Was the P-40N much faster than P-40E?

Discussion in 'Aviation' started by skiswimcycle, May 20, 2008.

  1. skiswimcycle

    skiswimcycle New Member

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    I have read a few of Osprey's P-40 Aces books, and was wondering if the P-40N series was really much faster than the P-40E series. Some websites claim P-40N's could break the 370mph barrier? Was that a prototype without any guns or armour to slow it down a bit?
     
  2. seesul

    seesul Active Member

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  3. Jerry W. Loper

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    I'm at work and away from my books (I have a 2-volume paperback set about the P-40 written by Bert Kinzey, which I think has pretty authoritative specs). But IIRC, early production blocks of the P-40N had a speed of 378 m.p.h., but these were lightweight aircraft with only four .50-caliber guns. Later blocks of the P-40N model were heavier (including restoring six-gun armament) and had a speed of only 343 m.p.h. I think the P-40E had a speed of a little over 360 m.p.h. P.S. The early P-40Ns were not the only P-40s with speeds of 370 m.p.h. or better; the XP-40Q had a speed of 422 m.p.h. and a couple of models (I think the L and M models) had speeds of 370 m.p.h.
     
  4. Thorlifter

    Thorlifter Well-Known Member

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    Jerry,

    What did the Q model have in it that made it so fast?
     
  5. Jerry W. Loper

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    IIRC, its engine was a 1425 h.p. Allison V-1701-121 and its airframe had been so re-designed that it scarcely resembled a P-40 any more. (Its armament was reduced to four guns, plus the wings were clipped, the fuselage was cut down, the distinctive radiator "mouth" that was the trademark of P-40s was done away with, and a bubble canopy replaced the familiar box canopies of all earlier P-40s.) Also IIRC the XP-40Q's ceiling was also dramatically better than older P-40s; about 39,000 ft.
     
  6. Thorlifter

    Thorlifter Well-Known Member

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    1. What does IIRC mean?

    Here is a pic
     

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  7. Jerry W. Loper

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    IIRC = if I recall correctly
     
  8. kool kitty89

    kool kitty89 Well-Known Member

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    It wasn't the increased power of the P-40Q's engine, but the greatly improved altitude performance. (2-stage supercharger)

    If you look at the actual power ratings (WEP) the P-40E had 1440 hp available at low altitude. However power dropped rapidly above 5,000 ft. Mil power is often listed for the performance figures which was usually 1,125 hp. The P-40M/N's V-1710-81/99 engine had significantly better altitude performance due to a higher supercharger gearing ratio (at the expence of max bost at low alt due to risk of detonation) and had a crit alt of 10,500 ft for 1,480 hp for high speed level flight, and 1,125 hp at 17,500 ft. (added ram effect at high speed) (for safety takoff was limited to 1,200 hh, originally 1,360 hp)
    Those gave the P-40N a top speed of 378 mph at 10,500 ft, and 362 mph at ~19,000 ft. With the same engine the P-51A did 415 mph at 10,500 ft, and 408 mph at ~18,000 ft.

    And the P-40E's V-1710-39 or F3R engine had a max boost of 60" hg at low altitude giving power levels of 1,570 hp, giving the P-40E a performance atvantage below 8,000 ft. (the P-40K with -73/F4R engine moreso) Overboosting produced power levels in excess of 1,700 hp.

    Perils P40 Archive Data

    http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/Allison 1710-39 abuse.pdf
     
  9. HoHun

    HoHun Active Member

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    Hi Jerry,

    >But IIRC, early production blocks of the P-40N had a speed of 378 m.p.h., but these were lightweight aircraft with only four .50-caliber guns.

    Hm, with regard to actual test data, I didn't find anything faster 355 mph @ 15000 ft as achieved by a P-40N-1 at 57" Hg, 3000 rpm in RAAF tests for any Allison-powered model.

    However, Claidemore has posted a general speed comparison chart showing the 378 mph figure you quoted, showing that regardless of its accuracy it's a figure from authentic historical documents at least:

    http://www.ww2aircraft.net/forum/aviation/saburo-sakai-zero-vs-bf-109-a-1042-5.html

    At optimum altitude, the P-40N-1 tested by the RAAF would have made 360 mph or slightly more, but not 378 mph. (It's possible to calculate that fairly accurately.)

    My friend Peril has collected a lot of useful P-40 data on his site:

    Perils P40 Archive Data

    I have to say I haven't looked at all of the stuff presented there since he put up quite a bit more since we did our analysis a couple of years back, so there is a certain chance you could find faster test data and prove me wrong - I'd be glad to adjust my analysis then :)

    Regards,

    Henning (HoHun)
     
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