XP-82 Restoration Update

Discussion in 'Aviation' started by GrauGeist, Nov 16, 2013.

  1. GrauGeist

    GrauGeist Well-Known Member

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    Been keeping an eye on the restoration of the XP-82 (44-83887) and here's some recent info at the Warbird News Site: North American Twin Mustang Prototype XP-82 Being Restored to Flying Condition

    For those of you who weren't aware, one of the oldest surviving F-82 airframes out of 5 existing world-wide, is undergoing extensive restoration. So old in fact, that it's the second prototype airframe and officially carries the designation of XP instead of P or the later F designation.

    Although the early XP-82 aircraft were built and flown during the last months of WWII, their production counterparts were put into operational service after the war was over.
     
  2. drgondog

    drgondog Well-Known Member

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    These are the beauties from the first 20 that had Packard Merlins - and Always performed better than the blanket blank Allison 1710-143's. Edgar Schmeud's greatest lament was that the Sec Def forced General motors/Allison on NAA
     
  3. GregP

    GregP Well-Known Member

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    #3 GregP, Nov 19, 2013
    Last edited: Nov 19, 2013
    It seems Schmeud didn't like the Allisons, but the Allison P-82's had one -143 and one -145, not a pair of -143's. One turns left and the other turns right.
     
  4. T Bolt

    T Bolt Well-Known Member

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    I didn't realize that the P/F-82 ever had Merlin engines. Were they right and left turning engines like the Allisons?
     
  5. GregP

    GregP Well-Known Member

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    #5 GregP, Nov 20, 2013
    Last edited: Nov 20, 2013
    Yes. They originally turned inward and the plane wouldn't take off! They reversed the engines and things went well. Nothing wrong with the Merlins. Despite the protests to the contrary above, we don't have many problems with Allisons either, even 100-series engines, which most today are.

    Both have occasional issues; many are self-inflicted. For instance, we had one Allison customer who disassembled his oil pump and nicked the seal when he tried to reassemble it. He had to send his oil pump in to the shop for work and correct shims since he dodn't note the shims as he disassembled it. When we asked why he disassembled it, he said he was curious about it! No training and no spares, but he felt qualified to disassemble an Allison oil pump without a manual or a parts diagram. I cannot credit that as an engine issue, even though his engine was down for a short while. We;ve had several who continued running the starter way past the safe limit and essentially melted the starter. Even cars have a "safe cranking time." If it doesn't start by then, stop, reassess, and try again. We even had one guy who drained his oil and proceeded to start the engine when a friend came over and let it idle long enough to require new main bearings!

    Merlins also have occasional self-inflicted issues, so this in NOT uncommon, but also not frequent. Most people don't meddle where they shouldn't without the knowledge to meddle there, so it isn't a big issue ... and people who do it are embarassed, to say the least.

    At the Planes of Fame, our Merlins run reliably, as do our Allisons. You don't often see our P-51's, our P-38, P-40, P-51A down for engine issues. The P-51A is usually down for radiator issues whnen it is down, not the Allison. We're making a new radiator of our own design ... hope that cures it! In fact, most of out WWII planes are very reliable.

    In general, the Merlins and Allisons need different maintenance. For instance, every 25 hours you have to re-torque the cylinders on a Merlin. You NEVER have to re-torque an Allison cylinder assuming it was done correctly in the first place ... until you disassemble it and untorque the cylinder hold down nut. You would only do that when you change cylinder liners. But that is not a knock on the Merlin or a point for the Allison; it is a design choice with design maintenace requirements. Neither design is superior to the other ... they are just slightly different.

    The Allison valve seats are in the head itself and never change height unless they are ground for seating purposes. The Merlin valve seats are screwed in until they break the franglble link and are then ground for seating. Again, neither cylinder hold-down design is better; it is a design choice. I DO like the Merlin's 2-stage supercharger bertter thanh the Allison supercharger - turbocharger but, in use, after the P-38's issue were corrected, it flew relaibly and well. The P-47 ALSO flew reliably and well with a turbocharger as the high-altitude boost system, as did the B-17 and B-24.

    A few features of the Allison ARE better. The nose case is bolted on, so it can be changed from a prop shaft to a driveshaft for remote drive (like in a P-39 / P-63). The crankshaft and rods are much stronger than a Merlin's, but neither is weak at stock power levels. The Merlin's nose case is cast into the block, so it is difficult to adapt it to something like, say, a PT boat or a tank. They DID, but it was more difficult. The Allison was easy ... change the nose case for the drive you needed.

