Super P-39?

[R Pope]

Was the P-39 ever proposed as a possible recipient of a Merlin engine? Or even a Griffon! Would that have made it a competitive alternative to, say, a P-40/Merlin, which, judging by the resulting performance gains, was a waste of a Merlin. (!!)
I realize the Griffon was not built in the USA, and so was not a real choice, but the Packard Merlin could have been swapped in. It is physically smaller than the Allison so it would have fit in the fuselage without any humps or bumps.
Even if it was never seriously touted, what are your thoughts on the imaginary results?

 

[R Pope]

OK, I reread some info on the P63 and found reference to a prototype that was to have a Merlin. It was completed with an Allison, though, because the P51 was using up all the Packards. Oh, well, another opportunity lost. You'd think they could have spared one for tests, though.

 

[Shortround6]

Which Merlin?

Everybody wants the performance of the two stage Merlin without paying more than the cost (weight and drag) of the single stage Merlin.

Lumps and bumps will come not from the engine itself but from the intercooler. See the difference in the under wing radiator housings between a MK V Spit and a MK IX.

 

[tomo pauk]

The two stage Merlins were vastly a better engine than the single stage ones, even if the intercooler installation is less-than-ideal, as it was in Spitfire. The Spit IX was both faster and better climber than the Spit V, if we compare the same altitude oriented versions.

1st question about Merlin: can the engine be mated with extension shaft? The V-1710 was a rather modular engine, with reduction gearbox fully detachable, so the extension shaft was rotating at camshaft speed. What was case for Merlin?
2nd question: what would offer the (presumed) Packard Merlin, vs. the historical V-1710? The best performing types, like the -Q subtypes, were making some 385 mph @ ~16500 ft, military power (1125 HP), with external guns. Without external guns, the speed was up some 10 mph, and at WER (1420 HP), no. ext guns, the charts show more than 400 mph at ~10500 ft. No wonder Soviets loved them.
At 23-24000 ft, such planes were still able to do 380 mph. Mind you, those were almost as fast as the P-51A, and somewhere between Spit V and early Spit IX. It was also faster than P-40F (Packard Merlin, 1 stage).
The V-1650-1 makes the rated power (1120 HP) some 3000 ft higher altitude than the V-1710-85 from the P-39Q (18500 ft vs. 15500), the P-39Q engines having the 3500 ft advantage on their on vs. 'plain' P-39D. So the high altitude performance would've received another boost, while the low alt performance would not suffer, due to two-speed supercharger.

In order for the 2 stage Merlin to be installed, the intercooler also needs to be installed, the best spot being maybe under the belly, the drop tanks going under wings. Wings needing some reinforcements.
The engine air intake needs to be at another spot (side of the airplane?), not being shadowed by canopy might allow for better harvesting of ram effect, esp. if the intake is elongated?

The main shortcoming: would the problematic stall behavior get even worse, with heavier engines installed behind CoG?

 

[Shortround6]

Thank you Tomo.

The Idea looks good at first glance and putting in a Merlin 45 or XX (Packard V-1650-1) might only call for a modified block casting without reduction gear and some minor re-piping ( and fiddling with the radiator oil coolers).

Sticking in the Merlin 61 ( V-1650-3) is a whole new can of worms. It is about 200lbs heaver than the single stage engine with the weight and bulk at the back of the engine. Tomo has listed a number of the other modifications needed.

Please remember that the XP-39E was ordered in prototype form April 10, 1941 with Continental V-1430 engines, they were not ready and first flight was made March of 1942 using a two stage Allison engine. The XP-39 used a bigger wing and a fuselage 1.75 feet longer than a normal P-39. Basically, aside from general shape, it was a new airplane and the predecessor to the P-63.

There was a planned V-1650-5 for the P-63 King Cobra but the P-63 had about 2 feet more fuselage than the P-39 in addition to a number of other modifications. You are now pitting the V-1650 two stage engine against the two stage Allisons in the P-63. Power levels are a lot closer at some altitudes.

One reason the P-39 was as fast as it was is because it was a small airplane. Which means there is not a lot of room to stick in bigger superchargers and bigger radiators/intercoolers. At least it seems that is what the Bell engineers thought or they wouldn't have bothered doing so much work on the XP-39E and P-63.

 

[GregP]

The P-39 is a smaller aircraft than the P-63, and I believe the P-63 airframe could take the two-stage Merlin. The Allison with the aux stage was about the same as a two stage Merlin and the difference would have been small. The P-63's with the single-stage ALlisons would have benefited from the two-stage Merlin and it might well have been an excellent idea.

I agree there would be issues with the P-39 though ...

 

[wuzak]

I believe that the 2 stage Merlin was only slightly longer than the V-1710. Weight was about 300lbs heavier.

Not only would you have to have an intercooler radiator for the 60 series Merlin, but also an increase in radiator size to compensate for the extra power.

On the size of the intercooler radiator, note that the small chin on the front of the nacelles of the Mosquito 2 stage variants was for the intercooler. The increase in radiator size for the IX was only partly from intercooling - but mostly from engine cooling.

