The P-36

Discussion in 'Aviation' started by V-1710, Apr 15, 2009.

  1. V-1710

    V-1710 Member

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    Since the P-36 was mentioned on another thread, I thought I would start a new thread exclusively on it. Donovan Berlin's P-36 Hawk of 1934 was certainly a modern design for the day, and though it lost out to the Seversky P-35 in U.S.A.A.C. competition, the Air Corps was sufficiently interested in the Hawk to procure 3 improved prototypes. Curtiss was able to substantially improve the Hawk's performance by changing from the P&W R-1535 to the R-1830, and the success of these three Y1P-36's lead to an order for 178 P-36A's. With the P-36A, the Air Corps had a fighter that was at least as good as any fighter in the Spanish Civil War. Curtiss went on to develop many variants of the P-36, including the turbocharged V-1710 powered XP/YP-37, the aerodynamically improved XP-42, and of course the P-40. I believe the use of the V-1710 in the P-36 airframe was almost an eventuality. The P-36 was the most up-to-date fighter in Air Corps service at the time, and with the contemporary opinion that liquid cooled in-line engines were most appropriate for fighters, it should have been no surprise that the new V-1710 would be tested in the P-36 airframe. In any event, the P-36 proved to be a capable fighter in the somewhat rare instances that it was used.
     
  2. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Well, in the hands of French pilots it was surely a competent plane, with some of them racking up to 20 kills against the best air force of the time.
    Source: book "Forgotten aces" (thanks, Kris).
     
  3. davebender

    davebender Well-Known Member

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    I disagree. Switching from an air cooled radial engine to a liquid cooled V12 requires so many airframe changes that you have effectively designed a new aircraft. Installing a larger air cooled radial engine like the Wright R-2600 is less radical then switching to the V-1710 engine.
     
  4. kool kitty89

    kool kitty89 Well-Known Member

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    The P-36 was already a farily narrow airframe, such that even with the (relatively) skinny Twin Wasp the nose was a bit bulged compared to the rest of the plane, the ones with wright cyclones it was almost comical.

    This made the switch to the V-1710 fairly natural (an indeed wiht the early models there was very little difference, though the D/E changed this a bit). Much like the Fw 190 switching to an inline with the Dora. (though with the P-40 it was even simpler as I don't think the tail was lengthened)


    However there were other options (possibly better) for the P-36 airframe, using a 2-stage R-1830 (like the F4F-3) should have improved performance (esp at altitude) quite a bit, particularly if a tight cowling with cooling fan were used. (and would still retain the more damage resistant radial engine)
     
  5. V-1710

    V-1710 Member

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    Didn't say it was easy. I was only looking at it from the point of view the P-36 was regarded as the most modern AAC fighter airframe at the time and the Allison was regarded as the most modern liquid cooled in-line engine available in the US at the time.
     
  6. davebender

    davebender Well-Known Member

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    Pratt Whitney R-2000 - Wikipedia, the free encyclopedia
    Why didn't the U.S. produce the bored out P&W R-2000 as a follow-on to the P&W R-1830? The newer engine produced 1,350 to 1,450 hp (depending on fuel quality). That's excellent performance from such a light weight and compact engine. With 1,450 hp and a streamlined engine cowl the P-36 could remain competative for quite a while.
     
  7. MikeGazdik

    MikeGazdik Member

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    The Powers to be, the U.S. Air Corps, wanted the Allison. Follow the money. You want more money, put this engine in your airplane. It is that simple.

    I recall reading that the USAAC, only after pleading by some very influential higher ups, finally allowed Pratt &Whitney to continue development on thier air cooled engines instead of liquid cooled V engines that that USAAC was wanting for everything. And I believe this was during the development of the R-2800 for the Corsair.

    How about an R-2800..P-40!!!
     
  8. V-1710

    V-1710 Member

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    An R-2800 powered P-40 of sorts was built in the XP-60C. And good point about the R-2000. About the only aircraft that used the R-2000 was the C-54/DC-4, and it perfromed well in that aircraft.
     
  9. davebender

    davebender Well-Known Member

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    One of the worst production decisions made by any air force during WWII. We could have had a combination of R-2000 air cooled radials and U.S. built RR Merlins.
     
  10. kool kitty89

    kool kitty89 Well-Known Member

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    The R-2000 was designed specifically as an alternative to the normal R-1830 Twin Wasp which ran at a lower compression ratio allowing lower quality fuels to be used. It was mainly used in the DC-4/C-54.

