XP-39 II - The Groundhog Day Thread

[XBe02Drvr]

The P-39, P-40 and F4F over the Solomons barely scraped over a 1 to 1 kill/ claim ratio.

Which we could afford and the Japanese could not. That our less experienced pilots in lower performing planes could manage that ratio against the experten of IJNAF is an amazing achievement itself.
Probably partly due to our "overweight" and overbuilt aircraft. They didn't call Grumman "the Iron Works" for nothing.

 

[GrauGeist]

Without the racks, the P-51B was probably faster, not slower. With racks on, the positions switched. P-51D used more streamlined racks, 4 mph cost vs. 12 mph on the B.

A quick overview from Joe Baugher:

Specification of P-51B-1-NA:
One 1620 hp Packard Merlin V-1650-3 twelve cylinder Vee liquid-cooled engine. Maximum speed was 388 mph at 5000 feet, 406 mph at 10,000 feet, 427 mph at 20,000 feet, 430 mph at 25,000 feet, 440 mph at 30,000 feet.
Range on internal fuel was 550 miles at 343 mph at 25,000 feet, 810 miles at 253 mph at 10,000 feet. With maximum external fuel, maximum range was 2200 miles at 244 mph.
An altitude of 5000 feet could be attained in 1.8 minutes, 10,000 feet in 3.6 minutes, 20,000 feet in 7 minutes.
Service ceiling was 42,000 feet.
Weights were 6840 lbs empty, 9200 lbs normal loaded, 11,200 lbs maximum loaded.
Wingspan was 37 feet 0 1/4 inches, length was 32 feet 3 inches, height 8 feet 8 inches, and wing area was 233 square feet.

Specification of P-51C-10-NT:
One 1695 hp Packard Merlin V-1650-7 twelve cylinder Vee liquid-cooled engine. Maximum speed was 395 mph at 5000 feet, 417 mph at 10,000 feet, 426 mph at 20,000 feet, 439 mph at 25,000 feet, 435 mph at 30,000 feet.
Range on internal fuel was 955 miles at 397 mph at 25,000 feet, 1300 miles at 260 mph at 10,000 feet. With maximum external fuel, maximum range was 2440 miles at 249 mph.
An altitude of 5000 feet could be attained in 1.6 minutes, 10,000 feet in 3.1 minutes, 20,000 feet in 6.9 minutes.
Service ceiling was 41,900 feet.
Weights were 6985 lbs empty, 9800 lbs normal loaded, 11,800 lbs maximum loaded.
Wingspan was 37 feet 0 1/4 inches, length was 32 feet 3 inches, height 8 feet 8 inches, and wing area was 233 square feet.

Specification of the P-51D-25-NA:
One 1695 hp Packard Merlin V-1650-7 twelve-cylinder Vee liquid-cooled engine.
Maximum speed: 395 mph at 5000 feet, 416 mph at 10,000 feet, 424 mph at 20,000 feet, 437 mph at 25,000 feet.
Range was 950 miles at 395 mph at 25,000 feet (clean), 2300 miles with maximum fuel (including drop tanks) of 489 US gallons under most economical cruise conditions. Initial climb rate was 3475 feet per minute. An altitude of 5000 feet could be reached in 1l7 minutes, 10,000 feet in 3.3 minutes, 20,000 feet in 7.3 minutes.
Service ceiling was 41,900 feet.
Weights were 7125 pounds empty, 10,100 pounds normal loaded, 12,100 pounds maximum.
Wingspan was 37 feet 0 1/4 inches, length was 32 feet 3 inches, height was 8 feet 8 inches, and wing area was 233 square feet.

 

[XBe02Drvr]

And the lack of a supercharger is another myth that has been perpetuated for 75 years.

C'mon, man, the guy was a maintenance officer. He wasn't that ignorant. All the engine types in question had integral gear driven superchargers built in. Part of the engine, in wrench twister jargon. None of these guys had probably ever seen an external extra stage supercharger like European engines had, so to them an outboard turbocharger was just "a supercharger". "Turbo" was understood. The fact that in our ex post facto concise semantics we misconstrue their words is our (the modern world's) fault, not theirs.

 

[Peter Gunn]

And nobody ever notes the attrition of the best Japanese pilots by the P-39, P-40 and F4F. The P-39 and P-40 were still the most numerous AAF fighters in NG until Sept '43. The newer AAF pilots were much better trained than the earlier pilots, and the Japanese replacements were much worse in their training. The P-38, Corsair and Hellcat pilots were facing declining competition.

I doubt very much any Allied pilot fighting the Japanese during the calendar years 1942 and 1943 would be very inclined to agree with you. A case could even be made for the first several months of 1944, but then again, it would only be pilots reports, not actual test data.

