Allison B-17

Saw a photo yesterday of a WWII B-17 test aircraft powered
with four Allison inline engines as opposed to the usual
Wright Cyclones.

Understand the modification added about 800 hp to the
aircraft.

Anyone know why the modification didn't go anywhere?
The usual suspects? Too much disruption to B-17
production? Engines needed by P-38, P-39, P-40?

Sorta "Lanc looking".


SMH

Cant remeber exactly but werent the allison engines unsuitable because they
were no good above a certain altitude!?
"Stephen Harding" wrote in message
...
Saw a photo yesterday of a WWII B-17 test aircraft powered
with four Allison inline engines as opposed to the usual
Wright Cyclones.

Understand the modification added about 800 hp to the
aircraft.

Anyone know why the modification didn't go anywhere?
The usual suspects? Too much disruption to B-17
production? Engines needed by P-38, P-39, P-40?

Sorta "Lanc looking".


SMH

"M. H. Greaves" wrote in message
...
Cant remeber exactly but werent the allison engines unsuitable because
they
were no good above a certain altitude!?

The P-38 had a ceiling of forty thousand feet with Allison inlines.

Brooks

"Stephen Harding" wrote in message
...
Saw a photo yesterday of a WWII B-17 test aircraft powered
with four Allison inline engines as opposed to the usual
Wright Cyclones.

Understand the modification added about 800 hp to the
aircraft.

Anyone know why the modification didn't go anywhere?
The usual suspects? Too much disruption to B-17
production? Engines needed by P-38, P-39, P-40?

Sorta "Lanc looking".


SMH

Stephen Harding wrote:

: Anyone know why the modification didn't go anywhere?

The XB-38 was lost before much testing could be
done. It was slightly faster, but not enough
to make it worth the effort. And the V-1710
was of course much more vulnerable to combat
damage than a radial.

Later Boeing built an XB-39, which was a B-29
with four V-3420 engines, but this too was not
attractive enough to justify production.

Emmanuel Gustin

"M. H. Greaves" wrote in message
...
Cant remeber exactly but werent the allison engines unsuitable because
they
were no good above a certain altitude!?

Depends on which Allison engines

When fitted with a turbo supercharger as in the P-38
they were fine, with a less capable blower setup
as used in the P-40 they were less good but then thats
tue of various marques or Merlin too.

Keith

"Stephen Harding" wrote in message
...
Saw a photo yesterday of a WWII B-17 test aircraft powered
with four Allison inline engines as opposed to the usual
Wright Cyclones.

That would be the XB-38, the ninth production B-17E (41-2401) modified by
Vega with Allison V-1710-89 engines. According to "US Bombers" by Lloyd
Jones, the changes showed an increase in top speed of 10 mph over the B-17E,
with new increased wing fuel tanks giving a range of 3600 miles. The
aircraft was lost on 16 June 1943, 29 days after it's first flight, due to
an in-flight fire.

Anyone know why the modification didn't go anywhere?
The usual suspects? Too much disruption to B-17
production? Engines needed by P-38, P-39, P-40?

The latter reason is the one given in the book.

Jon.

Jonathan Stilwell wrote:

"Stephen Harding" wrote in message
...


Saw a photo yesterday of a WWII B-17 test aircraft powered
with four Allison inline engines as opposed to the usual
Wright Cyclones.



That would be the XB-38, the ninth production B-17E (41-2401) modified by
Vega with Allison V-1710-89 engines. According to "US Bombers" by Lloyd
Jones, the changes showed an increase in top speed of 10 mph over the B-17E,
with new increased wing fuel tanks giving a range of 3600 miles. The
aircraft was lost on 16 June 1943, 29 days after it's first flight, due to
an in-flight fire.



Anyone know why the modification didn't go anywhere?
The usual suspects? Too much disruption to B-17
production? Engines needed by P-38, P-39, P-40?



The latter reason is the one given in the book.

Jon.




Sure is smooth lookin'!!
http://www.wpafb.af.mil/museum/resea...bers/b3-87.htm

Along the same lines I have seen a picture of the XB39, a B29 with the
big 'double Allison' 24 cylinder engine. (2 V12s side by side geared
to a common drive shaft.)
I presume engine bugs forestalled its further development.
Walt BJ

"Stephen Harding" wrote in message
...
Saw a photo yesterday of a WWII B-17 test aircraft powered
with four Allison inline engines as opposed to the usual
Wright Cyclones.

Understand the modification added about 800 hp to the
aircraft.

Anyone know why the modification didn't go anywhere?
The usual suspects? Too much disruption to B-17
production? Engines needed by P-38, P-39, P-40?

Mostly the later, the Vs were going else where.
In the end though, the extra power didn't do much for
the plane's speed: top speed went up 10 mph to 326 mph
but cruise stayed 226 mph. Of course it was carrying a
little extra fuel that stretched max ferry range from
3200 to 3600 miles.
The Air Force Museum will have something up on its
web site. Look under XB-38. The XB-39 would be the
equivalent experiment tried with a B-29

Sorta "Lanc looking".


SMH

WaltBJ wrote:

Along the same lines I have seen a picture of the XB39, a B29 with the
big 'double Allison' 24 cylinder engine. (2 V12s side by side geared
to a common drive shaft.)
I presume engine bugs forestalled its further development.
Walt BJ


From the USAF Museum web site.
"The XB-39 project was basically a proof-of-concept project to
demonstrate performance with liquid cooled 'Vee' engines. It was also
insurance against shortages of the production engine. Only XB-39 was
built; it was delivered the the US Army Air Force in early 1944 for
testing. Most of the problems with the standard B-29 production version
were fixed by mid-1944 and no orders for the XB-39 were placed."
http://www.wpafb.af.mil/museum/resea...bers/b3-88.htm