Max Service ceiling for commercial airplanes

Gig 601XL Builder wrote in
:

Bertie the Bunyip wrote:
Gig 601XL Builder wrote in
news:13q134hrfmbhv24 @news.supernews.com:

Dan wrote:

I've been on commercial flights up to FL410, and (I beleive) FL430.
These were long-haul international flights.

--Dan
I've been on a commercial flight that was at ~FL600.


Not technically commercial since it didn't make money!

You were on a socialist flight!

Bertie


Good point.


Hehe.
Bertie

Bertie the Bunyip wrote:
Gig 601XL Builder wrote in
:

Bertie the Bunyip wrote:
Gig 601XL Builder wrote in
news:13q134hrfmbhv24 @news.supernews.com:

Dan wrote:

I've been on commercial flights up to FL410, and (I beleive) FL430.
These were long-haul international flights.

--Dan
I've been on a commercial flight that was at ~FL600.

Not technically commercial since it didn't make money!

You were on a socialist flight!

Bertie

Good point.


Hehe.
Bertie


But it was the coolest flight I've ever taken commercial. First, I was
only 13 at the time and I got to sit in the jump seat for about 30
minutes including the supersonic transition. And while it was pretty
much a non-event it would have been hard to prove that to a 13 year old
would be pilot.

Gig 601XL Builder wrote in
:

Bertie the Bunyip wrote:
Gig 601XL Builder wrote in
:

Bertie the Bunyip wrote:
Gig 601XL Builder wrote in
news:13q134hrfmbhv24 @news.supernews.com:

Dan wrote:

I've been on commercial flights up to FL410, and (I beleive)
FL430.
These were long-haul international flights.

--Dan
I've been on a commercial flight that was at ~FL600.

Not technically commercial since it didn't make money!

You were on a socialist flight!

Bertie

Good point.


Hehe.
Bertie


But it was the coolest flight I've ever taken commercial. First, I was
only 13 at the time and I got to sit in the jump seat for about 30
minutes including the supersonic transition. And while it was pretty
much a non-event it would have been hard to prove that to a 13 year
old
would be pilot.


Cool. I'd like to have flown it. Who wouldn't?
I have no idea how they got around the various de-pressursation issues.
If there had been a rapid depressurisation at that altitude, well,
oxygen masks wouldn't have saved anyone. I used to know an ex FE on one,
but i never got to ask him much about it.


Bertie

Hi,

In article ,
Bertie the wrote:
Cool. I'd like to have flown it. Who wouldn't?
I have no idea how they got around the various de-pressursation issues.
If there had been a rapid depressurisation at that altitude, well,
oxygen masks wouldn't have saved anyone. I used to know an ex FE on one,
but i never got to ask him much about it.

You could ask Anthony. It was in one of the versions of MSFS but not in the
more recent ones.

Perhaps it was unreliable at that altitude so they removed it?

Andy

Andy Hawkins wrote in
:

Hi,

In article ,
Bertie the wrote:
Cool. I'd like to have flown it. Who wouldn't?
I have no idea how they got around the various de-pressursation
issues. If there had been a rapid depressurisation at that altitude,
well, oxygen masks wouldn't have saved anyone. I used to know an ex
FE on one, but i never got to ask him much about it.

You could ask Anthony. It was in one of the versions of MSFS but not
in the more recent ones.

Perhaps it was unreliable at that altitude so they removed it?


Yes, must strive for ultimate reality!


Bertie

"Dan" wrote

Just guessing, but perhaps the smaller cabin size handles the larger
differential pressure reqiuired better than a big cabin. The extra
expense (and weight) to reinforce a large cabin (ie. heavy jet size)
may not be worth it.

I've been on commercial flights up to FL410, and (I beleive) FL430.
These were long-haul international flights.

I would think it is primarily an economic decision. More fuel to climb
higher, justified only if you can stay that high for a very long time.

Then it also could be the narrowing of the range of speed in "coffin
corner."

