P-51 problems...

Discussion in 'Flight Test Data' started by seesul, Feb 18, 2009.

  1. seesul

    seesul Active Member

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    Interesting reading...I ´ve found it while browsing on net...

    The Merlin P-51 had a lot of teething problems, but, for some reason, they
    are largely overlooked. It had problems with the canopy frosting over,
    with jamming guns, with the engine cooling system and the engine
    itself--and with shedding the tail. In fact, the plane had so many
    problems initially that Col. Don Blakeslee, CO of the 4FG, called it "an
    experimental aircraft" and expressed doubts that it could be successful.
    The P-38 had gone through its teething troubles the previous fall and with
    the introduction into ETO combat of the J model well-pleased its pilots.
    FGs getting the P-51 were unhappy and pilots grumbled that they would
    rather have the Lockheed. It was not uncommon to have almost 30 percent of
    P-51 sorties aborted for mechanical reasons during the winter and spring of
    1944 (typical abort rate for all causes for all USAAF aircraft was 8 percent).
    When the D model became available in quantity in the summer, cases of the
    aircraft losing its tail surfaces in flight began to be reported. Flight
    restrictions were placed on the aircraft and the tail surfaces were beefed
    up. Wing failures were also reported due to control stick force reversal
    in high-speed dives. The bobweight was added to the elevator control
    system to fix this problem. But for the aircraft to be even marginally
    stable, the fuselage fuel tank had to be less than half full.
    The Mustang still had problems a year later when the 7AF began B-29 escort
    missions to Japan. Incidences were reported of tail surface failures in
    dogfights. In one instance in April, 1945, a P-51D got into a dogfight with
    a Mitsubishi Raiden. During the violent maneuvering, the Mustang first
    shed its tail control surfaces and then its wings were torn off. The
    pilot, 2Lt. James Beattie, did not get out. The Raiden apparently suffered
    no damage from the severe loads placed on it during the dogfight.

    All that said, the Merlin Mustang was a very effective fighter, but its
    greatest successes came in the ETO, where its high abort rate would not
    result in equally high pilot fatalities. Over the vast reaches of the
    Pacific, the P-38 was the fighter of choice. Mustangs suffered their
    greatest operational loss of the war on an escort mission to Japan when 27
    out of a force of 148 went down. Most of the losse were weather-related
    (always a greater danger than the enemy in those days) rather than
    mechanical failures, but the Mustang seemed dogged by bad luck and had
    little success battling Japanese fighters over the home islands. The
    contrast with its sweeping victories over the Luftwaffe is striking.
    P-38 pilots relate the story of an apparently new-in-theater pilot who
    called over the radio, "Mayday! I've been hit and am losing coolant. What
    should I do." To which a P-38 pilot replied, "Calm down. Just feather the
    prop and trim for single-engine flight and you'll get home okay." There is
    a long pause, and then the first pilot says, "Feather it, hell! I'm in a P-51."
    Mustang pilots in the PTO sang a ditty that went:

    "Don't give me a P-51.
    It was all right for fighting the Hun,
    But if fighting the Jap you try,
    You'll run out of sky.
    Don't give me a P-51."

    (The reference to "running out of sky" refers to the great amount of
    altitude lost in dogfighting the maneverable Japanese fighters.)

    In contrast, they sang about the Lightning:

    "The P-38 is some machine,
    The answer to a flyer's dream.
    She'll dive, loop and climb
    And turn on a dime.
    To every pilot, she's the queen."

    It's interesting that these two ditties imply that pilots thought the
    P-38 was more maneuverable than the P-51. It could be that they simply
    trusted the Lockheed not to come apart during violent maneuvers, and were
    leery of pushing the North American fighter. It's even more interesting
    that in the MTO and the ETO, apparently, P-38 pilots were a little afraid
    of their mounts and hesitated to dogfight Luftwaffe fighters. Go figure.

