Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (3 Viewers)

[wuzak]

If the engine bay of the P-39 and P-63 were the same, would I be right in assuming that the auxiliary supercharger in the P-63 was not actually in the engine bay?

 

[fubar57]

Ahhhhh...the Fw 187 Murmeltier

 

[Shortround6]

If the engine bay of the P-39 and P-63 were the same, would I be right in assuming that the auxiliary supercharger in the P-63 was not actually in the engine bay?

Lets not forget the the P-39E/P-76

Granted it was designed to hold the Continental V-1430 (or some version of it) so may have had some extra length to accommodate that engine which came in handy when they wanted to put the two stage Allison in it when Continental couldn't produce an airworthy V-1430 (or tell Bell/USAAC when one would be available).

 

[nuuumannn]

Why are we arguing about putting in a different engine in the P-39 when Bell actually designed a successor aircraft to the P-39 to hold that very engine?
It's like saying the B-17 would have been a super bomber if Boeing had only put R-3350s in it.

I think you've nailed it, Greg. If the P-39 was as good as it is being trumpeted, why did Bell build the P-63?

 

[GregP]

Well, they DID re-engine a B-17. Here's one with four Allisons.

A very pretty bird, indeed! And here's one with four radials and one big turboprop.

and here's one with four turboprops.

and here's one with a Wright turboprop.

Seems like nobody is satisfied with a war-winning bomber, huh? They weren't stisfied with just the B-17. Here's a B-29 with four ALlison V-3420s.

Here's a jet fighter (McDonnell XF-88) with a turboprop in the nose in addition to the turbojets.

They're NEVER satisfied, are they?

If they had a rating scale for fighters in WWII by country, the P-39 and the Buffalo would be fighting a good bout for the bottom of the heap. Maybe we should have sent hordes of P-39s to the Finns. Look what they did with a few Buffalos, and the P-39 could easily beat a Buffalo ... well ... at low altitudes anyway.

 

[nuuumannn]

Well, they DID re-engine a B-17. Here's one with four Allisons.

Yeah, but when Boeing wanted a better bomber they built the B-29, but again, if the P-39 was living up to expectations, why build the P-63? Why not just put the new engine in the P-39, like other Greg hinted at?

 

[Milosh]

Those B-17s with nose engines were test mules for the nose engine.

 

[Shortround6]

Not the point, Greg, when Boeing wanted a better bomber they built the B-29, but again, if the P-39 was living up to expectations, why build the P-63? Why not just put the new engine in the P-39?

Could have been that while with a very large shoehorn, a set of tin snips and a rather cavalier attitude about weights/balance and CG you could get the engine into the engine bay. However some bright young spark figured out that since the P-39 was skating on very thin ice in regards to cooling with the existing radiator and oil coolers fitting and engine that generated several hundred more HP in the cylinders and flew higher (thinner air doesn't cool as well) they were headed for disaster without larger radiator/s and oil cooler/s?

1125hp to prop plus about 100hp for internal friction plus around 250hp to drive the supercharger equals around 1475hp in cylinders for a cooling load at 15,000ft for the single stage engine.

1125hp to the prop plus about 100hp for internal friction plus around 125hp to drive the engine supercharger plus around 300hp to drive the auxiliary supercharger equals around 1650hp in cylinders, now trying to cool that heat load (about 12% greater) at 22,000ft where the air is only 79% as dense (Lbs per cubic ft) is not going to end well.

Figures are a little rough but do point out the problem.

 

[nuuumannn]

Could have been that while with a very large shoehorn, a set of tin snips and a rather cavalier attitude about weights/balance and CG you could get the engine into the engine bay. However some bright young spark figured out that since the P-39 was skating on very thin ice in regards to cooling with the existing radiator and oil coolers fitting and engine that generated several hundred more HP in the cylinders and flew higher (thinner air doesn't cool as well) they were headed for disaster without larger radiator/s and oil cooler/s?

1125hp to prop plus about 100hp for internal friction plus around 250hp to drive the supercharger equals around 1475hp in cylinders for a cooling load at 15,000ft for the single stage engine.

1125hp to the prop plus about 100hp for internal friction plus around 125hp to drive the engine supercharger plus around 300hp to drive the auxiliary supercharger equals around 1650hp in cylinders, now trying to cool that heat load (about 12% greater) at 22,000ft where the air is only 79% as dense (Lbs per cubic ft) is not going to end well.

Figures are a little rough but do point out the problem.

Yup, about sums it up. Wuz gonna say dat too... ;D

The answer is that the P-39 was not living up to expectations. The combat environment had outgrown it.

 

[Shortround6]

BTW the coolant expansion tank in the P-63 held 1 1/2 gallons per the flight manual, which also says that the P-39 tank held 3 gallons.

 

[GrauGeist]

BTW the coolant expansion tank in the P-63 held 1 1/2 gallons per the flight manual, which also says that the P-39 tank held 3 gallons.

Does it say if the tank was brass or aluminum by any chance?

 

[P-39 Expert]

Why are we arguing about putting in a different engine in the P-39 when Bell actually designed a successor aircraft to the P-39 to hold that very engine?
It's like saying the B-17 would have been a super bomber if Boeing had only put R-3350s in it.

