P39 performance per included test dated October 1941

pinsog · Apr 2, 2012

http://www.wwiiaircraftperformance.org/P-40/PHQ-M-19-1307-A.pdf

Was anybody else impressed or more appropriately, suprised, by the data in this particular test concerning the P39? The test states that the P39 is an even match for a Spitfire below 15,000 feet, not only out diving the Spitfire, but being faster, AND OUTCLIMBING THE SPITFIRE BELOW 15,000! I for one was flabbergasted when I read the test. Was anyone else?

Why, if in this test the P39 is a match for the Spitfire below 15,000 feet, does nearly everone shake their head in disbelief at the Soviets stating that the P39 was a match for a 109 or 190 up to 20,000 feet after the wing guns and some of the armor have been removed?

pbfoot · Apr 2, 2012

Not really . I wonder if that iis the test done at Rockliffe near Ottawa , after the test the RCAF wanted to put the P39 in production for itself
http://www.ww2aircraft.net/forum/aviation/canada-australia-what-would-you-build-32007.html

pinsog · Apr 2, 2012

I don't understand which side of the argument you are on. Do you agree with the report that the P39 was as good as the Spitfire below 15,000 feet. Or do you think the report is biased toward the American fighters?

It doesn't look to me like the report is biased, especially when comparing the Hurricane to the P40. It also states that both British fighters turn better than any of their American counterparts. Seems to me like it is a reasonable test.

michaelmaltby · Apr 2, 2012

Chuck Yeager believed that no fighter could touch the P-39 at 600' ..... the success the Soviets had with the P-39 'system' (Bell-Lend-Lease Support) wasn't a fluke. At low altitudes and close firing range the P-39 was a match for the Me-109 and/or Fw-190. But it was best used fighting in the vertical plane -- 10,000 ' to ground level. [The P-63 KingCobra was a match for the P-51 on those same terms].

Politics was/is a factor in defense purchases - we all know that. Some USAAF 'people' didn't 'like' the P-39 - and let's face it - the P-39 wasn't what the RAF, RCAF or USAAF needed.

MM

Denniss · Apr 2, 2012

According to the document the P-39 was a P-39C. If we trust wiki or joe baugher's site the P-39C had neither armor nor self-sealing fuel tanks and had two machineguns less than a P-39D. The weight advantage was ~400 pounds compared to P-39D.

There seem to be several transcription errors in this document, sometimes P-39 is written instead of P-38 or P-39D instead of P-39C and vice versa.

pbfoot · Apr 2, 2012

Ilike the P39 it was in maybe alittle advanced for its time ,

pbfoot · Apr 2, 2012

Denniss said:
According to the document the P-39 was a P-39C. If we trust wiki or joe baugher's site the P-39C had neither armor nor self-sealing fuel tanks and had two machineguns less than a P-39D. The weight advantage was ~400 pounds compared to P-39D.

There seem to be several transcription errors in this document, sometimes P-39 is written instead of P-38 or P-39D instead of P-39C and vice versa.

You can't trust these documents , it doesn't indicate who flew them or anything .I've read an article where a 2 RCAF pilots was showing evryone the capability of 109's and when one pilot flew against p38's he'd let them win because it was benificial when it came time to hit the bar/px . So some where out there is a document/report stating the the 109 was a dog

pinsog · Apr 2, 2012

pbfoot said:
You can't trust these documents , it doesn't indicate who flew them or anything .I've read an article where a 2 RCAF pilots was showing evryone the capability of 109's and when one pilot flew against p38's he'd let them win because it was benificial when it came time to hit the bar/px . So some where out there is a document/report stating the the 109 was a dog

I can't imagine, under wartime conditions, the test pilots noit showing the new guy exactly what they were up against. It just seems like a really bad idea. Shouldnt they be teaching them the best way to beat a 109 instead of thinking "how can I get the most beer bought for me when I land"

GregP · Apr 2, 2012

The P-63 was a match for a Mustang at ANY altitude. Though slower by 27 mph or so, it had a higher service celiing, a better roll rate, and was a very good fighter not used much by the USAAF.

