"G. Sylvester" wrote in message
. com...
I was just at the Museum of Flight which is an *amazing* museum. Many of
the WWII a/c have ceilings of upwards FL370. How do piston and prop a/c
have ceilings that high? Even supercharged engines I presume lose most of
their performance that high. Even more so I'd expect the prop which can't
be 'supercharged,' also must lose most of their performance. Any background
on how they operate so high?

Lots of power, big constant speed props (it's been explained to me that you
don't need to "supercharge" a prop...as long as the blade angle can be
adjusted for the conditions, the prop can deliver whatever power the engine
is generating, just as the wing can generate the same lift equal to airplane
weight regardless of altitude).

It's true that supercharging eventually drops off, but since it makes "sea
level" for the engine start much higher, you can still get pretty high
before you don't have enough power to fly. Keep in mind that while your
true airspeed does need to be higher to keep from stalling the wing, drag is
reduced so the power requirement is lower.

Frankly, I don't find it all that surprising. I own a turbocharged
airplane, essentially turbonormalized (the turbo version is only 20hp more
than the normally aspirated version). Critical altitude for the
turbocharger is about 16000', the airplane is certified for 20000', and I've
spoken with one of the manufacturer's test pilots who says they took the
airplane over 25000' during certification tests.

This is an airplane that's only 270hp, has a boost of only about 4". The
WWII piston airplanes had what, an order of magnitude (at least) greater
power, with boosts of anywhere from 15" to 30"? I'm no expert and I might
have some of those numbers a bit off, but still...if my little recreational
4-seater can get up to 25000', I don't have a hard time at all believing
that one could get a powerhouse piston fighter or bomber up to 37000'.

And yes...the engines do "lost most of their performance that high". That's
why 37000' is the *ceiling*.

Pete