    It did eventually develop into a pretty powerful engine, and even the early versions were capable of fairly impressive perfoemance with high grade fuel. (not a huge leap over the R-1830 though) But these lacked good altitude performance as they used single-stage (usu single speed) superchargers tuned for medium altitude. (and the critical altitude for high power at higher boost pressures allowed by high octane fuel was lower still)

    There didn't seem to be a push for this engine to be used in combat aircraft at the time (though it certainly had potential), so there don't seem to have been developments of high power versions or the use of 2-stage superchargers untile late in development. (mostly post war, I think the engines planned for the XF5U were such, though those may have been single stage too, albeit rated for 1,600 HP)


    The R-2000's development also came a bit later, so it probably wouldn't have been available until a fair bit after the US entered the war, particularly a high power combat version. (probably some time in '43)

    The R-1830 with 2-stage supercharger, such as several F4F models used would have been a good choice though, and was available prior to the US entry. (and was rated for more power than Allisons of the same time, and significantly more above ~13,000 ft)
     
  11. davebender

    davebender Well-Known Member

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    Because the U.S. Army Air Corps chose to do so. Nothing prevented the R-1830 from evolving into the more powerful R-2000 during the late 1930s.
     
  12. Elvis

    Elvis Member

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    Dave,

    On your last statement, I think the USAAC did not choose to make such a radical change to the R-1830, into the R-2000, because at the time it was fairly satisfied with its performance.
    Hindsight can be a nice thing to have and these days, we know what was coming around the corner in 1937, but at the time, I think we felt what we had was "good enough".
    Remember, a lot of improvements that happened during the war was a direct result of feedback.
    During the time you mentioned, that feedback didn't exist.
    Still, I don't see why the R-2000 never made it into a fighter plane.
    Maybe the R-2800 out-stepped it so much that a major portion of development funding was pretty much regulated to that engine, specifically.
    I don't know, but even as an "alternate" powerplant, I think it had better merit than the R-1830 and the R-1820.

    That R-2000 idea was so simple, too.
    R-1340 piston and cylinder grafted to the R-1830 crank and block.

    You'd think that'd be a sort of "dream" fighter plane engine since you're getting more power in the engine's mid and upper RPM range, and for its size, it would like running at higher RPMs.

    ...odd.

    Someone else mentioned the USAAC's penchant for liquid-cooled engines and I've heard that statement more than a few times around here.
    If that's the case, then why were ALL of our bombers radial powered?


    I'd like to see someone calculate some basic performance figures for a P-36 with the R-1830 and R-2000.
    Same with the FM-2.



    Elvis
     
  13. V-1710

    V-1710 Member

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    The USAAC's felt the in-line liquid cooled engine had the potential for greater performance in fighters, due to a slimmer profile (less drag) and the belief that engine temperatures could be more accurately maintained, allowing for greater boost with less chance of detonation. Sounds good in theory, and it certainly seemed to be the trend in Europe. The air cooled radial was deemed simpler and less expensive, so it still made sense in the USAAC's eyes as a bomber engine. The V-1710 was tried in the B-17 (as the B-38) and was proposed for the DC-4/C-54.
     
  14. davebender

    davebender Well-Known Member

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    Nothing wrong with this thinking. The problem is that the U.S. Army Air Corps failed to follow up by producing a superior liquid cooled engine. Instead they continued to produce cutting edge air cooled radial engines like the Wright R-2600.
     
  15. Elvis

    Elvis Member

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    Dave,

    I think that goes back to what I wrote earlier about things being "good enough".
    Anyway, the Brits were apparently more than happy to allow us to use the Merlin during the war.
    However, and I believe V-1710 just alterted me to this little factoid in a different thread, once the war was over, we would've had to pay R-R a fairly stiff royalty, if we wanted to continue building their engine.

    ...and just like that, the Allison is suddenly a 1500-1600 HP engine.



    Elvis
     
  16. gjs238

    gjs238 Well-Known Member

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    This a repost of an entry I made in the thread, "Could you have designed a better Warbird?"
    ==========================================================

    PART I: High altitude
    A real P-39.

    Turning the clock back to United States Army Air Corps Circular Proposal X-609 issued in February 1937, the Bell entry could have been a far superior machine than the P-39 ended up to be and would have better equipped the Allies in the critical early years of WWII.

    With existing technology, the plane could have started the war with a better wing, greater fuel capacity (providing endurance equal to or greater than the P-40), the General Electric turbocharger, gun exhaust flash suppressors, improved compass, and proper sealing/venting of nose armament fumes. Armament would be the 20m Hispano-Suiza cannon instead of the 37 mm Oldsmobile T9 and two Browning M2 .50" machine guns in the nose. Two M2's in underwing gondolas could be optional, added/removed in the field as desired.

    While the mid-engine arrangement permits heavy nose armament and a smooth streamlined nose profile, it also allows a simple turbocharger installation not requiring extensive ductwork like the P-47.

    The USAAC decision to emasculate this interceptor was a serious error. Some sources say this was done due to a change in philosophy to ground attack/close support. For that, an unsupercharged, air cooled engine powered plane would have excelled - please read below.

    PART II: Low altitude ground attack/close support
    Two competing entries:

    From Seversky/Republic:
    A P-35 developed to accept a Pratt Whitney R-2800.
    In other words, a P-43 Lancer with R-2800 sans turbocharger.
    Or a slimmed-down P-47 with R-2800 sans turbocharger if the R-2800 was not available in time for the above.
    (Please note that I'm not suggesting a modification of the P-43 or P-47, but a different evolution of the P-35 that would have led to a different P-43 or P-47.)