Just timing. The new engine was in production from April 1943 but the new P-63 airframe wasn't ready until that October. Seven months wasted in mid 1943 when those engines could have been installed in P-39s.

 

[buffnut453]

Just timing. The new engine was in production from April 1943 but the new P-63 airframe wasn't ready until that October. Seven months wasted in mid 1943 when those engines could have been installed in P-39s.

Have to disagree here. Seven months is barely enough time to install and flight test a new engine, then you have to change the production lines. Seven months won't get a single souped-up P-39 to a squadron.

Given that Bell already had the P-63 in the works, it makes no sense to syphon off scarce design and engineering resources to up-engine the P-39. Bell clearly felt that the P-39 was at the end of it's development potential. No point investing in a dead-end.

 

[Shortround6]

Just timing. The new engine was in production from April 1943 but the new P-63 airframe wasn't ready until that October. Seven months wasted in mid 1943 when those engines could have been installed in P-39s.

Been over this before, the engine was not in full production and did not pass a type test until Nov 1943, didn't pass WEP test until Dec 1943.

So the basic premise seems to be, take low production engine that had not passed a type test and requires more cooling system capacity than the engine in the P-39 and just cram it into the P-39 which already has problems meeting the cooling requirements of the engine they were already using?

As shown above, even if you do not use the WEP capability of the new engine and only try to use the Military power at a higher altitude (pretty much the whole point of the exercise) you need a totally revamped cooling system to make use of the altitude capability.

Seven months is barely enough time to install and flight test a new engine, then you have to change the production lines. Seven months won't get a single souped-up P-39s to squadrons.

Buffnut is pretty much on the money, you not only need a bigger radiator and oil coolers, you need around 25-30% more airflow through the cooling ducts.
Please go back and see the XP-39, One of the reasons the turbo was dropped was that they had to totally redesign the cooling system for the engine even without a turbo.

Now if you have a limited engineering staff do you work on finishing up the P-63 or do you put it on hold and try to sort through this P-39/two stage engine mish mash.

 

[FLYBOYJ]

Just timing. The new engine was in production from April 1943 but the new P-63 airframe wasn't ready until that October. Seven months wasted in mid 1943 when those engines could have been installed in P-39s.

Also keep in mind that during WW2 (and even today), big component items like engines didn't belong to the manufacturer, they were "Government Furnished Equipment" and any reallocation had to be approved by the government.

 

[gordonm1]

This is one of those ones shown flying in the New Zealand air show

This one looked like 6 50's with only two firing on the left side like #3 was jammed.

 

[Peter Gunn]

What I'm getting from all this discussion is that in order for a Bell aircraft (be it P-39 or P-63) to be competitive with contemporary Luftwaffe types is that the stars need to perfectly align.

First Allison has to be producing the 2 stage engine in quantity no later than mid 1940 (approximately 3 years early?).

Then Bell has to make sure the airframe design is able to fit the engine (from 3 years in the future) with the aforementioned 2 stage supercharger (with sufficient cooling, not to mention W&B)

and the government must be on board with channeling the 2 stage engine to the Airacobra program.

Is that about right or am I missing something? While we're at it, maybe that beer truck runs over a certain procurement officer (drgondog's assessment from an earlier thread) and the Mustang gets the 2 speed 2 stage supercharged Merlin a year early and P-51's are available for LR escort in Mid 1943.

 

[P-39 Expert]

What I'm getting from all this discussion is that in order for a Bell aircraft (be it P-39 or P-63) to be competitive with contemporary Luftwaffe types is that the stars need to perfectly align.

First Allison has to be producing the 2 stage engine in quantity no later than mid 1940 (approximately 3 years early?).

Then Bell has to make sure the airframe design is able to fit the engine (from 3 years in the future) with the aforementioned 2 stage supercharger (with sufficient cooling, not to mention W&B)

and the government must be on board with channeling the 2 stage engine to the Airacobra program.

Is that about right or am I missing something? While we're at it, maybe that beer truck runs over a certain procurement officer (drgondog's assessment from an earlier thread) and the Mustang gets the 2 speed 2 stage supercharged Merlin a year early and P-51's are available for LR escort in Mid 1943.

Standard late 1942 P-39N compared with a contemporary FW190A-6. Pretty competitive. Plus P-39 was more maneuverable and had longer endurance.

 

[P-39 Expert]

Have to disagree here. Seven months is barely enough time to install and flight test a new engine, then you have to change the production lines. Seven months won't get a single souped-up P-39 to a squadron.

Given that Bell already had the P-63 in the works, it makes no sense to syphon off scarce design and engineering resources to up-engine the P-39. Bell clearly felt that the P-39 was at the end of it's development potential. No point investing in a dead-end.

Really only three months to get a new engine into a fighter per Vees for Victory. No production stoppage when the P-39 changed from the -35 to the -63 to the -83 and the -85. The -93 was a bit more complicated but doable in my opinion.

 

[buffnut453]

Really only three months to get a new engine into a fighter per Vees for Victory. No production stoppage when the P-39 changed from the -35 to the -63 to the -83 and the -85. The -93 was a bit more complicated but doable in my opinion.

I refer the honorable gentleman to Shortround's post #866.