P-38 vs P-82

Discussion in 'Aviation' started by gjs238, Nov 20, 2012.

  1. gjs238

    gjs238 Well-Known Member

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    Which performed better and why?
    Shouldn't the P-82 be a less effecient way to design a twin engine fighter than the P-38?
     
  2. tomo pauk

    tomo pauk Creator of Interesting Threads

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    P-82 was far a better performer. Using all the good things from P-51 (general wing profile, radiator design), along with engines that were providing both prop and exhaust thrust, and being a 2 men plane from day one - it simply got to work well.

    The only major thing the P-38 had over it was a crucial one - timing.
     
  3. zoomar

    zoomar Member

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    Do we really know how the P-82 would have fared in fighter vs fighter combat against WW2 single seaters? In Korea it was mostly a night intruder, wasn't it? No question it was faster than the P-38, but it was about a 10 year newer design than the P-38. I'm not really sure the two planes should be compared.
     
  4. Shortround6

    Shortround6 Well-Known Member

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    The compare sort of like an F-86 and an F-100.

    The F-82 was a few years ahead of the P-38 in aerodynamics and a few more years ahead in engine/fuel technology.

    F-82 was a bit bigger airplane. about 25% bigger wing and about 3,000lbs more empty weight.
     
  5. davebender

    davebender Well-Known Member

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    P-51D didn't arrive in Europe before the summer of 1944. When do you anticipate the twin Mustang entering service?
     
  6. steve51

    steve51 Member

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    The P82 received credit for destroying a number of North Korean Yak9 and IL10s in air combat.
     
  7. dobbiemiko

    dobbiemiko New Member

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    There are good P-82's and bad P-82s from what I understand. The good ones were the first made, but then the US decided not to pay RR royalties on the Merlin engine, so the design reverted to Allison V1710s. Lots of maintenence headaches with the design and because of the handed Allisons, spare parts became an issue. The aircraft didnt last through the Korean war. Jets were taking over in every field, so no more money was sunk into the prop jobs.
     
  8. drgondog

    drgondog Well-Known Member

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    Dave - strictly speaking the combat operational P-51D's were flying with 4th and 354th FG in late May 1944 but they 'arrived' in late March, uncrated and modified radios, etc for ETO ops'
     
  9. drgondog

    drgondog Well-Known Member

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    The first 20 were built with the 1650-9 and -11, thereafter with the 1710-143/145. It was a pretty damned good engine. The decision about continuing the Merlin lne was made in late 1944 and both the supercharger and carburation approach was still in flux.

    Actually the P-82 was still the Only long range escort available for SAC and the only long range night fighter available for the Alaska/Canada DEW line of defense so the rerirement started in 1952 but they soldiered on till 1954.
     
  10. drgondog

    drgondog Well-Known Member

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    IIRC the Korean War dayfighter credits were 3-1-2 for zero losses... medium altitude.
     
  11. Timppa

    Timppa Active Member

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    At least Schmued disagreed on that.
     
  12. GregP

    GregP Well-Known Member

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    Regarding post #7, spare parts were never an issue with the left and right-turning Allisons. Both used the same parts except for about 5 - 6 parts, and these particular parts don't break, they are merely gears in the accessory housing, a stater dog, and a handed starter. The handed engines use the same crankshaft, same pistons, same cams, same valves, same heads, etc. You DO need a starter that turns left and right, and they are very robust. We've never had one fail yet in all the years we have been overhauling Allisons.

    Personally, I prefer the P-82 with the V-1710 G-6 engine, but that's me. The ones we build run great!
     
  13. drgondog

    drgondog Well-Known Member

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    Timppa - could you suggest a location for his comments? I know he didn't like the idea of going the supercharger route because of the weight but haven't seen any comments regarding performance or reliability of the Allison?
     
  14. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Regarding spare parts, this is from Wiki...