 

[tomo pauk]

Hi, Greg,
The 2 stage V-1710 was a longer engine than 2 stage Merlin, the installation in the XP-51J was involving relocation of firewall closer to the pilot so the engine can be installed without harming the plane's CoG. The P-63 was equipped with 2 stage V-1710.
What could this refer to:

The P-63's with the single-stage ALlisons would have benefited from the two-stage Merlin

Be it as it was, my super P-39: as good V-1710 as it gets, 3 x .50 cals synchronised, 1 x 20mm, no wing guns, maybe some fuel instead.

 

[Aozora]

The question is what could a Two-Stage Merlin equipped P-63 do that a P-51D or H couldn't do better?

 

[GregP]

Hi Tomo,

That would refer to the 32 RP-63G models without the Aux stage engines.

Today, as far as I know, none of the flying P-63's are running the aux stage even though we have a couple available for overhaul. Of course, none of the P-38's are running the turbos, either, today. I DO know of one P-47 still running the turbocharger. That would be Paul ALlen's in Seattle at the Flying Heritage Collection.

 

[tomo pauk]

Ahh, thanks for explanation re. single stage (Pinballs) P-63.

Hi, Aozora,
Don't think that anybody is convinced that Merlinized P-39 would offer anything more than such a P-51.

 

[GregP]

I'd really like to see a twp-stage Merlin in an XP-40Q, the plane that North American looked at before producing the P-51.

There might be some potential tehre .... maybe not. I was a good airplane, but not better than the P-51, so was not proceeded with. With a two-stage merlin, the tables may well have changed. Perhaps not.

 

[wuzak]

I'd really like to se a twp-stage Merlin in an XP-40Q, the plane taht North American looked at before producing the P-51.

There might be some potential tehre .... maybe not. I was a good airplane, but not better than the P-51, so was not proceeded with. With a two-stage merlin, the tables may well have changed. Perhaps not.

Greg, North American were asked to build the P-40 for Britain, but said they could do better - the result was the P-51.

The XP-40Q was contemporary to the P-51B or D - around that period anyway.

When the British visited NAA the P-40 version under discussion would have been the P-40B/C.

 

[CobberKane]

The question is what could a Two-Stage Merlin equipped P-63 do that a P-51D or H couldn't do better?

I wonder if the Soviets would have taken the P 51 over the P 63, given the choice. I suspect not. The P 51's performance advantage at altitude would have been of little use on the Eastern Front. The P 63 should have been a bit less vulnerable to ground fire – important at low and medium altitudes – and the tricycle undercarriage would have been a big plus on front line runways

 

[GregP]

Wuzak, you need to check your facts. They were shown the entire blueprint set for the XP-40Q and started from there after considering the possibilities. We had many members at the museum who worked for North American and some of them knew it. Do you really think they started from scratch and made a thoroughbred in 120 days with no "assistance?"

If so, how come nobody else in the entire war could do that? Did the Mustang designer ever do it again?

You decide for yourself. I already have an opinion.

 

[wuzak]

Wuzak, you need to check your facts. They were shown the entire blueprint set for the XP-40Q and started from there after considering the possibilities. We had many members at the museum who worked for North American and some of them knew it. Do you really think they started from scratch and made a thoroughbred in 120 days with no "assistance?"

If so, how come nobody else in the entire war could do that? Did the Mustang designer ever do it again?

You decide for yourself. I already have an opinion.

Greg, Curtiss were ordered to hand over data for a laminar flow winged aircraft - this was not a P-40. I don't think it was the XP-46 either, but maybe the XP-53?

Regardless, when NAA designed the P-51 the latest P-40 was the P-40B or P-40C. The P-40D was ordered by the Ministry for Aircraft Production (MAP) in May 1940, 2 months after the P-51 (Mustang I) was ordered by the MAP.

The XP-40Q used a 2 stage Allison (well, at least one, maybe two, of them did) - an engine which didn't exist in 1940.

 

[wuzak]

Not the XP-53, but the P-40 and XP-46's data was purchased from Curtiss:

NAA had purchased the complete set of P-40 and XP-46 wind tunnel data and flight test reports for US$56,000

North American P-51 Mustang - Wikipedia, the free encyclopedia

But it still wasn't the XP-40Q.

 

[GregP]

OK, your take on it. I have other information. Go look at a P-51and an XP-40Q side by side.

I don't believe in that much coincidence.

But I also will not argue too long about it. Let's just say the XP-40Q would have been a very worthy contender had it made production in a very political world.

 

[Shortround6]

If Curtiss had the plans for the P-40-Q in 1940 Curtiss management should have tried for treason.

The First P-40-Q was being flown for handling evaluation in October of 1943.

http://www.wwiiaircraftperformance.org/P-40/P-40Q_42-9987_Eng-47-1660-A.pdf

Even if it took them a full year to build it that means start of construction in Oct of 1942?

Curtiss management would have had to be sitting on the plans for the P-40-Q for 2 1/2 years before starting construction?

And they trotted out such wonders as the XP-55 and the whole sorry P-60 menagerie while they had the P-40-Q plans sitting in drawers?

They may look a lot alike but given the timing if anybody copied anything it was Curtiss.

 

[wuzak]

The XP-46 was originally preferred to take over from the P-40B/C, but it wasn't going to have any better performance than the new P-40D, and would have slowed production, so it was canned.

The XP-46 had a ventral radiator intake, like the P-51, except that it didn't have a boundary layer splitter.

http://1.bp.blogspot.com/-1j45ZiMzm...FbYTQJJ3-I/s1600/XP-46A+Warhawk+40-3054+1.jpg