The P-39 a Zero Killer???

Totalize · Apr 14, 2014

I read that it was the U.S. Army that requested Bell remove the supercharger from the original P39 thereby forever limiting its high altitude performance. The U.S. army also had Bell reduce the fuel capacity of the Aircraft as well to make it lighter. The Air battles in the Pacific were often higher altitude fights which was put the P-39 at a distinct disadvantage. However, on the Eastern front the air battles often took place at low altitude. On this front the P-39 was a credible opponent and achieved I think better success there especially as a ground attack fighter. A number of Guards units only had P39's they liked it so much. I also read the Soviets requested the U.S. stop sending them P-40's and replace them with P39's.

FLYBOYJ · Apr 14, 2014

GregP said:
Good one FlyboyJ!

Seeing a talk by Saburo Sakai was dumb luck on my part.

I went to an art show at Champlin Fighter Museum almost by accident when a friend of mine couldn't go and gave me his tickets. I had no idea who would be there. I wasn't invited ... he was. It was a magic evening by chance because he had another pressing engagement.

I met him at Chino - 1978?

Juha · Apr 14, 2014

GregP said:
...In the reference that quotes the 1 : 3, I wonder where the author got his numbers. I have been searching for Japanese records for many years and have yet to find one, much less one that specifies confirmed victories instead of claims. In fact, I never even HEARD of a Japanese unit that ever mentioned claims versus confirmed victories. I haven't even seen anything in print anywhere that mentions Japanese claims versus confirmed victories unless it was written by western authors who rarely give sources for numbers. The Japanese themselves didn;t keep public records of combat victories in the air ... it was a record for the unit, not the individual.

Not saying Wildcat is wrong or his source is, I'm just wondering where the numbers came from ... for BOTH sets of numbers. not just one.

My understanding is that the writers of "Eagles of the Southern sky" compared Japanese docus/official histories with Allied docus and the confirmed means Tainan victories that can be verified by US docus. I haven't see the book but that's what I have heard. Note that JoeB's figure is that of shorter timeframe.

Juha

oldcrowcv63 · Apr 14, 2014

tomo pauk said:
Re. bolded part: the experiments with turbocharger were undertaken in the USA from early 1930s, contrary to the experiments with 2-stage superchargers. After all, turbo-equipped engine was a 2-stage engine. For the mechanically driven 2-stage S/C for the V-1710, the USAC/USAF will need to 1st show some love (=money, resources) to the Allison - they were burning the midnight oil just to get the single stage V-1710 in order, to have something to power an new generation of fighters. The 2-stage R-1830 was tested on some aircraft competing for the orders the P-40 eventually won, due to it's still single stage engine.
The unfortunate decisions to install turbo darn close to the engine, like in the P-37 and P-39*, and unlike in the P-43 (that one, again unfortunately, got he wrong engine in the nose) hampered reliability and grow potential of a single-engined fighter with V-1710 in the nose.
No fighter is going to do much good if the competent radar and command network is not supporting it. As atested by Japanese once the Allies started striking back. The waves made in the SoPAC sounded something like this: send more P-38s. They also got P-47s in mid 1943. Both turbo-outfitted A/C.

*no, the XP-39 (with turbo) was not good for 390 mph right from the box, despite being unarmed

In this particular case it was just "send some P-38s" fifteen of which finally arrived about 3 months later (~November 1942).

Based upon earlier similar discussion in other threads, it seems the alternate option to develop and/or install a Single Stage, Two Speed Super Charger was not pursued because that would have necessarily meant sacrificing some of the Allison 1710's low altitude performance to gain a marginal improvement in performance at a slightly higher altitude.

eWildcat · Apr 14, 2014

gjs238 said:
Sounds like someone is trying to dogfight A6M's and Ki-43's.