Jenisch · Apr 3, 2012

Why the Soviets were not allowed to use the P-63 against Germany?

wuzak · Apr 3, 2012

pinsog said:
Was anybody else impressed or more appropriately, suprised, by the data in this particular test concerning the P39? The test states that the P39 is an even match for a Spitfire below 15,000 feet, not only out diving the Spitfire, but being faster, AND OUTCLIMBING THE SPITFIRE BELOW 15,000! I for one was flabbergasted when I read the test. Was anyone else?

I imagine it would be because the Spitfire used for comparison used a single speed single stage Merlin with a higher rated altitude than the Allison in the P-39, giving better altitude performance at the expense of low altitude performance.

Thoughts?

Jabberwocky · Apr 3, 2012

I wonder what Spitfire and Hurricanes were tested? There is no indication to sub-types in the documentation.

AFAIK, the US had access to a Spitfire Mk I and two Spitfire Mk VA that they'd used for testing. The Mk Vs arrived in April 1941.

Anyone know what Hurricanes were flying in the US in 1941?

Juha · Apr 3, 2012

pinsog said:
http://www.wwiiaircraftperformance.org/P-40/PHQ-M-19-1307-A.pdf

Was anybody else impressed or more appropriately, suprised, by the data in this particular test concerning the P39? The test states that the P39 is an even match for a Spitfire below 15,000 feet, not only out diving the Spitfire, but being faster, AND OUTCLIMBING THE SPITFIRE BELOW 15,000! I for one was flabbergasted when I read the test. Was anyone else?

Why, if in this test the P39 is a match for the Spitfire below 15,000 feet, does nearly everone shake their head in disbelief at the Soviets stating that the P39 was a match for a 109 or 190 up to 20,000 feet after the wing guns and some of the armor have been removed?

I'm not the least surprised because already in Air Enthusiast (later Air International) Aug 1971 there was an article on P-39 which gave an abstract on British AFDU tests in late summer 41 Airacobra Mk I vs Spit Mk VB and 109E which noted that "although the Airacobra has superiority of speed up to 15,000 ft, it was outclimbed and just out-turned by the Spitfire" The abstract is appr 3/4 page long, so that was only a small part of it. When taking in notice the fact that -39C was appr 425lb lighter than -39D and US Spit might well have been a bit wearier than that used by AFDU the US test results were not very surprising.

Juha

Jabberwocky · Apr 3, 2012

All quotes are taken from Joe Baugher's excellent website: Airacobra I for RAF, P-400

The Air Fighting Development Unit received a British Airacobra I on July 30. They subjected it to tests and completed their report on September 22. They found the aircraft to be pleasant to fly and easy to takeoff and land. Controls were well balanced and although heavier than those of the Spitfire at normal speeds, did not increase appreciably in weight at high speeds as they did in the Spitfire.

A&AEE found that the Airacobra's controls were "light in normal flight but become heavy in the dive at speeds in excess of 3000 mph ASI. They are comparable with the fabric covered ailerons on a Spitfire Mk I"

Interesting difference between the A&AEE and the AFDU - ailerons starting to get out of alignment maybe? Spitfire were quite prone to aileron imbalance slowing roll rate.

It was difficult to hold the aircraft in a dive at high speeds unless the aircraft was trimmed nose-heavy. During a turn, the Airacobra would give ample warning of a high-speed stall by severe vibration of the whole airframe. Handling in formation and formation attacks was good, although deceleration was poor because of the plane's aerodynamic cleanliness. Take-offs and landings in close formation were not considered safe, since there was considerable difficulty in bringing the aircraft back to its original path after a swing.

In the US combat trials found that the P-39C gave "very little warning is given before the airplane makes a complete half snap roll".

Again, interesting inconsistency between the different tests.