    "On 30 June, FEAF requested HQ USAF for an additional 21 F-82 aircraft, which was denied. In addition, the projected level of support which could be provided at the level of combat usage FEAF was experiencing was no more than 60 days due to a shortage of parts. The fact was that, when F-82 production ended in April 1948, no provision had been made for an adequate supply of spare parts, as the aircraft was not expected to remain in operational service once jet-powered aircraft were available. Further, the Air Force simply did not have that many F-82s in the first place (182 total operational aircraft), and did not want to weaken the F-82 units committed to the Pacific Northwest or Atlantic coast, or to draw from the fourteen F-82Hs in Alaska."
     
  15. GregP

    GregP Well-Known Member

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    In fact, when the F-82 was ordered, the prototypes had Merlins in them. The first prototype flew 26 June 1945. Since the war was ending, Rolls Royce was bumping up the license fee for the Merlin and the US Army Air Corps asked Allison to design a new, higher powered V-1710 for the plane. They undertook to do this and the Allison G series resulted. However, in the Air Corps, the powers that be were MUCH more interested in jets, and cut the anticipated and dangled order for 1,000+ P-82’s to under 300 aircraft. In the end they delivered 270 aircraft and the P-82 was the last propeller-driven fighter ordered in “quantity” for the Air Corps / USAF. The Army Air Corps got EXACTLY the spares they ordered.

    Allison did not produce engines without orders from a customer and most businesses won’t either when the product costs as much as a V-12 engine costs. The powers in the Air Corps / soon-to-be-USAF were not really interested in the P-82 / F-82 and didn’t order normal or even close-to-normal spares or even bother to keep up with suggested maintenance, even going so far as to fly the G-series engines well beyond recommended overhaul. Many of the P-82’s were grounded for lack of spares that weren’t even engine related. Some parts are typically “consumable,” but engines usually aren’t. Things like seals, O-rings, filters, etc. require changing at regular intervals, much like a car.

    The Allison G-series engines we build run just fine and, when operated by the book, give good service. But the Air Corps didn’t even keep up with new pilot training. Many P-82/F-82’s were flown by people given only a brief “cockpit checkout.” I flew radio control for a LONG TIME and one of the people I flew and talked with in Phoenix, Arizona an several events was Col. Robert E. Thacker who holds several P-82 records including one from Hawaii to New York. He said that the P-82 was a bit of a “Stepchild” and was sometimes flown by people with little training in it. It was a propeller fighter in a time of transition to jets and was not exactly lavished with care. Basically, they wanted the props to “go away” and every red-blooded fighter jock wanted to be assigned to jets.

    When the spares dry up, the planes sit out in the weather (since the jets were in the hangars) and don’t exactly get better or even stay the same. They deteriorate unless they are active, like any machine.

    It is incorrect that the Allison G-series engines were the major reason for the P-82’s main headaches. They experienced issues because the service didn’t want them, didn’t order even half the normal spares, didn’t do much of the regularly-scheduled maintenance, didn’t even pursue piston pilot training past the first couple of classes, and didn’t pursue piston mechanic training either since they were being retrained on jets. As fighter piston mechaincs left the service, they were not replaced. They certainly didn’t do the normal carburetor overhauls every 2 – 3 years these days, but scheduled every year when in service.

    Our Allison V-1710 G-series engines run just great, and I firmly believe the new ones at the time did too, especially since our G-engines are the SAME ones that were produced and used at the time. Sorry, I don’t buy the old, tired Allison-bashing based on personal experience with the Allison. They run just fine for years. At least ours do.

    Not trying to start anything, but also not going to hear the some old Allison-bashing without a reply. We currently have an order backlong of 20 engines and more than 60 in service in flying aircraft. We have Allisons out there running fine after 12 - 15 years in the plane! Does that sound like an unreliable engine? Our biggest issue with our run-stand left-turn engine for the past 6 years has been keeping the battery charged, not the engine (we don't run an alternator since it is just a display engine). Otherwise, it starts and runs every time, and we use it to train new Allison owners how to start and run their newly-overhauled Allison.
     