    From Curtiss:
    A P-36 Hawk developed to accept a Pratt Whitney R-2800.
    In other words, a P-40 with R-2800.
    (Please note that I'm not suggesting a modification of the P-40, but a different evolution of the P-36 that would have led to a different P-40.)

    These planes would be well armed with a generous fuel supply for long range loiter time.

    The development of these planes would have provided a more cost-effective, lighter, perhaps greater performance aircraft than the F4U Corsair (which I think was the only other plane being developed at so early a date around the R-2800) but whose development dragged on for some time.
     
  17. kool kitty89

    kool kitty89 Well-Known Member

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    A couple more notes on the engines. There was a similar development to the R-2000 earlier on, the R-2180 "Twin Hornet" basicly the 14-cylinder predicessor to the R-2800, however it proved troublesome, largely in power output falling short of expectations. (iirc ~1,300 hp rather than ovver 1,400 hp) It was abandoned in favor of developing the R-2800. (there was also a later, successful R-2180, but based on the R-4360 rather than the original design)

    Again the R-2000 hadn't originally been planned as a "beefed up" 1830, rather a low compression version capable of similar power (slightly more) with lower octane fuel. As things turned out they ended up using it with higher octane fuel at higher boost preassures, with later versions tuned for this. (up to ~1,600 hp WEP iirc)

    I wouldn't call the R-2600 that advanced, AFIK it never really developed into anything other than an average, slightly lower power, mediaum altitude (though this was largely a supercharger limitation) alternative to the R-2800. Of course, it's an older design, but it's also a bit wider than the 2800, though la bit lighter too. (and about the same diameter as the R-1820 Cyclone, which was, of course, much wider than the 1830)
    A decent engine design, maybe even good for some fighter disigns early war, but not particularly impressive, OK as a bedium altitude bomber/attack plane engine, or for transports. (and perfromance was fairly comperable to the single-stage supercharged medium/low alt R-2800's)



    As to the P-39's limitations and the Allison, I agree somewhat, but a big problem with the V-1710 was lack of a good mechanical supercharger available. Sure the USAAC wanted to focus on turbos, but Wright and P&W were smart enough to put development into superchargers. (P&W in particular, wich had the first 2-stage unit in service I beleive, with the Wildcat's R-1830)
    I think mechanical supercharger were generally better suited for fighters, even in cases like the P-38 and P-47 (which had particularly few issues) they would have had a good many benefits frm having high performance 2-stage superchargers instead. (reduction in weight for one, the P-47 would loose all that ducting, and "gut" reducing drag and range should be improved significantly) Especially if they'd focused on supercharger high out-put versions sooner, even if they'd started at a similar point as the early Corsair;'s 2-stage 2800, boost limitations, water-injection, and supercharger improvements would likely have come sooner if that version had been focused on.

    I t would have hurt performance above ~25,000 ft (especially with the F4U-1's engine), but reduced weight and drag would have other improvements, low alt performance improves, and most combat took place below this height anyway. (though engagement may have started around there) There should be no problems cruising higher for providing top cover either.

    Again on the P-39 though the USAAC also made the CoG problems worse (leading to the lower stability and stall characteristics) by lengthening the fuselage. Cutting the wingspan increased wingloading and reduced cruise efficiency to some extent (lower aspect ratio= higher induced drag), and the lower canopy reduced visibility and made it hard for taller pilots (above 5'6" iirc) to fit in the plane comfortably. The only positive change the AAC made was the increased fin area (vertical stabilizer), solving the lateral instability. (though this would have been a natural modification anyway)
    Moving the radiator intakes to the wing roots probably didn't hurt ither. (though it may have elimiated possible added fuel storage in that location)
     
  18. davebender

    davebender Well-Known Member

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  19. kool kitty89

    kool kitty89 Well-Known Member

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    I beleive the R-2000 was a little larger than the 1830, my refrence shows 49.1" and that data on the 2180 is the "E" model (the "Twin Wasp E" not "Twin Hornet") which was the version based on the later R-4360. (basicly a 2-row version)

    However the figures you compare are a bit off I think for comparison, you use the continuous figures for the 2180 E and military (or take-off?) for the 2000.
    It doesn't really matter though since that is the wrong "2180" to compare. (a different engine in most respects and much later)

    The original 2180 "Twin Hornet" line weighed significantly less (depending on accesories) though still a bit more than the 2000 (of comperable configuration) and was 51.6" in diameter. Power output was only a tad more than the early 2000 models, though the 2180 is an older design, and I think development had been discontinued before the R-2000 was even ready. (abandoned in favor of the follow-on 2800)
    As mentioned, development seems to have been fairly troubled and the planned output was never reached.


    See data here: http://www.enginehistory.org/ModDesig/SecI.pdf
     
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