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

[drgondog]

True but a.) weighed 400 pounds more and b.) needed twice the radiator surface area to cool it.

Can we whisper 'unrecoverable aft cg issues' after ammo gone?

 

[bobbysocks]

"she'll tumble and spin and soon auger in
give me a P39"

and dont forget the lovely aroma of exhaust and cordite in the cockpit....

 

[michaelmaltby]

".. Chuck is often quoted as being willing to soldier on in the P-39 - but he didn't mean it for ETO. He would have had his ass handed to him by perhaps inferior pilots had they flown to 109 and 190 strengths rather than try low altitude turning fight. Escorting B-17s at 25000 feet would have resulted in extremely high losses. The Brits figured that out in 1941 and sent all of theirs to USSR."

All granted ....

 

[bobbysocks]

as much as chuck liked it....William "Obee" O'Brien who was in his FG had a slightly different opinion:

HOW WAS FLYING THE P-39?

I could write a book about this, but thank God someone else did. The book is "Nanette" by a man named Park. He, like me, thinks the damn thing had a soul. The P-39 was undoubtedly the worst airplane the Air Corps had in its inventory. But if a pilot could accumulate about 150 hours, he should be awarded a medal, as he is well on his way to being a fighter pilot. That particular airplane was absolutely unforgiving and aerodynamically unstable. It was so bad that many service pilots did not, or more likely, would not fly it. Tactical units had members sent to the manufacturers to fly P-39s to their units. I know this because I was one of the lucky ones who got to do this type of work.

357th FG Interview

here's a story of Bill Overstreet's experience in a 39 from joey maddox's book the great rat race...go up to page 116.

http://books.google.com/books?id=1f...wBw#v=onepage&q=357th Fg P 39 stories&f=false

 

[davebender]

Did P-63 clean up the aerodynamics in addition to providing a better engine?

 

[Jabberwocky]

".. Only the P-38 and P-63 survived the war with Allisons as the powerplant of choice for US Fighters."

And the Twin Mustang ...

The Merlin was the powerplant of choice for the Twin Mustang. The switch to Allisons was forced by Rolls-Royce insisting that once the war ended their royalty payments be resumed.

 

[drgondog]

The Merlin was the powerplant of choice for the Twin Mustang. The switch to Allisons was forced by Rolls-Royce insisting that once the war ended their royalty payments be resumed.

The Air Force was delighted to pay royalties for a better engine. NAA Hated the ALLIson and Schmeud was bitter till his dying day that the Sec'y of the Air Force forced the Allisons onto the P-82E in order to get the contract.

 

[wuzak]

Major CG issues re-locating 1600 pounds from behind cockpit to in front. Total re-design almost with no common parts.

Why was the P-39 so zippy at low altitudes on limited power?

Because it was small

Why didn't they fit bigger superchargers, inter-coolers and larger engines in the P-39?

Because it was small

Simple really.

To be fair, there were Merlins that were roughly sized as P-39's V-1710 (complete with supercharger), and required no inter-coolers. Made in the USA, never the less.

True but a.) weighed 400 pounds more and b.) needed twice the radiator surface area to cool it.

Can we whisper 'unrecoverable aft cg issues' after ammo gone?

I think what Tomo suggests is the V-1650-1. Sure it doesn't have the altitude performance of the 60-series, but it does have much better altitude performance than the V-1710 in the P-39.

It is also only about 100lbs heavier and doesn't need that much more cooling, if any. Certainly doesn't need an intercooler and associated radiator.

The V-1650-1 was significantly shorter than the two stage versions, and should be shorter than the V-1710. So that may help in balancing the CoG issues.

 

[wuzak]

"... Neutered how?

And if not neutered when would it have entered large scale squadron service?"

The USAAF had no engagements that in any way replicated the totality of the Eastern Front where the Soviets were able to utilize the P-39 as an under 11,000 ' down to the deck dogfighter, supporting Sturmoviks .... but, that said, during Guadalcanal, the P-39 was an effective fire support platform over land and sea. The 20 mm canon from the British rejects and later the 37 mm Olds canon, were good at barge busting. The AC was less vulnerable to ground fire than the P-40 due to the engine location. Range wa less an issue in this theatre, and the idea of accepting that the P-39 was not ever going to be a high altitude interceptor and hence getting on with using the AC for its strengths, seems obvious to me. It was a flawed concept in 1941-42 but by 1944 the Q model was very good and the P-63 took the best and made it better. The Soviets certainly benefitted, and those American who mastered the P-39, like Chuck Yeager, knew it had sass.

MM

Some would say that the removal of the turbo after the XP-39 would count as "neutering".

 

[Shortround6]

Well, considering that the original turbo installation didn't work for sour apples and after the NACA issued a report AFTER testing it in a full sized wind tunnel that offered little hope of it EVER reaching the predicted performance one wonders how it was "Neutered".