The Airacobra I was powered by an Allison V-1710-E4 twelve-cylinder V in-line engine rated at 1150 hp for takeoff. Weights were 5462 pounds empty and 7845 pounds normal gross. Maximum speeds were 326 mph at 6000 feet, 343 mph at 10,000 feet, 355 mph at 13, 000 feet, 341 mph at 20,000 feet. Initial climb rate was 2040 feet per minute. With an internal fuel capacity of 100 Imp gal the Airacobra had an endurance of 1 hour 20 minutes at maximum continuous cruising speed at 6000 feet, 1 hour 5 minutes at 12,000 feet, and 1 hour 35 minutes at 20,000 feet. The true airspeeds at these altitudes were 287 mph, 327 mph, and 308 mph, respectively. Under most economical cruise conditions, the endurance increased to 3 hours 20 minutes, the relevant speeds being 183 mph at 6000 feet, 217 mph at 12,000 feet, and 215 mph at 20,000 feet. Under maximum continuous climb conditions, it took 15 minutes to reach 20,000 feet. The operational ceiling was considered to be about 24,000 feet, although there was a marked decrease in performance above 20,000 feet. At the Airacobra's rated altitude of 13,000 feet, it was 18 mph faster than the Spitfire VB. However, the speed fell off rapidly above that height, and the two planes were almost exactly matched at 15,000 feet. At 20,000 feet, the Spitfire VB was 35 mph faster and at 24,000 feet it was 55 mph faster. The ground run of the Airacobra during takeoff was 2250 feet, as compared with 1470 feet for the Hurricane II and 1590 feet for the Spitfire V.

The AFDU also did some comparative dog-fighting tests with the Airacobra against a Spitfire VB and a captured Messerschmitt BF 109E. The Airacobra and the Bf 109E carried out mock dog-fighting at 6000 feet and 15,000 feet. The Bf 109E had a height advantage of 1000 feet in each case. The Bf 109, using the normal German fighter tactics of diving and zooming, could usually only get in a fleeting shot. The Bf 109 could not compete with the Airacobra in a turn, and if the Bf 109 were behind the Airacobra at the start, the latter could usually shake him off and get in a burst before two complete turns were completed. If the Bf 109 were to dive on the Airacobra from above and continue the dive down to ground level after a short burst of fire, it was found that the Airacobra could follow and catch up to the Bf 109 after a dive of over 4000 feet. When fighting the Bf 109E below 20,000 feet, the Airacobra was superior on the same level and in a dive.

A similar trial was carried out against a Spitfire V. Although the Airacobra was faster than the Spitfire up to 15,000 feet, it was outclimbed and out-turned by the Spitfire. Unless it had a height advantage, the Airacobra could not compete with the Spitfire. If on the same level or below, at heights up to about 15,000 feet, the Airacobra would have to rely on its superior level and diving speeds and its ability to take negative "G" without the engine cutting out. Above 15,000 feet, the Airacobra lost its advantage in level speed.

The Airacobra was considered to be very suitable for low altitude operations because of the excellent view and controllability, and it was fully maneuverable at speeds above 160 mph.

I think that the concentration on very high altitude fighting at the end of the BoB and beginning of 1941 had the RAF thinking that its fighters needed to be capable of combat at 25,000 ft plus.

If the Airacobra's ceiling was only 24,000 ft, and performance was lackluster at 20,000 ft, its understandable that the RAF preferred to leave the P-39 out of the ETO.

While combat altitudes came down lower for the RAF in 1942, I think its this lack of high-altitude performance that really prejudiced the RAF against the aircraft in 1941.

rank amateur · Apr 3, 2012

Jenisch said:
Why the Soviets were not allowed to use the P-63 against Germany?

