SHOULD the P39 have been able to handle the Zero? Was it training or performance?

[Shortround6]

Well, P-39 not-so-expert.
Make factual statements and I won't challenge them.

I read the chart, as you should have realized when I said it was for WEP ratings. Presenting it a 2nd time doesn't change that.

You can stand by your statement, the statement that the 9.60 engines made 100 more hp at ALL altitudes is still wrong.

The statement that the difference is about 100hp is correct. But it is a different statement and does not validate the first one.

 

[P-39 Expert]

The actual documents may have been mostly unavailable to the general public, but the data from them could most certainly be found in period books of the time. For instance, here is the performance figures for the P-39N that I gleaned from Combat Aircraft of the World (W.R. Taylor) which was published way back in 1969. See any similarities with your oft-quoted document?

View attachment 487468

Excellent question. All I'm saying is wwiiaircraftperformance puts all the information in one place where direct comparisons can easily be made. Your example shows the P-39N with a top speed of 399mph at 9700'. That one line description, while completely accurate, covers only the speed at one altitude, ceiling and no climb figures whatsoever. This would lead the normal observer to think that the P-39N was only a low altitude plane. With wwiiaircraft you can directly compare speed/climb at all altitudes for all the planes. See some of the charts I have supplied. Plus it lists the test criteria and dates. Beats hunting all over for the information. Hope this helps.

 

[Shortround6]

I would note that the change of engine in the P-39 was not really a great improvement,
It basically moved the critical altitude of the Allison engine from 12,000ft to 15,500 and gave it around 100hp more at the higher altitudes.

I would note that the Merlin XII engine used in the Spitfire MK II raised the point at which the Merlin made 1000-1030hp by several thousand feet and nobody really claims the SPitfire II was a big improvement over the Spitfire I.
The Spitfire V with the Merlin 45 moved the 6lb boost point up another several thousand feet.
The Hurricane II with the Merlin XX moved the 6lb boost point from 18,000ft on a MK I to over 23,000ft.

Moving the critical altitude of the engine by 3,500ft and still being in the mid teens in late 1942/early 43 is hardly world class.

 

[P-39 Expert]

LOL OK surfer boy!

So was the penciled in climb rate of the P-39N available like that from the website? Also, those climb rates given in the un-doctored chart that I provided were possible at normal safe power levels when using ADI so I'm am quite certain that an F6F-3 in service was capable of those numbers at those specific ratings. So again I ask you, do you have more than one official government document showing the remarkable performance of the P-39N that you are so proud of?

And there are many climb charts on the website for the F6F-3. Why only post this particular one? Oh I know, because it's the one displaying the poorest climb performance for the machine...

The site gives the official govt/military performance tests in print format with graphs on most of the planes. No climb graph for the P-39N but there is a speed graph. The tests in print format offer climb figures for all altitudes up to the absolute ceiling in 5000' increments. No trouble to transfer those numbers on top of the Hellcat climb graphs so they can be compared directly. Also the test in your un-doctored chart are testing non-standard parts (those water injection nozzles) late in the war. The additional Hellcat chart that I provided is from a normal production F6F3 and agrees with the other normal Hellcat charts there. You shouldn't compare a late war test of specialized equipment to a normal production plane.

 

[pbehn]

The two stage Merlin P-51 only saw combat from Dec '43. The Spitfire IX had the same Merlin engine as the P-51B but weighed 2500# less than a P-51D so its climb rate was absolutely amazing and significantly higher than any of these planes. Great plane if you wanted to go to Belgium and back.

The problem with being a single type fan boy is that when discussing other types you descend into clichés. The Spitfire was always short ranged compared to the Mustang and others but not in absolute terms. The Spitfire Mk IX eventually had a max internal fuel load of 114 imp gal (136 US)and a total maximum internal plus external of 284 imp. gal (341 US). Its day job was to stop people in Belgium and France going to UK and back, at any altitude from sea level to 43,000ft.

The still air range of the Mk XVI (mk IX with Packard Merlin) was 1200miles with a total fuel load of 255 gals.