 

[DerAdlerIstGelandet]

I doubt very much any Allied pilot fighting the Japanese during the calendar years 1942 and 1943 would be very inclined to agree with you. A case could even be made for the first several months of 1944, but then again, it would only be pilots reports, not actual test data.

 

[GregP]

Hi Reluctant Poster.

Show me a list of vetted kills. The only ones I know of are the USAAF Report 85 and Naval Aviation Combat Statistics - World War II, and people fight over those.

So, we are left with claims only. I have zero confidence in someone who says they have the kill information unless they state: 1) exactly what IS a "kill" (widely differing opinions), 2) where did they get their kill numbers exactly and how? (who did the vetting? Is it "official" and recognized by anyone).

When I think about it, all I see to really use is acknowledged losses versus claims because claims is all we really have. I have a great file of German claims ... 68,000+ claims. I don't have and have not seen a list of vetted German victories. As far as I know, Hartmann is sill at 352 victories.

 

[P-39 Expert]

P-39 Expert,

I heard / noticed that as well. Not sure if the guy narrating the film is a pilot or not. Did you notice how he said the P-38 had a supercharger? I know of the supercharger myth surrounding these engines, but when he mentioned that the 38 had a supercharger, and the 39 did not, I assumed he meant turbo, or turbosupercharger for period speak.

"Testing was factual and comparable. Pilot reports were hearsay and opinion." P-39 Expert

This comment is astounding. If testing was so factual and comparable, why did it get repeated so often? Why were there so many comments about engines running rough, large sections of rebuilt aircraft, and no manual?

If pilot reports were hearsay, why did the guys who were running the war want them? So the first guy who reported a Me-262, or long nosed FW-190, or a Me-109 with a bigger spinner were all speaking hearsay? I fought a non-export version of another countries primary fighter. I was talked to before the fight by several different people, and after the fight I did a AAR (After Action Report) and received several phone calls plus more debriefings by Intel. I was only a 4 ship flight lead, not an IP / Test Pilot. I wonder why they (Intel) wanted my opinion / experience so badly.

You also mentioned Chuck Yeagers fondness of the P-39. Did he fly it only in training, where the CG was most likely as far forward as could be made for the safety of new / novice fighter pilots? Have you ever reached out to him to ask his opinion on whether it would have made him an ace like the P-51 did? Be careful, he doesn't tolerate what he deems silly questions very well.

You never replied to my earlier, rather long post (594) so I don't hold much hope here either but will say it regardless. There are aviation mechanics, pilots, engineers who are mechanics and pilots, all whose experience with aircraft, military and otherwise, is quite large. They have stated and made known their collective background, experience yet you don't believe or give them due credit.

I have to ask, what is your aviation / mechanical experience? Have you sat down with and discussed P-39s with the guys who flew it, or other fighters in WW2? Have you worked on / restored / raced any as members here have? Have you taken flight lessons? Or are you like the majority of us gleaning through piles of old information, often with contradictory "facts", trying to sort out what really happened and why? There is a blend of both on here, and you aren't giving ANY credit to the other group or anyone who doesn't agree with your assumptions. Be careful, that's not the way to gain credibility.

Cheers,
Biff

Biff,

Please accept my apology, I should never have said that pilot reports were heresay and opinion. But any report from an individual will contain some opinion.

I am neither a pilot, mechanic or engineer. I just like to read about history. I will be 70 in February and my Dad served in WWII, so that is my favorite period.

You are correct, I'm just gleaning through piles of old contradictory information trying to sort out what happened and why. I became more interested when M. Williams started publishing the actual performance reports in wwiiaircraftperformance.org. This information cleared up a lot of confusion for me, since most prior published information was very contradictory, meaning some of it was wrong.

I'm just expressing my opinions based on that newer information, and getting almost 100% pushback from everyone who would rather believe what they have heard for 75 years rather than newer factual information and recently released information from the fall of the Soviet Union.

I'm not worried about credibility, I know I don't have any. But I do have a lot of facts that nobody else wants to believe.

I always enjoy your posts and please feel free to contact me anytime.

Thanks.

 

[XBe02Drvr]

Are there any existing loss records of Japanese forces in New Guinea?

 

[P-39 Expert]

And a "pilot report" is not the same thing as a "hangar story" to impress the locals many years after active duty. Active-duty pilot reports are solicited to give other active-duty pilots an edge in combat. If they are "inflated" or false in any way, everyone will know when they try the suggested tactic(s) in the pilot report, so nobody gives false active-duty pilot reports, even the show-off guys.

