P-39 vs P-40

[Tzaw1]

Originally Posted by michaelmaltby

Why there is no mention of P-63's in L.L. documents?

P-63 is mentioned on page 7 of this document:
The National Archives | DocumentsOnline | Image Details

[claidemore]

Have been reading WARPLANES TO ALASKA by Blake W. Smith and found a couple interesting things. It was a Soviet, General L.G. Rudenko, who requested that all aircraft deliveries of the 4th Protocol of Lend-Lease (which included all P63s), be done by the Alaska-Siberia route, rather than through Iran. Had the Soviets wished to use P63s against Germany, it would have been much simpler to bring them in through Iran.
Also, a quote from page 197:

Aircraft production in the Soviet Ujnion had long since rebounded from th devastating losses suffered in the opening months of the war. Soviet aircraft factories were now in high gear turning out 42,000 airplanes of all types in 1944: a production rate that was fully capable of meeting at least the fighter requirements of the Red Air Force. Even so, the SPC requested continued fighter plane deliveries aimed at rebuilding and reequipping depleted fighter units in the Soviet Far East in anticipation of war against Japan. The majority of P-63 Kingcobras were diverted to this region.

[michaelmaltby]

Good catch, Claidemore

MM

[Shortround6]

Going by "Vee's for Victory" by Daniel Whitney there were several reasons for deleting the Turbo from the P-39. Not the least of which seems to be that with the original installation the Airplane couldn't come close to the performance estimites or guarantees. Bell was off by about 10% on the weight of the UNARMED plane and off by at least that much in the speed. The intercooler installation seems to have been really bad. It not only had high drag but didn't work very well. In the interest of light weight it had been kept small but the result was that it didn't cool the intake charge very well. While most American intercoolers tried to remove 50% of the heat of compression between the two stages the XP-39 was only managing about 25% during high speed flight and 12% during climb. This ment much more danger of detonation and ment that full power or boost could not be used thus limiting performance of the aircraft. NACA estimated after installing the XP-39 in their full sized windtunnel that a single stage "altitude rated" engine would provide about 30mph more speed than the turbo engine up to about 13-14,000ft. This is after NACA did a clean-up that added 40+mph to the speed of the plane. the Turbo version wasn't expected to show ANY advantage in speed until over 19,000ft had been reached. And it was still about 10mph below the Guarantee speed. Once the requirement changed from 400mph at 20,000ft to 400mph at 15,000 the turbo was really out of the running. The small size of the P-39 ment that installing a larger intercooler setup was almost out of the question.
Please remember that the Early P-38s used the leading edges of the outer wings as inter-coolers and that some models of the P-38 had difficulty in using full power because while these leading edge intercoolers worked well enough with 1150HP engines they were not big enough to handle the airflow of 1300-1425HP engines.

[fibus]

Yeager said he could beat anybody in a P 39 at 100 feet. But no one wanted to fight at that altitude.

winkle brown flew both the F 4f and the hurricane.
How did they compare?

[gjs238]

Originally Posted by Shortround6

Going by "Vee's for Victory" by Daniel Whitney there were several reasons for deleting the Turbo from the P-39. Not the least of which seems to be that with the original installation the Airplane couldn't come close to the performance estimites or guarantees. Bell was off by about 10% on the weight of the UNARMED plane and off by at least that much in the speed. The intercooler installation seems to have been really bad. It not only had high drag but didn't work very well. In the interest of light weight it had been kept small but the result was that it didn't cool the intake charge very well. While most American intercoolers tried to remove 50% of the heat of compression between the two stages the XP-39 was only managing about 25% during high speed flight and 12% during climb. This ment much more danger of detonation and ment that full power or boost could not be used thus limiting performance of the aircraft. NACA estimated after installing the XP-39 in their full sized windtunnel that a single stage "altitude rated" engine would provide about 30mph more speed than the turbo engine up to about 13-14,000ft. This is after NACA did a clean-up that added 40+mph to the speed of the plane. the Turbo version wasn't expected to show ANY advantage in speed until over 19,000ft had been reached. And it was still about 10mph below the Guarantee speed. Once the requirement changed from 400mph at 20,000ft to 400mph at 15,000 the turbo was really out of the running. The small size of the P-39 ment that installing a larger intercooler setup was almost out of the question.
Please remember that the Early P-38s used the leading edges of the outer wings as inter-coolers and that some models of the P-38 had difficulty in using full power because while these leading edge intercoolers worked well enough with 1150HP engines they were not big enough to handle the airflow of 1300-1425HP engines.

Excellent post - thank you.
This helps clear up lingering questions, and dispel much hearsay, about why the turbo was removed from the P-39.

Any insights on why, after these changes were made and the plane fielded, the P-39 was so hated by the Americans but loved by the Soviets?

As this post started, the P-39 & P-40 both had single-stage supercharged Allison V-1710's.
Did the P-39 really underperform compared to the P-39?