    and

    The P-40 was the starting point for the P-51 design: North American set
    out to design a fighter with superior performance than the P-40 that would
    use the same engine (Allison V-1710) and be more or less the same size.
    The prompt was a British Purchasing Commission request for North American
    to build P-40s under license, as it wanted to order more of them than
    Curtiss could build. Britishers often say that the Mustang was built to
    British specifications. That's oversimplifying. The design was essentially
    North American's, but the BPC did specify that NA buy the wind tunnel and
    flight test reports of the Curtiss XP-46 fighter to be used to help develop
    the NA fighter. NA engineers claim that although the company acquired this
    material, it was not used in the development of the P-51.
    The P-51 design used a boundary layer gutter that separated the cooling
    air intake from the fuselage, preventing the intake from ingesting the
    boundary layer (the layer of turbulent air close to the skin of the plane.
    It was a brilliant idea, and folks are still squabbling over who suggested
    the idea. Some say it was Irving Ashkenas, an NAA aerodynamics engineer.
    (He is also credited with moving the radiator air duct from the nose to the
    belly of the plane.) Others say D.B. Shenstone, a Rolls-Royce engineer,
    suggested it.
    The P-51 also used a laminar flow wing, which greatly reduced drag. The
    wing design was based on work done by NACA (predecessor of NASA). The
    square wingtips were based on pre-war work done by German researchers (Bf
    109 had square wingtips). The laminar wing greatly reduced drag, but it
    gave no warning of an impending stall, making the airplane a tricky one to fly.
    It was British input that replaced the Allison engine with a Merlin. The
    Allison was a smoother engine than the Merlin, but it only had a
    single-stage, single-speed mechanical supercharger, thus limiting engine
    performance at altitude. The Merlin version put in the P-51 had a
    two-stage, two-speed mechanical supercharger, which allowed the engine to
    perform well to high altitudes.
    The shift from first to second speed in the first stage of the
    supercharger was barely noticeably, a mild kick at about 8,000 ft., sort of
    like downshifting your car from 4th to 3rd at 30 mph. But the shift from
    the first stage to the second stage of the supercharger, which occurred at
    about 17,000 feet, was an abrupt lurch, like downshifting your car from 4th
    to 3rd at 60 mph. Sometimes the supercharger would hang up and not shift
    when it should, which could be a real problem in combat.
    The best solution to high-altitude performance in a piston engine was the
    exhaust-gas-driven turbo-supercharger such as was used in the P-38 and P-47
    (plus the bombers and transport aircraft, including postwar piston jobs
    like the Constellation and DC-6). It maintained sea level horsepower right
    up to 35,000 ft. and more. But it took up a lot of space and I doubt the
    P-51 had room for it. Then again, the XP-37 variant of the P-40 airframe
    was equipped with a turbo-supercharger. It was mounted under the engine.
    And the P-39, a smaller plane than the P-51, was originally equipped with a
    turbo-supercharger. The go-ahead to equip the P-51 with the Merlin may
    have been a logistical one. Packard had built a factory to produce Merlin
    engines and there was no airplane to put them in. The Allison was being
    used by the P-38, P-39 and P-40, and GE was at capacity producing
    turbo-superchargers, so the suggestion to put the Packard-built Merlin with
    its associated mechanical supercharger into the Mustang, where it fit
    neatly with no major re-engineering needed, must have been a very welcome
    one merely from a production point of view. The boost in performance the
    Merlin gave the Mustang was an unlooked for plus.

    The P-40F was equipped with a Packard Merlin, mainly because of a shortage
    of Allisons. It's performance was about the same as Allison-powered P-40s,
    suggesting that the airframe was the limiting factor in improving the
    Curtiss fighter's performance. That the P-51's performance jumped so much
    when the Merlin was installed is an indication of just how advanced its
    airframe was.

    The P-51 (C.C. Jordan; CDB100620)
     
  2. drgondog

    drgondog Well-Known Member

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    Seesul - you suppose he didn't like the Mustang? LoL. Too many things to comment on within one reply.

    As with any persons' perspective about the dastardly Mustang there is a kernal of truth but this narrative is riddled with exagerations.

    First, when the 51B-1 came to ETO in November, 1944 it was the first production model and it did have issues. Don Blakeslee led the first Pioneer Mustang combat mission and did make that comment on Dec 1, 1943. However, He was the same guy that begged Kepner to give him the Mustangs that the 355th FG had just received, so that he could lead the 4th on the first Berlin missions. When Kepner pointed out that his 4th was not yet checked out in them, Blakeslee promised they would qualify on the way to Berlin.. which is kind of wht they did, having flown their first two missions before that with most pilots having less than 1 hour in the 51.

    Secondly, in all the 8th AF transitions (i.e 4th, 355th) from P-47 to P-51 the ground crews were working double duty keeping the 47s operational while learning the 51. Not so, the P-47 and P-38 Groups (except 4th which converted from Spit) The B-1's were experiencing all the problems named from radio interferences with mags, to heating issues in cockpit to gun jams and had an occasional tail lost, wheel drops in high G pullout and even faulty heat treatment of engine bolts. This was a real problem for about 60 days.

    On the other side, the 4th scored more in two weeks of missions with the P-51 in March than they scored in December, January and February in P-47s.

    Contrast that to P-38 effectiveness, and the 4th scored more in the first two weeks of March than all the P-38 scores in the 20th AND 55th period to date!

    The abort rate was slightly higher for the Mustangs in first three months of ETO Ops than either the P-38s or P-47s. One reason is they were flying six hours instead of 2-4hour mission. The 8th AF was sorting out the new P-47C which had a host of gestation problems in April-July 1943 and the P-38 was a nightmare!