On the other hand, very specific numbers recalled 50 years later are suspect since our memories are generally rose-colored. I'd not trust an old WWII pilot who thought the best climb speed for some fighter was some exact number, but I DO trust him when he says that he never reached his airplane's top speed on a combat mission unless he was in a dive, because who wants to run their engine at absolute full power when you are 500 miles from home over hostile territory with a currently-good-running engine? That's why I believe the old guys when they say combat speeds were in the 250 - 350 mph range unless the fight was a descending chase. When combat joined, they went to military power and mostly only used WEP if their life was in danger, not just to get an offensive kill. There were exceptions, but not very many after the crew chief reamed the pilot for breaking the throttle gate wire without a good reason. That sometimes meant an engine change for the crew, and they would not be happy about it.

Luckily, today's jets don't have quite the issue the WWII planes did. They routinely go into afterburner (and usually track hot temperature cycles) on takeoff, whereas NOBODY used (or uses) WEP for takeoff in a piston fighter. There might not be enough rudder or aileron to stay on the runway if they did. Of course, we also don't have 150 performance number fuel today, either, so nobody runs the old engines at what used to be WEP.

Agree with you about WEP. Your crew chief was not to happy to see that wire broken and would want to know why you abused HIS airplane. And it was for EMERGENCY only as using it risked engine damage or failure.

 

[DerAdlerIstGelandet]

P-39 Expert,

No one thinks you are dumb. No one thinks you don't have facts. We don't think you are putting it together right.

When you make comments such as saying mixture adjustment is simple, and that simply removing weight will make something better, and then completely blow off people with actual experience explaining how things in the real world work, you kind of lose them.

You are a valued member here, but maybe try listening a lil more...

 

[P-39 Expert]

Not in late 1942/ early 1943 and it depends where we are talking. Many seasoned JN pilots were lost at Midway and that attrition never fully recovered. JAAF pilots were a different story. The P-39, P-40 and F4F over the Solomons barely scraped over a 1 to 1 kill/ claim ratio. Once the P-38 came on scene scores jumped. This is well documented in the 39th and 80th FS histories as well as other units that gave up their P-39s for P-38s. With that said, the P-39 did serve a purpose, it did hold the line but we weren't going to win the war with a 1:1 kill ratio.

The early planes were attriting Japanese pilots, whether it be from combat losses, accidents, weather or mechanical problems. Not just victory claims. The Japanese lost those planes and pilots because of combat, if not actually from combat. And those losses were the best of the best, since their pilot training fell off as the war progresses and they didn't rotate their pilots back home to teach the trainees. The P-38, Corsair and Hellcat pilots had it easier because of the work done before they arrived.

I'm just saying that early work would have been a lot more productive if the P-39 was made lighter.

 

[P-39 Expert]

P-39 Expert,

No one thinks you are dumb. No one thinks you don't have facts. We don't think you are putting it together right.

When you make comments such as saying mixture adjustment is simple, and that simply removing weight will make something better, and then completely blow off people with actual experience explaining how things in the real world work, you kind of lose them.

You are a valued member here, but maybe try listening a lil more...

I have never blown off anyone on here, never told them they didn't know what they were talking about, and certainly never even mentioned the word stupid. I have always been as courteous as I possibly can to everybody on here that disagrees with me, which is everybody.

But how anyone can say that removing weight will not make an airplane perform better is someone I'm going to disagree with every time.

 

[XBe02Drvr]

I'm just saying that early work would have been a lot more productive if the P-39 was made lighter.

Nobody's quibbling with the idea that a lighter P39 would have performed better. The devil is in the details, and the real world impracticality of most of the solutions you suggest are what is generating the pushback. The personnel at Port Moresby and Milne Bay were stuck with playing the hand they were dealt, and from the perspective of 3/4 century later, I think we can say they played that hand as successfully as was possible under the circumstances.

 

[Dash119]

I have never blown off anyone on here, never told them they didn't know what they were talking about, and certainly never even mentioned the word stupid. I have always been as courteous as I possibly can to everybody on here that disagrees with me, which is everybody.

But how anyone can say that removing weight will not make an airplane perform better is someone I'm going to disagree with every time.

Like you, I am not an engineer, A&P or a pilot. I don't disagree with everything you say. I have not posted in this thread up until this point, as I didn't think I had anything to add.

Having said that, you are dealing with many knowledgable individuals here and yet you continue to use very simplistic language which continues to get you in trouble. So...

I think an Allison V-1710 weighs about 1400 lbs. dry. If I remove that weight from the P-39 I can state categorically that the airplane will not perform better...

So maybe going forward; "But how anyone can say that removing weight, while maintaining proper weight and balance, will not make an airplane perform better is someone I'm going to disagree with every time."

 

[FLYBOYJ]

The early planes were attriting Japanese pilots, whether it be from combat losses, accidents, weather or mechanical problems. Not just victory claims. The Japanese lost those planes and pilots because of combat, if not actually from combat. And those losses were the best of the best, since their pilot training fell off as the war progresses and they didn't rotate their pilots back home to teach the trainees. The P-38, Corsair and Hellcat pilots had it easier because of the work done before they arrived.