 

[Peter Gunn]

Lots of dead electrons in here. Having gone through this thread again, I still don't think you understand how a supercharger works, I don't think you understand how range works for mission planning. You have steadfastly refused to understand how shit works when explained by some very knowledgeable folks. You realize that virtually everyone here knows who Buzz Wagner, George Welch et. al. were, what WEP and the little wire is, where to find info on wwiiaircraftperformance, none of this is groundbreaking stuff here.

You are and entitled to your opinion and you have tried to back up arguments with some facts but they have been constantly refuted and still the circle argument goes on. I'm beginning to find it laughable that apparently the AAF, RAF and virtually everyone else except the VVS ( for very good reasons stated by others ) were all stupid to pass on this amazing war winning plane.

If it was so hot, why wasn't it used for escort in the ETO by 8th FC? Why couldn't it intercept Japanese bombers over Guadalcanal ( when the F4F could )? Why did virtually EVERYONE dump it in favor of at least the P-40 ( if not something even better ) the first chance they had?

Eh, good luck, and as I said earlier, Peace Out.

 

[P-39 Expert]

I would note that the change of engine in the P-39 was not really a great improvement,
It basically moved the critical altitude of the Allison engine from 12,000ft to 15,500 and gave it around 100hp more at the higher altitudes.

I would note that the Merlin XII engine used in the Spitfire MK II raised the point at which the Merlin made 1000-1030hp by several thousand feet and nobody really claims the SPitfire II was a big improvement over the Spitfire I.
The Spitfire V with the Merlin 45 moved the 6lb boost point up another several thousand feet.
The Hurricane II with the Merlin XX moved the 6lb boost point from 18,000ft on a MK I to over 23,000ft.

Moving the critical altitude of the engine by 3,500ft and still being in the mid teens in late 1942/early 43 is hardly world class.

Couple of things, first we seem to get bogged down with engine to engine comparisons. We should be comparing the PLANES to each other. A Hellcat had a 2000HP engine and a P-39N had a 1200HP engine, yet their performance is very similar. Engine to engine comparisons are fun, but the plane performance is more important IMO.

The small critical altitude improvement of 3500' from the 8.8 engines to the 9.6 engines doesn't sound like much but it did result in an additional 100 horsepower (I think we agree on this now) and even that doesn't sound like much. But, that 100HP improved the speed of a P-39 by 20mph and improved climb by some 1000fpm. A worthy improvement if you ask me.

One last thing on the endurance and the 20 gallon Reserve for T/O & Climb to 5000'. That reserve was the simple method for the pilot to plan his mission. He could take the available fuel, deduct the reserve and then use the available GPH figures from the charts to compute endurance. It did take 35 gallons or so to climb to 25000' but one did not climb to that altitude over his base and then turn to head to the target. You deducted the reserve which got you to 5000' then continued climbing in the direction of the target at best climb speed of 170mph INDICATED. True airspeed at 170 indicated was 238mph TRUE airspeed at 20000'. So as you are climbing you are also moving toward the target at 238mph average. Say it takes about 10 minutes to climb from 5000' to 25000'. You are now at 25000' but you are also 40 miles closer to your target. If you are not climbing but are in level flight for 10 minutes you cover 47 miles (282mph for 10 min). The difference is only 7 miles. This method is what the pilot's manual told the pilot to use to compute endurance and it proved to be pretty accurate.

By the way, I'm not mad at anybody and really enjoying our discussions on old airplanes. I have started using smiley faces and doing my best not to sound like an a-hole when I post. If I have offended anybody then please accept my sincere apology. Thanks to everyone for their replies and comments.

 

[DarrenW]

Also the test in your un-doctored chart are testing non-standard parts (those water injection nozzles) late in the war.

The Hellcat achieved those rates nevertheless. And the report was finalized in 1945 but actual testing occurred from February 1944 onwards. Are you saying that the U.S. Navy wouldn't take full advantage of the findings in this test? You do know that there was still plenty of fighting left, or were the Japanese fully beaten by March 1944 too?



