View Full Version : What's the story with this b-17?

06-14-2007, 11:38 PM

06-14-2007, 11:48 PM
A single experiment with Allison inline engines. Never entered service.

06-15-2007, 12:34 AM
it's pouting??????????????

(good find have never seen that http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif)

06-15-2007, 01:36 AM
Seriously pouting. Had its toy taken away.

06-15-2007, 02:32 AM
The designation XB-40 on the photo is wrong. The XB-40 was an experimental gun ship with more guns that acted as a defence for the other B-17s in formation and carried no bombs.
Later built in a limited number as YB-40 but was no success as they couldn't keep up with the formation after they dropped their bombs on target.

The XB-38 that we see on the picture was an experiment to phase out the R-1820 engines that was near the limits of their development with a new liquid cooled Alison supercharged V-1710-89 engine. Only one built in 42-43 and during test flight it had an uncontrollable engine fire and was abandoned by crew. Co pilot killed when his parachute failed to open.

The project was dropped as little or no performance gains where found with the added weight of the inline liquid cooled engines compared to the radial engines.


06-15-2007, 02:43 AM
XB-38 (http://en.wikipedia.org/wiki/XB-38_Flying_Fortress)
YB-40 (http://en.wikipedia.org/wiki/YB-40_Flying_Fortress)

I believe the Caption has mis-identified this as an XB-40 when in fact it may have been an XB-38

The XB-38 was an experiment to power the Fort with the inline Allison engine. wasn't produced because those engines were needed for P-40's and P-38's

The XB-40 was an attempt to provide better protection for the bomber formations against enemy fighters. It was essentially a B-17 with it's bombload replaced with extra guns and amunition. It was not produced because with the extra weight and drag from all of the guns it was not able to cruise as fast as the normal B-17. By the time they were able to improve the B-40 concept, P-51's were available and they could escort the bombers all the way to Germany, so the project was cancelled.

06-15-2007, 10:07 AM
They also did similiar experiments with the B-29. The XB-39 was a B-29 fitted with 4 Allison V-3420 24 cylinder engines (basically 2 12 cylinder Allison V-1710 engines mated to a common crankcase with a 30? angle between the inner cylinder banks. The crankshafts of the two V-1710 engines were geared together to drive a common propeller shaft).

06-16-2007, 02:40 AM
interested in doing a search? try looking up "5 engine" B-17... and ALSO a SINGLE engine B-17.

one is real , but im not sure about the other one. haven't looked for a while.

06-16-2007, 03:24 AM

Looks odd. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

06-16-2007, 03:33 AM
Converted Lockheed manufactured B-17E.
Re designated the XB-38.
Used P-38 QEC's, was 20mph faster, had a 50 mph higher cruise
speed, could carry a greater payload over a longer distance.
In short, it was a more capable machine than a B-17E.http://www.de220.com/Strange%20Stuff/TEST-80G419784.jpg

Allison had the capability of producing more engines.
If the prototype was not destroyed by an engine fire
things might have been different.

The B-29 conversion to the Allison V-3420 was called
the XB-39. It was far more successful.
Top and cruise speed rose by 60 mph.
Similar gains as the XB-38 in all catagories and in
testing was far more reliable than a standard B-29
powered by R-3350s.

There were a few B-17s converted for engine testing.
One carried a Wright R-3350 in the nose for the B-29 program.
Another tested jet engines.
Yet another tested the Allison T-56 and T-38/T-40 turbo prop
engines. The T-56 went on to power the most successful
cargo plane in history the Lockheed C-130. (in continous production since 1954)

By the was, one of the few "facts" printed in Martin Caidin's books that prove true
is that the B-17 used for T-56 testing could take off and fly on the
turbo prop engine alone.
A T-56-7B was rated for 4,010 hp.
That is nearly as much as all four Wright GR1820-97 s.

Ditto for another B-17 used by Pratt&Whitney
for testing the T-34.
The T-34 was rated in the 7,000 hp class
and saw limited success in several aircraft.

Someone did a nice photoshop job editing out the engines
on N5111N;-)


06-16-2007, 07:13 PM
Good pics of the YB-40 here (http://www.327th.org/327th-org/Greg/yb-40(2).htm).

The YB-40's armament differed from the then-current B-17F as follows:
Chin turret with twin .50s (standardized on the B-17G)
Radio operator's gun replaced with a second Bedix turret like the crew chief's
Single waist guns replaced by dual .50s

There was also additional armor and ammo storage added, while bombs were not carried.

There was also a single XB-41 Liberator that was built to fulfill the same escort duties. Stragely, it had a chin turret instead of the later tail-turret-in-the-nose of later versions of Liberator.

06-16-2007, 08:54 PM
More XB-38 pics here....

06-25-2007, 11:37 PM
Thanks guys for the info. I forgot I made this thread http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif Man it took me 9 days to remember . So it was just a prototype eh? Well I kinda like the look don't you?