Perhaps a real ATP will enlighten us. That isn't me! g
--
Jim in NC

"Bertie the Bunyip" wrote

Another factor is the distance travelled. It makes no sense to go to 410
on
a 200 mile trip. Having said that, the ideal fuel burn profile is close to
straight up and straight down on short trips. No level cruise. IOW, you
keep climbing until you intercept the descent profile and then come down.

Yep, I've been on flights like that. Kinda' strange.

What percentage of power are the engines normally running, on the "coming
down" portion of a flight like that?
--
Jim in NC

"Morgans" wrote in
:


"Bertie the Bunyip" wrote

Another factor is the distance travelled. It makes no sense to go to
410 on
a 200 mile trip. Having said that, the ideal fuel burn profile is
close to straight up and straight down on short trips. No level
cruise. IOW, you keep climbing until you intercept the descent
profile and then come down.

Yep, I've been on flights like that. Kinda' strange.

What percentage of power are the engines normally running, on the
"coming down" portion of a flight like that?

Idle, Right back to the stop is the ideal as far as you can safely do it.
You're supposed ot have the power up to stabilised approach power by about
1,000', bu tit's almost impossible not to touch the taps before then
because of ATC.

Bertie

They're not constrained by revenue considerations and can have fighter jet
type wings and other shapes to allow good buffet margins up there. You
couldn't get a 747 up that high without buffeting it out of the sky unless
it were empty and out of gas!

Is this buffeting related to slow flight? I now remember reading
somewhere, maybe in stick and rudder that large jets do not want to
risk flying very high up at a low airspeed because of the possibility
of an inadvertent stall during turbulence (not sure how much
turbulence exists at FL600 though).

On Jan 30, 11:44*pm, D Ramapriya wrote:
On Jan 30, 2:33 pm, Bertie the Bunyip wrote:



D Ramapriya wrote :

On Jan 30, 2:08 pm, Bertie the Bunyip wrote:
D Ramapriya wrote in
news:2ff47125-cffd-4909-b028-
:

On Jan 30, 8:41 am, WingFlaps wrote:
On Jan 30, 2:03 pm, wrote:

Out of curiosity I was wondering which civilian passenger
airplanes have the highest service ceilings? Wikipedia indicates
that some business jets have ceilings greater than 53000 ft or
so while the 747 has only 43000 ft. Also why do large aircraft
fly much lower than their service ceilings? Usually I never see
a large jet go beyond 37000 or so even on very long haul
flights. I assume they would be even more efficient if they flew
close to service ceilings on long haul flights.

Could be due to weight? When you fly across the Pacific the plane
can only get higher as fuel is burned.

Get higher? I thought that's what the continual small adjustments
effected by the trim wheels do to preclude, especially with the
AutoPilot engaged?

Huh?

Bertie

I meant to say that the AP will ensure that you keep flying at the
programmed altitude (through trim and throttle changes) instead of
letting the plane go higher with diminishing weight. Have I missed
something?

We get cleared to an altitude and have to hold that altitude to avoid
running into other airplanes. The autopilot does not just go where it
pleases.

My point exactly, in response to WingFlaps' "When you fly across the
Pacific the plane can only get higher as fuel is burned".

The AP will anon go where it pleases too on the next-generation
'Buses, albeit in exceptional circumstances.

No, I think you are confused. Altitude is _not_ commanded, Only
thrust and aoa (CL) are commanded flight variables. The plane always
adopts an altitude where lift=weight. The lift is set by the point
where thrust equals drag, the latter set by airspeed, density and CL.
So once you have climbed to maximum altitude (for given fuel burn) you
will gradually drift up as fuel burns. If the max fuel burn is set by
range (e.g. across pacific) or engine performance I think it follows
that max (and/or best cruise) altitude is set by weight OK?

You might command an AP to go to max altitude but if the plane is too
heavy it won't get there and will fly along in a climb attitude (and
maybe even stall at high altitude) until enough fuel has burnt off to
allow it to get there.

Cheers