And part of my reason for presenting it was to show that there's all kind of data out there and you haven't seen or read it all. Your ONE document regarding the P-39N will never be enough, because as a researcher one must have multiple examples for which to draw accurate conclusions from. And besides this, you continually ignore the basic fact that the P-39N, in the ONE test report you have presented, wasn't meeting US Army operating requirements.

So for a third time, what are your thoughts on the usefulness of the P-39N in 1944? Could it really deliver the same usefulness as say a P-47D or P-38J/L? As you can see I'm leading up to something here....

 

[P-39 Expert]

Lots of dead electrons in here. Having gone through this thread again, I still don't think you understand how a supercharger works, I don't think you understand how range works for mission planning. You have steadfastly refused to understand how shit works when explained by some very knowledgeable folks. You realize that virtually everyone here knows who Buzz Wagner, George Welch et. al. were, what WEP and the little wire is, where to find info on wwiiaircraftperformance, none of this is groundbreaking stuff here.

You are and entitled to your opinion and you have tried to back up arguments with some facts but they have been constantly refuted and still the circle argument goes on. I'm beginning to find it laughable that apparently the AAF, RAF and virtually everyone else except the VVS ( for very good reasons stated by others ) were all stupid to pass on this amazing war winning plane.

If it was so hot, why wasn't it used for escort in the ETO by 8th FC? Why couldn't it intercept Japanese bombers over Guadalcanal ( when the F4F could )? Why did virtually EVERYONE dump it in favor of at least the P-40 ( if not something even better ) the first chance they had?

Eh, good luck, and as I said earlier, Peace Out.

Sorry I'm so stupid especially after all you guys have tried your best to help me. Sorry again for my posts quoting facts direct from government/military tests or the pilot manuals.

Why couldn't it intercept Japanese bombers over Guadalcanal when the F4F could? Gee, I don't know. Maybe the attached graph will help. The P-39K is the dotted line. 7650# with the older less powerful engine tested in May '42.

 

[DarrenW]

A Hellcat had a 2000HP engine and a P-39N had a 1200HP engine, yet their performance is very similar. Engine to engine comparisons are fun, but the plane performance is more important IMO.

Yes, we all get it that the P-39 was fast for the amount of power available. But it came at a huge price. It had many deficiencies that were basically non-existent in other US fighter aircraft of it's time. Lack of useful range and payload, light construction (compared to other US warplanes) which made it far more vulnerable to enemy fire, and substandard armor protection for both pilot and engine, just to name a few.

 

[Shortround6]

I get a bit suspicious when small changes in an aircraft make huge changes in performance.
I will even grant that the P-39N had 150-160hp more at the higher altitudes but the climb figures don't track well.

I will try to post the relevant figures later.

 

[Shortround6]

Yes, we all get it that the P-39 was fast for the amount of power available. But it came at a huge price. It had many deficiencies that were basically non-existent in other US fighter aircraft of it's time. Lack of useful range and payload, light construction (compared to other US warplanes) which made it far more vulnerable to enemy fire, and substandard armor protection for both pilot and engine, just to name a few.

Many accounts speak well of it's construction or protection or I am reading the wrong ones?
It did have a number of deficiencies which may have been hard to design out.
I would note that some of these were supposed to be fixed by the P-39E which changed to the P-76 and up to 4000 were order at one point before the whole thing was canceled in favor of the P-63.
The Bell engineers went through two almost total redesigns of the P-39 trying for something better which leaves one wondering how much improvement you can get from a relatively small change in the supercharger gear ratio??
No test results but something to think about.

 

[DarrenW]

Sorry I'm so stupid especially after all you guys have tried your best to help me.

You said it, we didn't.

 

[DarrenW]

Many accounts speak well of it's construction or protection or I am reading the wrong ones?

I'm referring to what I have read in America's Hundred Thousand and a few other places. I can take a look and post a few examples later. One that comes to mind is that the placement of the engine behind the pilot made it very vulnerable to enemy fire from the rear (which apparently the P-39 received a lot of ) but there are others. Let me take a look....

