Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (2 Viewers)

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From Joe B

"On April 10, 1941, two P-39Ds were ordered modified and flight tested under contract AC18373 as flying testbeds for the experimental Continental V-1430-1 supercharged inverted-Vee engine that was expected to deliver 2100 hp. These aircraft were assigned the designation XP-39E. The company designation was Model 23. A third machine was later added to the order as a nonflying static test example. Serials were 41-19501, 41-19502, and 41-71464. I am not sure whether these were newly-built aircraft, or modified P-39Ds that were assigned new serials.

However, the Continental engine was not yet ready when the XP-39E airframes were completed, and the 1325 hp Allison V-1710-47 engine was installed in its place. In pursuit of better high-altitude performance, the -47 engine was equipped with a two-stage supercharger and drove an Aeroproducts propeller."
 
Pbehn
Matthews says the -47 engine was not ready for the first flight of the first airframe, so a temporary engine was used until delivery of the -47 which went into the second aircraft 41-19502. The first aircraft, 41-19501, crashed after 15 hours and still had a temporary engine. The static test airframe was not serialled. The replacement,42-71464, number according to Matthews (rather than 41-71464 Baugher) may have had the -47 engine as it was not mentioned in the part I read. I would suggest reading the Matthews book for any interested because it has a lot of data and each can decide why Bell would lengthen the engine compartment unnecessarily. Since I have begun the book again, I find I overlooked many later detailed parts and tables because when I first read it I was interested in the photos and external parts of the plane for model references. I found an appendix in the back I didn't remember, detailing the markings for the P-400 Airacobra Mk.I. As to whether the P-39Es were converted Ds or not, Matthews says a contract was signed for three aircraft, one to be used for structure tests and two flying. Another contract was signed for the replacement for the crashed bird.
 
After reading through this I think there is some confusion. From what I understand the intended engine was the Continental V-1430-1. This was the engine that wasn't ready so the V-1710-47 was installed instead. Correct me if I'm wrong.
 
FLYBOYJ said:
After reading through this I think there is some confusion. From what I understand the intended engine was the Continental V-1430-1. This was the engine that wasn't ready so the V-1710-47 was installed instead. Correct me if I'm wrong.
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You are both correct. The Continental engine was not ready so the Allison-47 was chosen. The -47 wasn't quite ready so a single stage Allison-35 was installed for flight testing.
 
So far this could go either way,
Vees for Victory says that the first -47 engine was in the Allison altitude test chamber in February of 1942 which makes a first flight in the XP-39E in the middle of March suspect but possible.
It also says that Feb 1942 was when Allison started development testing of the hydraulic drive for the aux supercharger and not the single speed friction clutch drive.

The -47 went through quite a number of specification changes so it is possible that the XP-39 flew with some sort of -47 engine but not one in the final configuration?

Only 7 were initially contracted for, one test engine, two for the XP-39s and to for the XP-63s and two spares. Initial contract called for a 9 1/2 impeller in the aux supercharger.

Yes the XP-39 was initially designed around the Continental V-1430-1.
 
You mean XP-39E, right? The -47 evolved into the -93 with the addition of the hydraulic clutch, 8.1 internal SC gear and new intake manifolds without backfire screens .
 
Wright Field wanted a test acft for the Continental V-1430, contacted Bell to redesign the P-39 to test it. Continental then had to redesign the engine to upright configuration to fit the P-39. Matthews points out the V-1430 "was never ready for the Bell airframe or any other." Bell worked with Wright Field to develop model specs for P-39E. As of Feb 18 1941, power plant selection had not been finalized so both engines were candidates.
 
Either way, the XP-39E was not a standard P-39 airframe. It is reported they tried a laminar flow wing on it, but there is no substantiation.

They tried 3 different tail surfaces on it. The fuselage was lengthened 1.75 feet (21 inches) to accommodate the V-1710-47 engine. They would not likely have done that if the Aux-stage engine had fitted without being lengthened, and subsequent P-63s all had longer fuselages, whether on not they had aux-stage engines installed. What I'm saying is there was no "short-fuselage" P-63 with a single-stage engine; it went into a standard P-63 fuselage.
 
I must have missed something. Weren't these supposed to be simple, obvious changes easily implemented?
 
Actually, with the P-39E they were trying to materially improve the P-39. They DID manage to make it perform better at 20,000 feet and above, but still had the basic design flaws.

No range to speak of, narrow CG envelope, no room for development of the platform (little room to add anything and no excess of power if they DID). It wasn't a BAD airplane, but the existing fighters that generally outperformed it were better in almost all respects, perhaps except for climb at low altitudes. It still had the "don't pull hard on the stick quickly or you'll stall" behavior, and it didn't have all that many redeeming characteristics to make anyone who flew it choose it over the more conventional airplanes, which almost universally had better flying characteristics except for having heavier controls. Most pilots LIKED controls heavier than the P-39 controls. The stick-force-per-g was quite low, making it easy to over-pull into a hard turn. At low altitude, that would be fatal.
 
Glider said:
I must have missed something. Weren't these supposed to be simple, obvious changes easily implemented?
Click to expand...
Glider,

I think you might be missing context. There is one poster who keeps repeating incorrectly that a two stage Allison would fit in a standard P-39 airframe. One two stage Allison appears was fitted to a XP-39E (with a 21" fuselage stretch), or not a standard P-39. The P-39E also had several tail configurations fitted, which appear to have resulted in what became the P-63.

There has been some great data presented here, but required several sleuths to keep it in context and or chronology. Be careful sorting through the information lest you be led astray.

Cheers,
Biff

PS: The above assumes you are just landing in or returning to this thread. My apologies if that's incorrect.
 
GrauGeist said:
Hey Geo...is it my imagination, or is that center cricket making amorous advances on the one to the left?

Asking for a friend, of course.
Click to expand...
Center cricket: "Hey baby, I fly F-15's..."

Left cricket: "I don't play for that team..."

Center cricket:

Right cricket: "Dude, you really aren't paying attention..."
 
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With regards to all recent posts about the P-39E. As as I can see the original contract for the Continental engine was a development contract, it was never going to slot straight in. Once that wasnt available then the whole contract changed. The Continental 1430 was supposed to be a better high altitude engine, as was the Aux supercharged Allisson. But so was the _47 variant of the Allison. Obviously how much better they are is a big difference but when reading various histories they can all be called higher performers than the original.
Changes to the wing chord, span and tail didnt result in any substantial difference in performance so the "E" variant wasnt put into production. However, the P-39N was put into production with an even better engine from the same series of the Allisson. The Aux supercharged version was also continued with the P-63. If the P-39E ever flew with an Aux supercharged engine surely it would be much faster than the single stage Allisson engine and this would have been recorded.

As others have shown mathematically, putting the Aux supercharger in a P-39 frame would have it sitting on its tail, extending the tail by 2 ft just makes it sit heavier on its tail. I think the P-39E with the Aux supercharger didnt fly but was part of the development of the P-63. Engineering drawings without modern CGI can tell you if an engine will fit, it doesnt tell you if you can get a wrench onto all the bolt heads or if a mechanic can access all drain bolts and tighten all hoses. The P-39 had already had issues with things like this with gun access. To me the lengthening of the P-39 E airframe was just part of the P-63 story, nothing to do with the P-39.
 
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