    In the end, I think the Merlin proved a better engine in WWII field use in the ETO, but the Allison is a very good choice today for a warbird, assuming you can find an Allison-powered warbird, have the money, and are in the market. On the other hand, there is nothing wrong with a good Merlin warbird and I'd take a Spirtfire or P-51 if I had the means. Actually, I'd prefer the Spitfire despite being a US citizen. To me, the Spirfire, Bearcat, and Zero are the most asthetically-pleasing warbirds on the planet, but that is a matter of taste, and nobody needs to agree or disagree for it to be true. Your choices may differ, and that's just dandy.

    I can't see affording a Zero since the population is so small. As it happens, we have the only one in the world running the original Nakajima Sakae 21 engine and Mitsubishi prop at the Planes of Fame, so the population is one plus a few other running American engines and propellers.

    Gimme a Spit! Don't care what mark it is ... and don't care if the Merlin is British or US, either one would be just fine. I WOULD want a Rotol prop, though and a real Spitfire stick assembly that breaks in the middle, with the round grip. I'd put the radio push-to-talk on the gun trigger (MG, not cannon). I can dream, and it's only a lottery win away!
     
  6. GrauGeist

    GrauGeist Well-Known Member

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    I would love to see one in flight, I have always thought they were incredible machines.

    Heck, it was simply awesome to see a P-51H fly into Redding and to stand there looking at one up close was something that may never happen again in my lifetime.

    I think it's a tragedy that so many warbirds have been lost to time, but on the otherhand, these are exciting times as more warbirds than ever are being recoverd and resurrected.
     
  7. vikingBerserker

    vikingBerserker Well-Known Member

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    That's really cool! Why the heck would it not take off with the engines turning inward?
     
  8. drgondog

    drgondog Well-Known Member

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    He didn't like the performance delivered by the 1710-143/145. They sucked and never reliably delivered on the WI WEP despite Schmeud fixing one at NAA and telling Allison how to fix their engines. The Allisons were forced on NAA because the DefSec killed Rolls royalties and ordered Allison.

    The P-82 was handicapped from its early XP-82 series w/1650-9/11 when the Allisons were installed.
     
  9. GrauGeist

    GrauGeist Well-Known Member

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    The inner wing provides about 25% lift and the prop wash was negating the lift from that portion of the wing.

    Problem was solved after they swapped the engines.
     
  10. Aozora

    Aozora Well-Known Member

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    The official project website is http://www.xp-82twinmustangproject.com/ Some really interesting details can be found in the monthly updates under (eg) "2013 Newsletters Photos" - looks like the project is in very good hands, including the cats (see October 2013.)
     
  11. GregP

    GregP Well-Known Member

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    Well Bill,

    Let's say we disagree about the "handicapped" part. And by the time the P-82 was in service, the difference of about 10 - 12 mph was meaningless as jets were the new darlings of the USAAF / USAF, and the P-82's were never going to be first-line fighters. From talks I've heard by the people who were there, the Allisons had some troubles simply because the jets were the darlings and the pistons weren't getting reliable maintenance and depot service. In that situation, the Merlins might just as easily have done about the same. I wasn't there and can't say for sure, but I CAN say we haven't had much in the way of troubles with the 100-series Allisons we built at Joe Yancey's shop.

    They are running just fine, although obviously not at 25 - 35,000 feet and not frequently at high power settings other than for takeoff and climbout. So, it is possible the Allison haters had some justification. It is also possible they just wanted Merlins and glossed over the issues they had with Merlins. Again, I can't say.

    At the Planes of Fame, our Merlins and Allisons are both reliable, as I have stated before. The end of the war DID mean the end of piston development EXCEPT for the V-1710-143 and -145, and Allison knew vey well that these dash numbers would be the end of the line.

    Although I have nothing against the merlin, I also have not experienced the supposed unreliability of the Allison. They fly fine, so I conclude they FLEW fine. They won a lot of Hydroplane races and are on top of the tractor pulls today. The evidence just isn't surfacing and we fly both makes on a regular basis.

    So my own observations are not proving the Allison-bashers to be correct. I've seen Merlins have issues, too, but I don't assume they have design problems because the engines develop occasional trouble. And the speed difference may well have been due to different propellers as much to different engines. I'd like to have seen one fitted with Allisons flown with teh same props as on a Merlin-powered unit ... it WAS and IS possible. All it takes is the correct-spline prop shaft.

    If it was still slower, it might be time for an investigation .... but not really. As I said, the P-82 was never going to be a first-line fighter once jets were in service anyway. It flew just fine as it was. That is, of course, only my opinion. I can see yours differs. I suppose that means when we get OUR P-82's you;d go with Merlins and I'd go with Allisons. Don't know about you, but mine will take a long time to be purchased.
     
  12. vikingBerserker

    vikingBerserker Well-Known Member

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    Ok, that makes a lot more sense, THANKS!
     
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