I guess they didn't even have to try to dogfight to get into trouble : when your plane does nothing better than the enemy plane, except perhaps rolling at some speeds, you're bound to having a quite hard time.
Considering the very poor high altitude performance of the P-39, the pilots weren't even sure they could use the big help provided by radar stations so as to ambush the enemy from above.

gjs238 · Apr 14, 2014

eWildcat said:
I guess they didn't even have to try to dogfight to get into trouble : when your plane does nothing better than the enemy plane, except perhaps rolling at some speeds, you're bound to having a quite hard time.
Considering the very poor high altitude performance of the P-39, the pilots weren't even sure they could use the big help provided by radar stations so as to ambush the enemy from above.

Yes, but then how does one explain the success of the AVG with P-40's?

FLYBOYJ · Apr 14, 2014

gjs238 said:
Yes, but then how does one explain the success of the AVG with P-40's?

Tactics, tactics, tactics...

oldcrowcv63 · Apr 14, 2014

FLYBOYJ said:
Tactics, tactics, tactics...

Also, (and of course, in discussing the AVG, I am assuming we aren't talking about P-40s vs Zeros here) not all P-40s were the same. The P-40B/C initially delivered to the AVG was a bit lighter with somewhat better high altitude performance than many of those P-40Es employed in the PI, and later over Java, Australia and New Guinea. I don't know what weight saving measures might be implemented to improve the performance of the P-39/P-400 but my guess is that these were more limited than measures used to reduce the weight of the P-40E that appear to have been regularly if not universally adopted by the USAAF and RAAF.

FLYBOYJ · Apr 14, 2014

oldcrowcv63 said:
Also, (and of course, in discussing the AVG, I am assuming we aren't talking about P-40s vs Zeros here) not all P-40s were the same. The P-40B/C initially delivered to the AVG was a bit lighter with somewhat better high altitude performance than many of those P-40Es employed in the PI, and later over Java, Australia and New Guinea. I don't know what weight saving measures might be implemented to improve the performance of the P-39/P-400 but my guess is that these were more limited than measures used to reduce the weight of the P-40E that appear to have been regularly if not universally adopted by the USAAF and RAAF.

I don't think that would have made much of a difference, especially if you slowed one down to 180 knots and tied to "dance" with a Nate or Oscar. Bottom line, the AVG had it figured out and their combat record showed it.

oldcrowcv63 · Apr 14, 2014

FLYBOYJ said:
I don't think that would have made much of a difference, especially if you slowed one down to 180 knots and tied to "dance" with a Nate or Oscar. Bottom line, the AVG had it figured out and their combat record showed it.

I absolutely agree that tactics were the primary advantage and even a fully loaded P-40E with the right tactics was a better bet than a better performing aircraft without.

oldcrowcv63 · Apr 14, 2014

of course even a marginal improvement in performance may provide an increase in tactical options as well as improve survival or victory probability in a fight. Else why would the experienced pilots implement such weight reduction measures?

eWildcat · Apr 14, 2014

gjs238 said:
Yes, but then how does one explain the success of the AVG with P-40's?

What was said : tactics, clever use of a net of observers by Chennault, lighter P-40s which could fly a bit higher than their opponents if warned soon enough. Add to this Japanese aircraft that often flew lower than what happened at Guadalcanal, a higher proportion of Ki-27s instead of the better Ki-43s and A6Ms, and the possibility to retreat to another airfield when things got too bad (or you wanted to cause some deception, something Chennault liked to do to compensate for inferior forces).

Another factor that may be overlooked is that the P-39s in 1942 had a lot of teething problems. It seems the P-40s were a lot more reliable.

tomo pauk · Apr 14, 2014

oldcrowcv63 said:
In this particular case it was just "send some P-38s" fifteen of which finally arrived about 3 months later (~November 1942).

Based upon earlier similar discussion in other threads, it seems the alternate option to develop and/or install a Single Stage, Two Speed Super Charger was not pursued because that would have necessarily meant sacrificing some of the Allison 1710's low altitude performance to gain a marginal improvement in performance at a slightly higher altitude.