As far as I know, the Sovjets got the bulk of all p-63's ever produced. If these never came to action against the Germans, I'd wager a guess that it was because the Sovjets didn't seem to need them. I have read somewhere they were held in reserve for an oncoming attack from the Japan. According to wiki a few flights secretely adopted the p63 against the germans. But wiki is notoriously unrealiable so I wouldn't bet money on it

pbfoot · Apr 3, 2012

Jabberwocky said:
I wonder what Spitfire and Hurricanes were tested? There is no indication to sub-types in the documentation.

AFAIK, the US had access to a Spitfire Mk I and two Spitfire Mk VA that they'd used for testing. The Mk Vs arrived in April 1941.

Anyone know what Hurricanes were flying in the US in 1941?

To me it would make sense that they would use the Canadian Built Hurricane

eagledad · Apr 3, 2012

Hello!

While I don't know what Hurricane was used, I would like to note that a Hurricane Mk IIA, Z2963 was tested by the NACA in Virginia from Nov 25 thru Dec 28 1941. One could speculate that Z2963 was the Hurricane used in the October test.

May God fly your wing!

Eagledad

michaelmaltby · Apr 3, 2012

"... I'd wager a guess that it was because the Sovjets didn't seem to need them. "

And I'd wager that you're correct. As 1944 wound down, increasing amounts of American aid to the Soviets was ear-marked for the Japanese front that Stalin had promised to open up during Yalta. This material was supplied from US Pacific ports directly to the Soviet pacific Port(s). I don't think the P-63 deployment is a big mystery -- the objective was to equip the Soviet offensive without withdrawing stores or manpower (engineering and medical personnel excepted).

MM

GregP · Apr 3, 2012

I can say with certainty that the P-63 flies very well according to at least three people I know who have flown the one at Palm Springs, California. It is powerful, clmbs, rolls, and turns well. Yest you think I forget it, of course they weren't in combat, but they compare it with the other warbirds they fly very well for power, speed, and handling. That says something even if the armament portion is missing.

I'm sure we've all seen the P-63 crash clip on Youtube. The pilot was flying at 40" manifold pressure. If he had been at 60" or 70" he would have climbed to 10,000 feet before running out of airspeed. All the warbirds pilots I know whowere there were just dumbfounded taht this could have happened since the maneuver wasn't in the practive, not expected in the show, and there was no indication whatsoever that the pilot would attempt a hammerhead or whatever he was doing when the accident happened.

tomo pauk · Apr 3, 2012

wuzak said:
I imagine it would be because the Spitfire used for comparison used a single speed single stage Merlin with a higher rated altitude than the Allison in the P-39, giving better altitude performance at the expense of low altitude performance.

Thoughts?

On the right track, I'd say.
The P-39C is barely available for 1941, unlike the Spit Mk.V; the self sealing tanks were present at Spit V, unlike the P-39C (Dennis is right; the installation of the SS tanks reduced the fuel tanksge from 170 US gals to 120, for P-39D). The comparison makes no sense IMO.
Come 1942, the P-39D has and engine with supercharger set to max out (for 1150 HP) at 12000 ft; the Merlin 45 outputs that kind of power at circa 17000-18000 ft (all values without ram effect). No wonder the climbing race from deck to 15000 ft is going to be won by P-39D. For a Spitfire V to beat the P-39 in that race, it needs to have low-level Merlin installed (Mk. 50 IIRC). Alas, I doubt that Soviets (people that used both P-39 and Spits in decent numbers) ever received the low-level Spit Vs.
Such Spits were far climbers than the P-39s; 3300 ft/min for the standard* P-39N/Q (7570 lbs or 7700 lbs?) on WER at SL, while Spit V (at 6450 lbs) making 4270 ft/min at 3850 ft with low-level engine, +18 lbs/ sq in. The P-39Q without the wing guns (on 7600 lbs?) was making 3700 ft/min there; with further deletion of some armor radio, maybe up to 4000 ft/min?
'Low-level' Spit V climbs 3800 ft/min at 10000 ft, P-39 (no w. guns) 3330 ft/min.

Data is obtained from Mike Williams' site, the data for * is from US 100 thousands

P39 performance per included test dated October 1941

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