A342 From Germany, joined Jul 2005, 4655 posts, RR: 4 Posted (4 years 1 month 1 week 1 day 16 hours ago) and read 6959 times:
This question has been on my mind for quite some time, so I'll finally ask.
The A320 family has a certified service ceiling of 39,800 feet (39,100ft for aircraft not equipped with modification 30748, which seems to apply mostly to early aircraft). As aircraft use flight levels which are spaced 1,000ft apart (in RVSM airspace), this seems odd. Wouldn't it be useful to at least gain permission for FL400? Two hundred feet can't be an issue, especially when we consider that the ACJ and A318 Elite (maybe also the A320 Prestige) are in fact certified for 41,000ft.
Same with the A380, B777 etc.: Why are they certified for 43,100ft and not simply 43,000ft?
I'm really wondering, but I'm sure you can help me.
Thanks in advance,
Mandala499 From Indonesia, joined Aug 2001, 6178 posts, RR: 74 Reply 1, posted (4 years 1 month 1 week 1 day 14 hours ago) and read 6906 times:
Quoting A342 (Thread starter): The A320 family has a certified service ceiling of 39,800 feet (39,100ft for aircraft not equipped with modification 30748, which seems to apply mostly to early aircraft).
In Russian airspace, your flight levels near the ceiling are:
11600m (FL381) for westbound and 12100m (FL397) eastbound... so 39800 gives U a 100ft cushion for that...
If the aircraft is restricted to 39100... in Russian airspace U'd be limited to 11100m (FL364) eastbound.
And if you're restricted to FL431... well, doesn't matter much coz westbound FL430 is available (13100m) and eastbound U're going to be at FL397 anyways, unless you want 14100m (FL463)...
Quoting A342 (Thread starter): Same with the A380, B777 etc.: Why are they certified for 43,100ft and not simply 43,000ft?
If you're certified for 43,100, you have that 100ft cushion... if you're restricted to FL430 as your ceiling, you'd be busting your certification of you find your plane at 43,001ft...
Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
A342 From Germany, joined Jul 2005, 4655 posts, RR: 4 Reply 2, posted (4 years 1 month 1 week 1 day 12 hours ago) and read 6853 times:
Quoting Mandala499 (Reply 1): If you're certified for 43,100, you have that 100ft cushion... if you're restricted to FL430 as your ceiling, you'd be busting your certification of you find your plane at 43,001ft...
Thanks, that makes sense.
But regarding the A320, I rather doubt that it was designed primarily for the Russian market. Does China use the same altitudes (metric with 500m separation)?
PhilSquares From , joined Dec 1969, posts, RR: Reply 3, posted (4 years 1 month 1 week 1 day 7 hours ago) and read 6788 times:
Quoting A342 (Thread starter): Same with the A380, B777 etc.: Why are they certified for 43,100ft and not simply 43,000ft?
In the VNAV function, the altitude hold function is soft. The aircraft will accept slight deviations in altitude to maintain a smoother ride for passengers. In the ALT mode, it is a "hard" level hold. If you select FLXXX it will hold that, where as in VNAV you will see slight deviations to allow a smoother ride with fewer throttle inputs and smaller airspeed changes.
Rwessel From United States of America, joined Jan 2007, 1989 posts, RR: 2 Reply 4, posted (4 years 1 month 1 week 1 day 1 hour ago) and read 6735 times:
Quoting A342 (Reply 2): But regarding the A320, I rather doubt that it was designed primarily for the Russian market. Does China use the same altitudes (metric with 500m separation)?
But as you pointed out in your original post, 700ft of ceiling was added to the later models. Presumably there were customers (or potential customers), who were running into the Russian flight levels, and a modest altitude increase could be accommodated with minor modifications (perhaps little more than paperwork, given that the ACJs are certified to more than that).
And yes, China, Mongolia, and many of the countries that were formerly part of the Soviet Union use the metric flight levels.
A342 From Germany, joined Jul 2005, 4655 posts, RR: 4 Reply 5, posted (4 years 1 month 1 week 1 day 1 hour ago) and read 6723 times:
Quoting PhilSquares (Reply 3): Quoting A342 (Thread starter):
Same with the A380, B777 etc.: Why are they certified for 43,100ft and not simply 43,000ft?
In the VNAV function, the altitude hold function is soft. The aircraft will accept slight deviations in altitude to maintain a smoother ride for passengers. In the ALT mode, it is a "hard" level hold. If you select FLXXX it will hold that, where as in VNAV you will see slight deviations to allow a smoother ride with fewer throttle inputs and smaller airspeed changes.
So what about an aircraft that is certified for exactly 41,000ft and cruises at FL410, for example a 737NG? Don't they have VNAV?