The V-1710 already have had a single stage supercharger. Installing a two-speed gearing for the S/C would've improved the low altitude performance, especially the 15 minute rating (military power). The dedicated low-altitude V-1710-87, that was installed only in the A-36s, was good for 1325 HP at ~2500-3000 ft (no ram;military power), vs. ~1100 at same altitude for the V-1710-39 (installed on P-40D/E, Mustang I) and likes (V-1710-35 and -63, installed in P-39C/D/F/K/L).

The V-1710s that received increased supercharger speed through use of 9.60:1 gearing were the ones that offered better power at altitude, while sacrificing low alt power (under ~9500 ft, including take off power) against latest engines with 'old' supercharger gearing (8.80:1). The dedicated low-alt V-1710-87 have had S/C gearing of 7.84:1.

Two-speed superchargers offer a far better flexibility than single-speed ones. It was not pursued by Allison, despite a request by NAA for the P-51, since they already have had hands full with both designing and ramping up production of wide range of V-1710s. They were developing the fluid (hydraulic) coupling for auxiliary supercharger installed on 2-stage engines; the engine-stage still using single speed gearing. Fluid coupling, most widely used on Daimler-Benz engines, gives infinite number of supercharger gears.

muscogeemike · Apr 14, 2014

Now I'm not saying the P-39 was a great success in the Pacific, but it did shoot down more then a "couple" of Zeros (as well as other Jap planes). If nothing else it was all we had and, like the F4F, "held the line" until better aircraft became available (in fact the P-39 was still in Combat at the end of 1943 and used in the Recon role to Nov 1944). The stats show it held its own with at least a 1:1 kill ratio in that theater, and there were Aces who downed all their kills in the Airacobra.

When judging the plane we must examine the P-39's record with the Soviets. They had great success with the aircraft against the same German planes we faced over Europe, and they used it almost exclusively as an Air to Air fighter - not a "tank buster" as our history has told us for years. In fact the 37 mm cannon the plane carried was a pre war design and was not effective against the armor of most WWII tanks after 1941 (in fact no AP shells were ever supplied to the Soviets). Were they better pilots than ours? Of course not but the number of Germans shot down by them would seem to say we have miss-judged the P-39 some.

GregP · Apr 14, 2014

Having had several former ALlison employees and factory reps visit while I was at Joe Yancey's Allison shop, I can tell you what THEY said.

They universally said (not all there at the same time) that Allison was a relatively small shop and did not have the money to pursue developments the only real customer did not want to pay for. They offered a 2-stage supercharger to the USAAF and USN separately, and more than once. Most of the former employees said they offered it either two or three times, and were always told, "No thanks, what we really want is the delivery of the V-1710-XX's that are on order!"

They DID have 2 sizes of impeller, done on their own, but that is a relatively low-cost part development.

When the customer wants a -89, you deliver a -89, not an experimental 2-stage unit. That would be breach of contract.

When they needed to fix issues, they got paid for doing that since Allison had told the War Department before ever signing contracts that some development would be required along the way as operational issues came to light.

It is also my understanding that the War Materiel Board removed the turbochargers from the P-39 and P-40, due to scarcity of some metals. They "saved" the high-altitude boost for the bombers ... B-17's and B-24's, and only left them in the P-38 fighters, of which they didn't build all that many. The USAAF was informed of the WMB's decision and passed it along to the contractors, as they had no choice in the matter. The WMB dispersed piece parts as they saw fit.

varsity07840 · Apr 14, 2014

muscogeemike said:
Now I'm not saying the P-39 was a great success in the Pacific, but it did shoot down more then a "couple" of Zeros (as well as other Jap planes). If nothing else it was all we had and, like the F4F, "held the line" until better aircraft became available (in fact the P-39 was still in Combat at the end of 1943 and used in the Recon role to Nov 1944). The stats show it held its own with at least a 1:1 kill ratio in that theater, and there were Aces who downed all their kills in the Airacobra.

