windhund116
Senior Airman
- 360
- Jul 3, 2017
Isn't all of this more of a mental exercise than a reflection of history?
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66 Pages of still trying to turn a sow's ear into a silk purse.
Lots of coulda' shoulda' woulda' mumbo jumbo about trying to turn a mediocre low altitude fighter into a world beater.
So, just exactly how much longer was the D model than the C model?Hey guys, I'm back from my vacation from this thread, and notice it's grown a few pages. Just curious; when you all were discussing the weight differences between the P39C and D, did anybody bring up the added structural weight and moment of the elongated aft fuselage and enlarged tailfeathers of the D? The added moment would certainly require added weight forward (gearbox armor?) to keep the CG out of lomcevak land.
Actually 66 pages of me telling you that the 1942 P-39s (D/F/K/L) were way too heavy (836lbs) and could have climbed much better (1000fpm) if redundant/unneeded items were deleted, and showing you the official performance tests.66 Pages of still trying to turn a sow's ear into a silk purse.
Lots of coulda' shoulda' woulda' mumbo jumbo about trying to turn a mediocre low altitude fighter into a world beater.
only the Soviet Union loved it, and they did great with it.
So, the total losses of the Messerschmitts amounted to exactly 103 ******* aircraft, including 42 destroyed and 61 damaged. Of these, only 27 "Messers" were destroyed in air battles and 23 more received various damage. In other words, Soviet fighter pilots, who during the battles in the Kuban were credited with more than 700 (!!!) "shot down" Me-109s (calculations are made on the basis of data from the book by M. Yu. Bykov), in reality, can celebrate victory over them only, exactly, in fifty cases. And, if the Germans exaggerated their successes, on average, 2.5 times, then ours increased this indicator, on average, up to 14 times, although there were exaggerations and much more.
Could go in the "What If" section
Hello Juha3,
My credentials are fewer than yours.....
What document did that page come from? There are a few odd aspects of the M-82FN that I am interested in and perhaps I have the document you are referencing. I don't like to read through a bunch of Russian manuals unless I know I will find something.
From what we KNOW:
The critical altitude of the M-82FN was 4650 Meters.
From what various sources state:
The maximum speed has been given as low as 625 KPH and as high as 648 KPH.
The critical altitude for the La 5FN has been given to be as low as 5000 Meters and as high as 6250 Meters.
How do we reconcile all these?
Here is what I BELIEVE. (Emphasis on Believe but it seems to fit all the data points.)
With an engine making its best power at 4650 Meters, I believe a very good example of the La 5FN could reach 648 KPH at 5000 meters. This would be more typical of expectations for ram effect.
By 6000 Meters, its speed may have dropped to 635 KPH which is also pretty reasonable.
If you believe that speeds were 10 KPH slower at each altitude, I won't argue. Production quality did vary quite a bit.
- Ivan.
Hello Ivan
The docu, unfortunately I cannot recall where I got it, my memory is not as good as it was say 30 years ago and as a pensioner my procedures have became more sloppy.
On La-5FNs, I must disagree, Russian authors clearly state that those speeds are max. speeds, and because the altitudes varied the question is not speeds at certain altitude. Some tables show max speed for both stages and also max speed at 5,000 m, for some reason Soviet authorities thought that 5,000 m is an important altitude, usually the climb times shown in Soviet WWII docus are to 5,000 m. And in the attached table you see that the speeds at 5,000 m is lower than the max speeds for 2nd stage. There is also the La-5FN proto with its 648 km/h max. speed, it achieved 622 km/h at 5,000 m.
View attachment 600837
This is simply not true. By 1943 the single stage Griffon Spitfire was in service, the Alisson engine P-51 was superior to the P-39. There is the Typhoon the P-47 how does it compare to the Hellcat and Corsair? A clipped and cropped late model Spitfire MkV was a good performer at low level on higher octane and boost, it would do a lot better if you take the cannons and armour out of it but that was specified military equipment, this discussion has been part of the P-39 history since the moment it arrived on UK shores, it is why they only did one mission from UK and all were then sent to Russia.Actually the P-39N was very competitive with anything in 1943, except possibly the Spitfire IX and the Merlin P-51 in the last month.