    To the structural issues. Problem number one. USAAF dive manuever tactics of dive with rudder and aileron use for evasion put lateral loads on the Mustang w/Merlin that was not accounted for in the tail design from original spec for XP-51/Allison. Beefed up horizontal stabilizer and main spar on the rudder - problem solved... but still an 8g design/12 G ultimate - over stress that and you are still dead -as with every other fighter..

    Wheel uplock failure on High G pullout - leading to ripping off wing with huge drag loads in pull out. Re-design Wheel lock uplock kit - problem solved.

    Cg problems with full 85 gallon fuse tank. Change SOP to burn 60 gallons before switching to external wing tanks. Problem Solved.

    The P-51 gives excellent warning to a stall, but not a lengthy one, when running out of airspeed - or extreme rudder deflection in low speed/High G flight. Learn your airplane and behave accordingly - problem solved.

    4 Gun slanted mount guns jamming. Better QC during ammo linking/belting process/install drive motor and improve gun heating - problem Mostly solved but six gun vertical mount solved the problem.

    and so on
     
  3. seesul

    seesul Active Member

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    thx Bill!
    I´ve never seen anyone speaking about weaknesses of the P-51 on this forum or maybe I haven´t seen other thread speaking so I´m happy we can speak about it here...and it is not because I hate P-51. Be sure that I love this bird...look at my avatar...
     
  4. drgondog

    drgondog Well-Known Member

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    Seesul - great airplane - not perfect. I wasn't 'offended' but I know a lot of facts about this bird and I have flown it. having said this, like all great aircraft it had its flaws, but still a wonderful ship.
     
  5. seesul

    seesul Active Member

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    Bill, could you post some pics of you in or with P-51?
    And how did you get the chance to fly it?
     
  6. MikeGazdik

    MikeGazdik Member

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    I forget who it was that said this, it was quoted in the Martin Caiden book "Fork Tailed Devil". It was a commander in Africa speaking about the P-38, when it was still having teething troubles.

    " I would rather have an airplane that goes like hell, and has a few problems with it, than an airplane that doesn't go like hell ,and has a few problems with it"

    I think this could also apply to the Mustang.

    Both great airplanes once fully developed. Everything with wings had some type of development trouble. But Seesul is right, you don't see as much about the troubles the Mustang had to go through to become one of the greatest.
     
  7. drgondog

    drgondog Well-Known Member

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    Seesul - all my experience was in the 1960-61 timeframe and my father was not big on cameras.. I was still in high school.

    The USAF had an auction on the last of the National Guard ships and my father was lucky enough to get one very inexpensively along with a zero time engine. He traded the engine to Cavalier (I think) in return for a two seat trainer config to replace fuselage tank.

    I learned to fly in a cessna 140 and got back seat transition time in AT-6 , then solo, as wellas a lot (~100 hours) back seat time in the 51, then solo'd and got another 56.5 hours single time plus more with my father in front seat.

    Wish we had kept it.

    He sold it for a lot more than he paid for it in 62 when we moved to Florida from Los Angeles. It was pretty expensive to operate even in those days
     
  8. FalkeEins

    FalkeEins Member

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    Roman, there is a saying about the P-51 which just about sums up the type's 'weaknesses';

    "..The P-51 couldn't do what the Spitfire could do, but it could do it over Berlin.."
     
  9. HoHun

    HoHun Active Member

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    Hi Seesul,

    >In contrast, they sang about the Lightning:

    >"The P-38 is some machine,
    >The answer to a flyer's dream.
    >She'll dive, loop and climb
    >And turn on a dime.
    >To every pilot, she's the queen."

    This page features quite a different version of the song text ... search for (or browse down to) "Give me Operations":


    View: https://www.youtube.com/watch?v=S4Y43aH9xx0

    Regards,

    Henning (HoHun)
     
  10. peril

    peril New Member

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    Yes Hohun, I thought of that too, what about the issues with compression and roll rates.

    P38 is NO dream boat either ;) hehehe.
     
  11. seesul

    seesul Active Member

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    Hi Neil,

    good to see you here. That sentence makes a sence...
    I love both those planes, I mean both P-51 and P-38.
    I´m sad I hadn´t chance to see P-38 in Duxford last year.
    On youtube I´ve seen a P-38 cash in Duxford in 90´s. Were you there back then?
     
  12. seesul

    seesul Active Member

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    I´ve seen that song.
    It´s like with girls...someone loves blondies, someone brunettes...I always loved brunettes and got married a blonde:lol:
     
  13. drgondog

    drgondog Well-Known Member

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    I loved them all - same with 51, 109 and Spit
     
  14. seesul

    seesul Active Member

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    And you´re not the only I guess8)
     
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