When judging the plane we must examine the P-39's record with the Soviets. They had great success with the aircraft against the same German planes we faced over Europe, and they used it almost exclusively as an Air to Air fighter - not a "tank buster" as our history has told us for years. In fact the 37 mm cannon the plane carried was a pre war design and was not effective against the armor of most WWII tanks after 1941 (in fact no AP shells were ever supplied to the Soviets). Were they better pilots than ours? Of course not but the number of Germans shot down by them would seem to say we have miss-judged the P-39 some.

My understanding is there is only one AAF pilot "credited" with 5 kills in a P-39. His name escapes me but I'm pretty sure he flew out of Guadalcanal. I don't think he survived.
Duane

parsifal · Apr 14, 2014

muscogeemike said:
Now I'm not saying the P-39 was a great success in the Pacific, but it did shoot down more then a "couple" of Zeros (as well as other Jap planes). If nothing else it was all we had and, like the F4F, "held the line" until better aircraft became available (in fact the P-39 was still in Combat at the end of 1943 and used in the Recon role to Nov 1944). The stats show it held its own with at least a 1:1 kill ratio in that theater, and there were Aces who downed all their kills in the Airacobra.

I think it was Grau Geist who posted some very intersting numbers as to what what types shot down how many Japanese aircraft. The figures are claims based, so it is virtually assured that they overstate the actual numbers of victories. GGs figures are based on the AAF own post war wash up reports. From memory, it credits the P-39 in th entire pacific with something like 240 air victories. In doing that, they lost something like 800 airframes.

So, the exchange rate is not 1:1. The numbers is what they is.

FLYBOYJ · Apr 14, 2014

varsity07840 said:
My understanding is there is only one AAF pilot "credited" with 5 kills in a P-39. His name escapes me but I'm pretty sure he flew out of Guadalcanal. I don't think he survived.
Duane

Lt. William Fiedler, he was killed when his P-39 was stuck by a P-38, I believe while on the ground.

parsifal said:
I think it was Grau Geist who posted some very intersting numbers as to what what types shot down how many Japanese aircraft. The figures are claims based, so it is virtually assured that they overstate the actual numbers of victories. GGs figures are based on the AAF own post war wash up reports. From memory, it credits the P-39 in the entire pacific with something like 240 air victories. In doing that, they lost something like 800 airframes.
So, the exchange rate is not 1:1. The numbers is what they is.

Those losses were from all causes?

muscogeemike · Apr 14, 2014

parsifal said:
I think it was Grau Geist who posted some very intersting numbers as to what what types shot down how many Japanese aircraft. The figures are claims based, so it is virtually assured that they overstate the actual numbers of victories. GGs figures are based on the AAF own post war wash up reports. From memory, it credits the P-39 in th entire pacific with something like 240 air victories. In doing that, they lost something like 800 airframes.

So, the exchange rate is not 1:1. The numbers is what they is.

If all aircraft are scored by total lost to all causes, as you are doing, then no aircraft has the ratio it is credited with.

I've read that the Fin's claim their version of the Buffalo has the highest kill to loss ratio of any WWII fighter! You are hard pressed to find any US or Brit pilot who will say good things about it.

Again I don't say the airplane was a great success in the Pacific but it did contribute, men fought in it, won some, lost some, and lived or died flying it.

And, still, the different opinions of the Soviet pilots and the Western Powers towards the plane must reflect something. Many of the highest scoring Soviet Aces got many of their kills in the P-39, and no Western pilot scored close to their highest.

michaelmaltby · Apr 14, 2014

"....Were they better pilots than ours? Of course not but the number of Germans shot down by them would seem to say we have miss-judged the P-39 some."

Not mis-judged, not fully appreciated how the Eastern Front low altitude arena played into the Airacobra's strengths .... plus pilots inclined to get dangerously close to their targets ... The P-39 was a perfect fit for the Soviets.

The P-39 a Zero Killer???

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