The early P-39s (D/F/K/L) would have been competitive with anything in 1942 had they not been 800+lbs overweight, as the AAF finally figured out. Except the two stage Spitfires.
If the P-39 had received the two stage V-1710-93 in early 1943, it would have been competitive with pretty much everything. Not nearly as heavy as the P-63 and much earlier.
ACTUALLY...Actually 66 pages of me telling you that the 1942 P-39s (D/F/K/L) were way too heavy (836lbs) and could have climbed much better (1000fpm) if redundant/unneeded items were deleted, and showing you the official performance tests.
And you all telling me that the 1000fpm difference in climb between the two planes was from a slightly different propeller of the same diameter, an inch or two more length, a fin fillet, phantom CG issues that weren't there in the test planes, and other irrelevant mumbo jumbo.
And a few pages of your personal firearms.
Actually the P-39N was very competitive with anything in 1943, except possibly the Spitfire IX and the Merlin P-51 in the last month.
Tail feathers were pretty much the same but the C had two .30 cal guns and ammo in the nose (a bit further forward of the .50 cal guns) so several feet in front of the CG .but these were shifted to the wings and one more added on each side, Weight went up but the wing guns and ammo are pretty much on the CG, probably didn't do much for roll response though.Just curious; when you all were discussing the weight differences between the P39C and D
Hello Juha3,
There is only one stage in the supercharger, so we are really talking about first speed or second SPEED.
First speed hit its critical altitude at 1650 Meters.
Blower shift to Second speed happens at 4000 Meters.
Second speed hits its critical altitude at 4650 Meters.
Now, this is for "Military Power" or 1000 mm Hg @ 2400 RPM.
Although the supercharger cannot provide any additional boost past 4650 Meters, do you happen to know if some of these tests ran up to 2500 RPM (Take-Off RPM) at altitude?
Is it possible the superchargers were different in the prototypes?
It just seems quite unusual for an aeroplane to make its best speed at 5700 Meters to 6250 Meters when its maximum engine power was achieved at 4650 Meters.
Anyone more knowledgeable care to comment?
- Ivan.
Weight was actually only reduced by 600+lbs which allowed the P-39K to fight at 27000'. Best Japanese bombers G4M came in at 18000'-22000'.Gen. Harmon was unhappy with the performance of the P-400 over Guadalcanal; 67th Sqd had been roughly handled in it's first engagement, and in consequent engagements, the inability to get up to the altitude of the incoming bombers. The main reason being that the P-400, originally intended for the British, were equipped with a high pressure oxygen system; 'no supply of high pressure oxygen bottles were available om Guadalcanal' so they were forced to operate at low altitude (p. 85 of the report). There were other issues as well, even if the oxygen supply problem was solved, Harmon (and Vandegrift) did not consider the plane suitable as an interceptor and out-classed by the Zero.
In the attachment I have highlighted the suggestion given Harmon that the P-39's enroute to New Caledonia could be stripped of some 1500 pounds (20% of it's operational weight, in the field ?!?) and pointed to Australia where ...'considerable success with P-39's against Zeros is being achieved'.
By Australia I guess was meant New Guinea, which I believe was the only scene of combat between P-39's and Zero's at this time. The P-39 units there were credited with 95 victories against Zero's (15 actual losses), so the percieved success was not all that 'considerable'.
Please go to wwiiaircraftperformance.org and look at the P-39N climb numbers. Then look at the P-51A, Typhoon, P-47(1943), Hellcat, Corsair, Spitfire V, FW190 and Zero climb numbers. P-39N substantially outclimbed all those planes in 1943.This is simply not true. By 1943 the single stage Griffon Spitfire was in service, the Alisson engine P-51 was superior to the P-39. There is the Typhoon the P-47 how does it compare to the Hellcat and Corsair? A clipped and cropped late model Spitfire MkV was a good performer at low level on higher octane and boost, it would do a lot better if you take the cannons and armour out of it but that was specified military equipment, this discussion has been part of the P-39 history since the moment it arrived on UK shores, it is why they only did one mission from UK and all were then sent to Russia.