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

[parsifal]

And, due to lack of effective warning, the P-39s mostly entered combat with an altitude and speed disadvantage (bounced from 6 o'clock high while in an intercept climb), not the best scenario to display the Airacobra's stronger points. Ask Biff what that means in a lackluster mount. An Eagle surprising a Phantom, maybe?
Cheers,
Wes

The defences at Moresby certainly had some problems with the shadow effect of the owen Stanleys, however ways were found to over come this problem. Most American sources claim there was no radar at Moresby until very late in the year, but in fact radar had been deployed from the beginning of march. it was not very effective at the beginning, but did improve.

The p-39s did receive advanced warning, usually from 'coast watchers" embedded in the known approach route s from lae to Moresby. Generally, even with plenty of warning they were still ineffective.

The Japanese never had any radar at Lae, and nothing to compare in terms of the ground based observers. The allies got quite good at exploiting this , using their level bombers to pound the airstrip from very low altitude approaches . Quite a number of Zekes were lost in landing/take off accidents because of this .

P-39s acted basically as targets for the Japanese to shoot at whilst other elements of the Allied arsenal did the real heavy lifting

 

[CORSNING]

P-39s acted basically as targets for the Japanese to shoot at whilst other elements of the Allied arsenal did the real heavy lifting[/QUOTE]

Parsifal, please tell me you did not say that. The P-39 especially after the "N" was nobody's fool
under 5,000 m. IN 1943,

 

[parsifal]

Elsewhere perhaps, but not over Moresby.

 

[XBe02Drvr]

Even so, it was no slouch. It just could not
go up high where all the other AF fighters designated for such could.

Those impressive P-39 numbers were for the N model, too late for New Guinea, and had more horsepower and and less weight than the early models in Moresby. Apples and oranges. If they had been available for early days things might have been a bit different.
Cheers,
Wes

 

[XBe02Drvr]

Your kidding me right?......lol Why do you think the russians liked them so much.......

Their theater was tailor made for the later N and Q P-39s, fast movers in the weeds, nice control at high speed and high "G" once the CG issues were fixed, and a flying arsenal to boot. And a tough, abuse-tolerant motor with much longer TBO than indigenous Soviet engines.
Not relevant to the D model in New Guinea.
Cheers,
Wes

 

[Shortround6]

Some of those numbers look suspiciously high. Higher than the numbers shown in the tests at Spitfire performance?
And those number were done with planes that weighed less than they should have. The only way you get a P-39N down to 7300lbs is to fly with less than full internal tanks. For some weird reason even the test of the N seems to show abnormally high climb rates compared to the M and the Q, They changed reduction gears and props between the M and N and that might account for it? But then they mounted a single 50 cal under each wing and yanked the .30s and the climb fell back down to just about the level of the M. We are talking about a 400 fpm change in both directions at some altitudes.

 

[Stig1207]

It's also worth noting that the P-39 experience on the Eastern Front, is based on anecdotal evidence, aces scores and so forth. Has anyone actually seen any figures for claims or credits for the number of enemy aircraft shot down by Russian flown P-39s?

 

[Schweik]

Parsifal,
Ruffato uses the Kodochosho records of all IJN air units in the Southeast Area to make his assessments. He does not rely on just US and Australian wartime claims, but compares claims vs reported losses of both sides, giving a score of claims vs actual losses. You should read it. He's an Italian so has no iron in the fire.

Can you summarize some of his stats for 1942? By type etc.?

 

[fubar57]

Can you summarize some of his stats for 1942? By type etc.?

I'd like to know where to read it in its entirety.

 

[CORSNING]

Some of those numbers look suspiciously high. Higher than the numbers shown in the tests at Spitfire performance?
And those number were done with planes that weighed less than they should have. The only way you get a P-39N down to 7300lbs is to fly with less than full internal tanks. For some weird reason even the test of the N seems to show abnormally high climb rates compared to the M and the Q, They changed reduction gears and props between the M and N and that might account for it? But then they mounted a single 50 cal under each wing and yanked the .30s and the climb fell back down to just about the level of the M. We are talking about a 400 fpm change in both directions at some altitudes.

