Q about WWII a/c

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?

Gerald Sylvester

"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

In a non-pressurized aircraft, the breathing of pure oxygen
is not adequate for sustained pilot survival much above
37,000 feet. They can use oxygen delivered under pressure
to the mask, but only about 1/4 psi of "boost" to the pilot
or it will rupture the lungs.
Engines used mechanical air pumps, large turbochargers and
later they had turbo-compound engines.


"Peter Duniho" wrote in
message ...
| "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
|
|

Peter Duniho wrote:
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'.



Some years ago I climbed up on the wing of a P-47 parked outside of Sun Aviation
in Vero Beach, FL and peeked into the cockpit. The manifold pressure gauge was
redlined at 67", IIRC. I was *very* impressed.

Power came from the ubiquitous R-2800 P&W aircooled engine. That was one huge
airplane... must have been about 2/3 the size of a B-17.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com

G. Sylvester wrote:
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?

Like others have mentioned, a large displacement engine with a
multi-stage blower makes it possible. Of course, at 37,000 feet the
prop is not very effective as the air is so thin so its efficiency
stinks. That extreme altitude is not an effective operational altitude,
as the wing's stall margin is tiny and you wouldn't want to get into a
turning fight. IIRC most air-to-air engagements happened below 20,000
feet. A quick Google search shows the B-29's ceiling at 40,000 ft.

On Fri, 17 Nov 2006 08:02:16 -0500, "Mortimer Schnerd, RN"
mschnerdatcarolina.rr.com wrote:

Peter Duniho wrote:
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'.



Some years ago I climbed up on the wing of a P-47 parked outside of Sun Aviation
in Vero Beach, FL and peeked into the cockpit. The manifold pressure gauge was
redlined at 67", IIRC. I was *very* impressed.

Power came from the ubiquitous R-2800 P&W aircooled engine. That was one huge
airplane... must have been about 2/3 the size of a B-17.

Just "thinking out loud", but that sounds a bit high (67"). I'm
thinking perhaps that was the original "war emergency" limit in WW-II,
but may not be achievable with today's 100LL fuel.

Whatever the current "de-rated" maximum manifold pressure limit is
with 100LL, it still must be impressive!

Bela P. Havasreti

Bela P. Havasreti wrote:
Just "thinking out loud", but that sounds a bit high (67"). I'm
thinking perhaps that was the original "war emergency" limit in WW-II,
but may not be achievable with today's 100LL fuel.

Whatever the current "de-rated" maximum manifold pressure limit is
with 100LL, it still must be impressive!


I talked with the owner of a Corsair last year at the "Corsairs over
Connecticut" show at Bridgeport, CT. He said power was limited to 40"
when burning 100LL as a safety margin against detonation. I'm guessing
if 115/130 was still available then 50" would be safe. IIRC WEP (War
Emergency Power) was close to 60"

Kingfish wrote
I'm guessing if 115/130 was still available.....

I suppose that you meant 115/145....it was 110/130.

Bob Moore, a vetern of thousands of gallons of 115/145
through R-1820s and R-3350s.

Bela P. Havasreti wrote:
Just "thinking out loud", but that sounds a bit high (67"). I'm
thinking perhaps that was the original "war emergency" limit in WW-II,
but may not be achievable with today's 100LL fuel.

Whatever the current "de-rated" maximum manifold pressure limit is
with 100LL, it still must be impressive!



Mea culpa. It appears my memory has been clouded by the years. I just got
through watching two Thunderbolt training films on:

http://www.zenoswarbirdvideos.com/P-47.html followed by reading the excellent
account by Corky Meyer, originally published in Flight Journal back in 2003:

http://findarticles.com/p/articles/m..._n9324510/pg_1

It looks like T.O. power was 52 inches and I believe I saw somewhere you could
go to 55 inches in war emergency power with water injection. Sorry if I
misspoke.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com

Bob Moore wrote:
Kingfish wrote
I'm guessing if 115/130 was still available.....

I suppose that you meant 115/145....it was 110/130.

Bob Moore, a vetern of thousands of gallons of 115/145
through R-1820s and R-3350s.

Yep, can't keep the number straight any more. Was the 115/145 the
purple stuff? BTW, what exactly did those numbers represent?