There were 939 P-39s delivered by the end of 1941, if they had waited to solve the turbo problems (if they could be fixed) how many hundreds of fewer P-39s would have been available in the spring/summer of 1942?

AS near as can be figured out the CLAIMED 390mph at 20,000ft and fast climb were not only never achieved but never attempted. Not only were there chronic cooling problems with the XP-39 but there was a problem with the original drive shaft and the early flights were restricted to 2600 engine RPM, not the full 3000rpm until AFTER the plane came back from the wind tunnel.

Can you neuter something that was impotent to begin with?

 

[wuzak]

Well, considering that the original turbo installation didn't work for sour apples and after the NACA issued a report AFTER testing it in a full sized wind tunnel that offered little hope of it EVER reaching the predicted performance one wonders how it was "Neutered".

There were 939 P-39s delivered by the end of 1941, if they had waited to solve the turbo problems (if they could be fixed) how many hundreds of fewer P-39s would have been available in the spring/summer of 1942?

AS near as can be figured out the CLAIMED 390mph at 20,000ft and fast climb were not only never achieved but never attempted. Not only were there chronic cooling problems with the XP-39 but there was a problem with the original drive shaft and the early flights were restricted to 2600 engine RPM, not the full 3000rpm until AFTER the plane came back from the wind tunnel.

Can you neuter something that was impotent to begin with?

I certainly wouldn't say the USAAF neutered the P-39. Just that I know some people would.

Was there ever any danger that Allison would develop a 2 speed drive for their supercharger or, considering how they went with the 2 stage design, a variable speed supercharger?

 

[CobberKane]

Oh boy, I can feel a new thread coming on. In fact I think I'll go back and post it myself...

 

[drgondog]

Wuzak - I was referring the the 1650-3 (and associated changes to cooling system) when i flipped out the 400 pound comment. IIRC it was closer to 350 for just the engine comparison...

As to cooling, the figure of 2x was extrapolated directly from the P-51A/Allison to P-51B/1650-3 experience encountered by NAA. In my mind I was being charitable as the P-39 was plagued by cooling issues in 1941-1942.

 

[wuzak]

Wuzak - I was referring the the 1650-3 (and associated changes to cooling system) when i flipped out the 400 pound comment. IIRC it was closer to 350 for just the engine comparison...

Of this I was aware.

The Merlin doesn't have to be the 1650-3. The V-1650-1 could give a useful altitude performance gain without much weight penalty, and it shouldn't require the massive increase in cooling capacity for the -3.

Though Packard didn't make them, I wonder how a Merlin 45 would have gone in the P-39. Obviously low down performance would suffer, but there should be some gain at higher altitudes (the 45 having a higher FTH than the Allison).

 

[Shortround6]

Actually not by that much once the later Allisons with 9.60 gears showed up. Critical height the Merlin 45 may be 3-4,000ft higher than a late model P-39 which would be a help but not solve the problem. The Late Allisons sort of split the difference between an early Allison and the Merlin 45.

A big problem is the weight, A P-39D clean is about 1000lbs heavier than a Spit V clean or almost 15%. Put together with the smaller wing and the wing loading was about 30% higher. At altitude the P-39 has to fly faster just to keep from stalling leaving that much less power for climb and maneuver.

Then you have a take-off problem. Early P-39s had 1150hp for take-off, late model Ds, Ks and Ls had 1325hp for take-off and the late versions had 1200hp for take-off. Merlin 45 had 1230hp for take-off at 12 lb boost. While the Allison was rated for 5 minutes CLIMBING at take-off or Military Power the Merlin was not so rated, what they did in the squadrons I don't know. We do know that Allisons tolerated over-boost abuse fairly well at low altitudes.

 

[krieghund]

This is taken from the NACA report about the P-39 with the turbo and a single stage blower. The single stage is better lower to the deck.

 

[krieghund]

and their Zeros have had two-speed superchargers

The first year of the war the P-39 was engaged against the A6M2 with the Sakae 12 engine which was single stage with a critical of about 14,600 feet, albeit about 2000 feet higher that the V1710-35.

 

[pinsog]

Ok. So the Zero has better performance up high than the P39, the Zero also had better performance than the F4F up high, in the middle and down low. At least the P39 had a significant advantage down low.

How did the P39's performance compare with the F4F up high?

 

[krieghund]

I guess about like this

 

[pinsog]

I guess about like this

Thank you for the graph.

This seems to show that the P39 will outperform the F4F up to 24,000 feet or so. I'm having a hard time believing that it was the P39's performance as much as it was a training issue considering the F4F was around 1 to 1 against the Zero. I think if I was given the choice, I would choose the P39, at least I had the option of running if things didn't work in my favor.