OK then, go to WWII Aircraft Performance
Now click on the P-39N-1 section that clearly states its ability to climb
initially at 7,301 lbs. at a rate of 3980 fpm. and 4360 fpm at 7,500 ft.

 

[KiwiBiggles]

OK then, go to WWII Aircraft Performance
Now click on the P-39N-1 section that clearly states its ability to climb
initially at 7,301 lbs. at a rate of 3980 fpm. and 4360 fpm at 7,500 ft.

You missed out the quote below the results table:

"Prestone temperature does not meet Air Corps requirements in climb"
​

I bet you could get even better climb results in other aircraft if you didn't mind heat-soaking your engine.

 

[Shortround6]

OK then, go to WWII Aircraft Performance
Now click on the P-39N-1 section that clearly states its ability to climb
initially at 7,301 lbs. at a rate of 3980 fpm. and 4360 fpm at 7,500 ft.

And yet we have the test of the P-39M with the same engine but different reduction gear and prop climbing hundreds of fps slower and not only a test of the P-39Q-5 (using the same engine and prop?) climbing hundreds of feet slower. We have a note that says the external guns on the XP-63 cost about 110fps in climb or about the smallest difference that could be measured and they didn't expect the change on the P-39Q to be much different.

we also have two charts
http://www.wwiiaircraftperformance.org/P-39/p-39q-25-1400.jpg
http://www.wwiiaircraftperformance.org/P-39/P-39Q-30-1400.jpg

That show later P-39Qs (same engine as the N) with two different props and without guns and weighing 7600lbs not getting over 3800fpm in climb when using WEP

Leaving us to wonder where did that P-39N-1 get that extra 400-500fpm of climb from?

I would also note that power available for maneuvering (maintaining speed in a Hi G turn) is going to be much closer to the climb power than the level speed power. By that I mean look at the chart for the P-39Q-25. at 10,000ft (3048 meters) half of the advantage (difference between WEP and military power) of of WEP goes away by slowing down from max level speed to climb speed. The P-39s ability to fight/maneuver at 5000 meters, even in the later versions against the 109 and 190 is a bit suspect. Do a firing pass yes, but any hard maneuvering is going to result in either a slow airplane or the loss of thousands of feet of height.

 

[Schweik]

They could have easily tested it with 30 or 40 gallons less fuel or just removed wing guns or the internal starter or something.

 

[Greg Boeser]

I'd like to know where to read it in its entirety.

Try here:
Eagles of the Southern Sky

 

[fubar57]

Many thanks Greg

 

[Glider]

I always thought that one of the differences between the P39N and others was a significantly reduced fuel load, by about a third or am I wrong on this?
I mention this as I don't recall seeing a successful fighter having its fuel load reduced, added certainly, but not reduced

 

[Greg Boeser]

Depends what you are after. Later P-39 makes a great point defense fighter. Not a very good long range escort. By 1943 the western allies were on the offensive, pushing the German defenses back. No place for a short-legged fighter to shine.

 

[XBe02Drvr]

The P-39s ability to fight/maneuver at 5000 meters, even in the later versions against the 109 and 190 is a bit suspect.

What do you expect? The Cobra's forte was speed in the weeds and 16,000 feet was in the upper limits of its combat performance envelope. So what? That wasn't where the action was. Dogfighting at 15-16K wasn't going to keep the Stukas off the troops.

Leaving us to wonder where did that P-39N-1 get that extra 400-500fpm of climb from?

Judging from the footnotes pointed out above, I would guess it came from reduced fuel load and cooking the engine to get flashier numbers. Everything Larry Bell did seemed to smell of flash over substance.
Also bear in mind, early Ns had reduced fuel tankage per Soviet request, while later Ns and most all Ps and Qs went back to the larger capacity. And many were field modded to increase or decrease tankage.
Cheers,
Wes

 

[XBe02Drvr]

allies were on the offensive, pushing the German defenses back. No place for a short-legged fighter to shine.

Unless said fighter is providing low cover for advancing armor and mechanized infantry while operating from forward airstrips, Soviet style.
Cheers,
Wes

 

[XBe02Drvr]

Later P-39 makes a great point defense fighter.

Even the hottest early N models with the reduced fuel would have been a nonstarter at ETO altitudes against escorts with two speed or two stage superchargers or turbos.
Cheers,
Wes