Max Service ceiling for commercial airplanes

wrote in
:


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).


Well, actually it;s low and high. When the air going over a wing that's
traveling close to supersonic is accelerated futher by the action of the
wing, it goes supersonic over the wing. When you go too fast, max mach, you
get a loss of lift. When you go too slow, you accelerate the air over the
top of wing as well due to increased angle of attack. If you load the wing
up with weight or G (same thing as far as the wing is concerned) same thing
happens. The air buffeting from the shock wave is similar to a stall ( some
sources call it a stall) and loss of control and altitude results. Recovery
can be difficult, though not impossible. There are a number of other facors
at play here, but that's the meat of it.

Bertie