Quoting Rwessel (Reply 4): But as you pointed out in your original post, 700ft of ceiling was added to the later models. Presumably there were customers (or potential customers), who were running into the Russian flight levels, and a modest altitude increase could be accommodated with minor modifications (perhaps little more than paperwork, given that the ACJs are certified to more than that).
Well, now the question is why they don't add another 200 or 300ft for customers operating primarily in western airspace? I believe it is relatively common (at least for the A318 and A319) to cruise at FL390. While I don't have any data to back this up, I feel that another 1000ft would make sense for quite a few flights.
PhilSquares From , joined Dec 1969, posts, RR: Reply 6, posted (4 years 1 month 1 week 21 hours ago) and read 6661 times:
Quoting A342 (Reply 5): So what about an aircraft that is certified for exactly 41,000ft and cruises at FL410, for example a 737NG? Don't they have VNAV?
I have never flown the 73 series, however on the 747-400, it's certified for 45100. It has VNAV and at FL 450 it will be a soft cruise in VNAV. I suspect the 73NG is the same in that it's certified for FLXX100.
Mandala499 From Indonesia, joined Aug 2001, 6178 posts, RR: 74 Reply 7, posted (4 years 1 month 1 week 18 hours ago) and read 6619 times:
Quoting A342 (Reply 2): Does China use the same altitudes (metric with 500m separation)?
In China the flight level allocation is different than in Russia... now they use metric RVSM aswell... 300m separation.
Interestingly, if the A320 is restricted to 39,000 max cert alt, then they loose out of 11,900m (FL391)...
Quoting A342 (Reply 5): Well, now the question is why they don't add another 200 or 300ft for customers operating primarily in western airspace? I believe it is relatively common (at least for the A318 and A319) to cruise at FL390. While I don't have any data to back this up, I feel that another 1000ft would make sense for quite a few flights.
Well, I'm told that Air Asia's new A320s are certified to FL400/410 in line with the ACJs...
I'm guessing that the FL397 ceiling was a progressive improvement introduced and later increased again...
Quoting PhilSquares (Reply 6): I have never flown the 73 series, however on the 747-400, it's certified for 45100. It has VNAV and at FL 450 it will be a soft cruise in VNAV. I suspect the 73NG is the same in that it's certified for FLXX100.
I just checked the manuals, it says 41,000ft as the NG's max operating altitude, the 744 does have 45,100. Odd... perhaps it has got to do with the wording and certification????
Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
RoseFlyer From United States of America, joined Feb 2004, 8739 posts, RR: 52 Reply 8, posted (4 years 1 month 1 week 18 hours ago) and read 6619 times:
Quoting A342 (Reply 5): Well, now the question is why they don't add another 200 or 300ft for customers operating primarily in western airspace? I believe it is relatively common (at least for the A318 and A319) to cruise at FL390. While I don't have any data to back this up, I feel that another 1000ft would make sense for quite a few flights.
It might be very expensive to do that. Can the packs take the additional load and still meet the safety requirements? Does the plane have the capability to descend fast enough in an emergency in all configurations in the event of a decompression? Is the skin thickness and structural strength capable of repeatedly taking the higher load within required safety factors? Will increased fatigue occur? Are the seals capable of that pressure differential? Do the engines have enough capability to economically cruise at that altitude with realistic payload?
All of those can be factors. I don't know A320 design, but there is probably something that would be very costly to change that would be required to certify it for a higher altitude. Obviously they can get around it on an ACJ, but that plane does have structural and capacity modifications and is a lower cycle airplane.
200 ft might not seem like much, but it can push some components beyond their required safety factors. It was a massive amount of work to get the 737NG capable of 41,000ft. Boeing went through the cost though so that they could make their plane fly higher than Airbus.
If you have never designed an airplane part before, let the real designers do the work!
Mandala499 From Indonesia, joined Aug 2001, 6178 posts, RR: 74 Reply 10, posted (4 years 1 month 1 week 14 hours ago) and read 6556 times:
Quoting A342 (Reply 9): That's odd. Can't find any reference...
Hence the "I'm told..." as I haven't seen reference to it before apart from claims by crew to be at FL400 (on one occassion they were about to be bumped to 340 by 2 NGs at 360 and 380... how and why that's another story)... if I see reference to it... I'll let you know (if I remember)...
When losing situational awareness, pray Cumulus Granitus isn't nearby !
PGNCS From United States of America, joined Apr 2007, 2511 posts, RR: 45 Reply 11, posted (4 years 1 month 1 day 13 hours ago) and read 6215 times:
Here is a very interesting (although old) discussion of this subject that may be enlightening. Please note the discussion of the 737NG in the future tense!
My understanding of the 757 limitation of 42,000' (versus the 43,000' on the 767) was due to the extra time to descend in the 757 in a decompression incident. Perhaps somebody with applicable knowledge can comment.
Here is yet another discussion of related topics that are germane to this thread:
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Does China use the same altitudes (metric with 500m separation)?
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