  16. dobbiemiko

    dobbiemiko New Member

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    I believe the Allison V1710 series engines are one of those underdog powerplants which never was recognized for what it could do, and at low/medium altitudes, could do quite a lot just as it is. The AAC wasnt interested in developing advanced superchargers for its fighter aircraft, so who could blame Allison for not doing so? Contract money for military aviation was very tight in the 30s on everyone. Youll never hear me talk bad about an Allison engine-probably as close to a modular design as there ever was in a liquid cooled V-12. I knew the 82s had a bad rep and thanks to a few here, I now know why. It surely wasnt the fault of the builder....
     
  17. CobberKane

    CobberKane Banned

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    Was there anything inherent in the Allison's design that made it difficult to etract the kind of performance obtained from the Merlin - by which I mean was the Merlin a 'hotter' engine - or was it more a matter of supercharger technology?
     
  18. tomo pauk

    tomo pauk Creator of Interesting Threads

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    #18 tomo pauk, Nov 22, 2012
    Last edited: Nov 22, 2012
    When the V-1710 went into service, it was either single stage, single speed, or a turbo machine. Turbos were preferred by the US Army, but the initial issues with the turbo set-up basically forced the Army to adopt the single stage version for it's P-39s/-40s, in order to have modern planes in service in short time.
    The Allison was proposing several versions of it's V-1710 (with fuel injection, with auxiliary supercharger, etc...) to the Army, but neither the Army was interested in those, neither Allison had the resources (skilled manpower) to start developing those versions prior, say, 1942. By that time the 2 stage Merlin is almost in service. North American was proposing a two speed V-1710 for Allison to produce, some time in 1941, but that too never 'took off'.
    Once the 2 stage story gets rolling, Allison made a mistake/oversight to install the carburetor prior the auxiliary (1st) stage - that cost some 2000-2500 ft in full throttle height (it was only 22400-22500 ft because of that, for 1150 HP).
    What was the 2 stage V-1710 capable was shown in late models (built in late war, but never went in service), when the carburetor was relocated between the supercharger stages, the crankshaft received 12 counterweights (so the 3200 rpm was allowed for take off, military and WEP rating), the step-up ratio of the auxiliary supercharger increased, all while using water injection to cool the charge - the engine went to, say, 1700 HP at 26000 ft for the V-1710-121, flying in aircraft prior the ww2 ended. But that was too late to matter. Post ww2 engines for the P-82 were further modified, to allow for intercooling.

    The Merlin have had some definite advantages: it's induction system was of a greater area (that gave cca. 2000 ft for the full throttle height vs. the single stage V-1710); the 2 stage Merlin was a far more compact engine than a 2 stage V-1710; it was designed from the outset to be intercooled; the early fully supported start was surely it's greatest advantage.

    added: wartime V-1710s have had the compression ratio of 6.65:1, Merlin was 6:1. Lower compression ratio allows higher boost, prior the detonation to occur. The increased RPM of the late V-1710 has one shortcoming - the reduction gear (for the propeller) need to be changed as well, since the propeller will overspeed become inefficient. That could lead to the change of cowling, in a classic engine-in-front plane layout.
     
  19. tomo pauk

    tomo pauk Creator of Interesting Threads

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    In Vee's for victory, the author repeats Schmued's words (from the book 'Mustang engineer') that V-1710s used for P-82 were incapable to make more than 60 in Hg. GregP covered the issue (background of the G-6 engines) more or less as it's covered in Vee's.
     
  20. drgondog

    drgondog Well-Known Member

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    Timppa/Tomo - simply you are correct. The background and history are contained on pages 151 through 158 of Mustang Designer.

    The Allison 1710-119 was originally tried in the XP-51J and had a host of problems which were not solved for the -143/145. From the book, the primary issue was that Allison would not install a backfire screen to prevent case damage when engine was boosted past 60 in. NAA actually modified a couple to install the backfire screens and they worked - but Allison refused to modify their engines and SecDef Forrestal told the USAF to stand down.
     
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