I'm just saying that early work would have been a lot more productive if the P-39 was made lighter.

You're making a generalization that spans about 8 months, in some cases I can agree, but in other areas no. Again, the JAAF did not lose it's best pilots during the first 6 months and there plenty of them still around when better aircraft showed up.

 

[XBe02Drvr]

I think an Allison V-1710 weighs about 1400 lbs. dry. If I remove that weight from the P-39 I can state categorically that the airplane will not perform better...

So maybe going forward; "But how anyone can say that removing weight, while maintaining proper weight and balance, will not make an airplane perform better is someone I'm going to disagree with every time.

How you going to define "performance"; miles/hour, ft/min, degrees/sec, OR total losses during a period of combat ops (including operational) vs VERIFIED enemy combat losses?
Quite likely that which you sacrifice in pursuit of weight reduction will negatively effect your victory/loss ratio. (IFF, protection, firepower, etc) It's not just an airplane, it's a weapons system.

 

[FLYBOYJ]

So maybe going forward; "But how anyone can say that removing weight, while maintaining proper weight and balance, will not make an airplane perform better is someone I'm going to disagree with every time.

And this statement is about 98/99% correct. Depending WHERE in the weight and balance envelope the aircraft falls will also be a determining factor. Tail heavy aircraft (within the envelope) will generally fly faster but be less stable, nose heavy aircraft (within the envelope) may be a little more stable, require more elevator back pressure to maintain level flight (to be trimmed out) but may not gain maximum lift efficiency (slower flight at a given power setting). Removing weight will of course make the aircraft lighter (and will more than likely make the aircraft perform better) but you also have to consider WHERE you are removing that weight from, thus this IS NOT a linear calculation and I think GregP even gave the correct equation to figure this out about 100 posts ago!

PS - I actually witnessed this when I crewed a Jet at Reno. In once case the weight removed didn't make a difference until we got the C/G aft and then we saw results.

 

[DerAdlerIstGelandet]

I have never blown off anyone on here, never told them they didn't know what they were talking about, and certainly never even mentioned the word stupid. I have always been as courteous as I possibly can to everybody on here that disagrees with me, which is everybody.

But how anyone can say that removing weight will not make an airplane perform better is someone I'm going to disagree with every time.

I think you are not listening. People are telling you that you can't just remove the weight and it will magically get better. Removing weight also affects things such as CG. Depending on where that CG now lies will effect how it performs as well. Thats a real simple view of it. There is much more to it than that. Engineers sit down, perform calculations, and together with test pilots figure it out. You cannot simply modify an aircraft and think it will make it better. Trust me I have done countless modifications, and currently work in retrofit and modification engineering. This stuff has to be carefully evaluated.

Nobody's quibbling with the idea that a lighter P39 would have performed better. The devil is in the details, and the real world impracticality of most of the solutions you suggest are what is generating the pushback. The personnel at Port Moresby and Milne Bay were stuck with playing the hand they were dealt, and from the perspective of 3/4 century later, I think we can say they played that hand as successfully as was possible under the circumstances.

Thank you. Said much better than I have.

And this statement is about 98/99% correct. Depending WHERE in the weight and balance envelope the aircraft falls will also be a determining factor. Tail heavy aircraft (within the envelope) will generally fly faster but be less stable, nose heavy aircraft (within the envelope) may be a little more stable, require more elevator back pressure to maintain level flight (to be trimmed out) but may not gain maximum lift efficiency (slower flight at a given power setting). Removing weight will of course make the aircraft lighter (and will more than likely make the aircraft perform better) but you also have to consider WHERE you are removing that weight from, thus this IS NOT a linear calculation and I think GregP even gave the correct equation to figure this out about 100 posts ago!

PS - I actually witnessed this when I crewed a Jet at Reno. In once case the weight removed didn't make a difference until we got the C/G aft and then we saw results.

And this as well.

Again no one is saying reducing weight will not improve performance. But has to be done correctly.

 

[davparlr]

It is my understanding that American aircraft were designed to higher stress standards than the British so that for a similar size aircraft the American craft would be heavier. I also understand that part of the lightening of the P-51H was designing to the lighter standards which worked quite well. However to do so was a major impact and the P-51H is a significantly different aircraft than the P-51D. I do wonder if the P-39 was originally designed to the lighter British standards, how would it have performed.

 

[SaparotRob]

It is my understanding that American aircraft were designed to higher stress standards than the British so that for a similar size aircraft the American craft would be heavier. I also understand that part of the lightening of the P-51H was designing to the lighter standards which worked quite well. However to do so was a major impact and the P-51H is a significantly different aircraft than the P-51D. I do wonder if the P-39 was originally designed to the lighter British standards, how would it have performed.

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