 

[CORSNING]

1943, sea level to 15000 ft: the best fighter?
POST #29
I posted this back in 1 October 2012. In the five and one half years (almost) I have
continued my research with the help of several others. I would like to point out that
range was not a big consideration in this post.
To answer the original question asked by P-39 expert...NO, in the Pacific theater
of Operation, the P-39 at no time could be considered to have 'handled' the Zero.
One of the A6M's greatest assets was its range, it could strike anywhere and at
any time. The P-39N with its internal fuel capacity allowing it a 360 ml. range just
was not enough to get the job completely done in the PTO.

 

[drgondog]

Can we please use the normal 120 gallon internal capacity? PLEASE. The 87 gallon capacity was at the request of the Russians and only used on some N and Qs. A SPITFIRE had more range than a P-39 with 87 gallons.

The 110 gallon drop tank was in extensive use with the 8th AF in England and in the Pacific.

The 110 gallon tank was used initially in late 1943 on P-47C/D C/L but AFAIK never on the P-39. First used on P-51B in May 1944.

I'm unaware that Bell added a tank pressurization capability such as slaving off exhaust or instrument vacuum pump. Did Bell modify the P-39 so that they could carry ANY tank above 20K? Do you have any source documentation of either a mission flown with 110 gallon tank or any mission flown above 20K w/75 gallon combat tank?

Please point to your sources.

 

[DarrenW]

Thanks to everyone for their replies and comments.

And I thank you. It's been entertaining to say the least. So are you ready to capitulate and admit that your hypothesis regarding the P-39N's worth was overstated or will you continue to drag this on and on with no end in sight?

 

[wuzak]

I get a bit suspicious when small changes in an aircraft make huge changes in performance.
I will even grant that the P-39N had 150-160hp more at the higher altitudes but the climb figures don't track well.

I will try to post the relevant figures later.

I too am suspicious when a 10% power increase gives nearly 50% increase in climb rate....

 

[pbehn]

I like the conclusions to the test on the P39, a bit odd for a single engine combat plane. combat

1. The P-39 should not be spun intentionally under any circumstances.

2. The P-39 should not be snap rolled as the roll usually ends in a spin.

3. The best spin recovery is to simultaneously apply opposite rudder and neutralize the stick.

4. Power should be cut immediately if a power on spin is entered.

5. Care must be excercised during the recovery to prevent an accelerated stall and re-enty into the spin.

6. The wing tip spin chute does not aid recovery of the P-39Q from a flat spin.



Reading the report, the pilot bailed out as a result of 6
www.wwiiaircraftperformance.org/P-39/P-39Q_Spin.pdf

 

[DarrenW]

There has been some discussion whether the P-39N tested on 17/Oct/1942 had the reduced fuel capacity or not. I apologize if this has been brought up already, but I found this information on Joe Baugher's website:

Bell P-39N Airacobra

After completion of the first 166 P-39Ns, the USAAF requested that four fuel cells be removed in order to reduce the internal fuel capacity from 120 to 87 US gallons, and so to reduce the maximum permissible gross weight from 9100 lbs to 8750 lbs. This kept weight down, but unfortunately it also restricted range. Therefore, kits were provided that allowed the four fuel cells to be refitted in the field.

The first 166 P-39Ns were fitted with an Aeroproducts propeller having a diameter of 10 feet 4 inches. Beginning with the 167th P-39N, the Aeroproducts propeller was enlarged to 11 feet 7 inches in diameter, an increase of six inches.

The 500 P-39Ns were followed by 900 P-39N-1s (Model 26C). These differed only in some minor internal changes which altered the location of the center of gravity.

From where I stand the tested aircraft would have had the reduced fuel load of 87 gallons, as it was a P-39N-1 and not an earlier P-39N (of which only the first 166 manufactured had 120 gallons of internal fuel). But I lost track if this factoid is actually relevant anymore....