those altitudes they had to strip out most of the interior to save weight (what I really remember is that they'd stripped out much of the insulation and it was really, really cold in the cabin).
The later versions of the 767-200 with CF6-80C2 or PW4000 engines could be rated as high as 60k and could easily make it to 43k if they weren't too heavy.
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777-200. 43,100ft
777-300 43,100ft
787-8 43,100ft
787-9. 43,100ft
787-10, 41,100ft
Aircraft generally fly higher the lighter they are so, on the same route at any given point, a 777-200 would be higher than a -300 and a 787-8 would be higher than a -9 which would be higher than a -10. Obviously at the moment passenger aircraft aren't carrying huge payloads so they are flying higher than would be normal in better times.
I have..
..(777-200)...
From memory I think the published ceiling for both the -200 and -300 was 431 but I agree with the previous comments about the -300..it wasn't really a "high flyer" in comparison with the original "light twin".
As eckhard says the 744 was FL 451 but I was only ever in the position on that machine once where weight etc made it possible to go up here but because of time remaining to destination it didn't make sense to do so.
..(777-200)...From memory I think the published ceiling for both the -200 and -300 was 431 but I agree with the previous comments about the -300..it wasn't really a "high flyer" in comparison with the original "light twin".
As eckhard says the 744 was FL 451 but I was only ever in the position on that machine once where weight etc made it possible to go up here but because of time remaining to destination it didn't make sense to do so.
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It was a change to 14 CFR 25.841 in 1996, amendment 25-87.
wiggy
Yes, only once for me too. Lagos-LHR with about 80 passengers. We were over northern Algeria at the time (so about 2.30 to TOD) and thought if we don't do it now, we never will.
As eckhard says the 744 was FL 451 but I was only ever in the position on that machine once where weight etc made it possible to go up here but because of time remaining to destination it didn't make sense to do so.
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Many thanks for all replies, really interesting subject.
Just one purely hypothetical question on the subject of cruising altitudes if I may...
Assuming just for a moment that neither engines nor wings are a limiting factor in determining max cruising altitude, does there come a point where the limiting factor is the increasing differential air pressure with increasing altitude between the interior and exterior of the fuselage pressure vessel?
To put it crudely, "don't taker her any higher or she'll burst"!
Just one purely hypothetical question on the subject of cruising altitudes if I may...
Assuming just for a moment that neither engines nor wings are a limiting factor in determining max cruising altitude, does there come a point where the limiting factor is the increasing differential air pressure with increasing altitude between the interior and exterior of the fuselage pressure vessel?
To put it crudely, "don't taker her any higher or she'll burst"!
A good question and it would be a factor if one tried to hold a particular constant cabin altitude as one climbed. In practice, the pressure relief valves would crack open at a pre-determined “delta-P” (differential pressure) and so catastrophe would be avoided. The cabin altitude would then increase as aircraft altitude increased, so oxygen and pressure-breathing would become necessary eventually.