D Ramapriya wrote in
:

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. Not yet, anyway.


Bertie