P-51D-20NA: What does the "-20NA" mean?

Discussion in 'Aviation' started by Max89, Oct 28, 2014.

  1. Max89

    Max89 Member

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    I'm a little confused over what the "-20NA" means in P-51D-20NA. Also, what is NA-122? I've seen both of these terms used in a lot of places, but there's no explanation given as to what they mean.
     
  2. Denniss

    Denniss Active Member

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    NA-122 is an internal manufacturer designation, -20 is the build lot number and NA should be the desination for the manufacturing plant (NA = Inglewood, California, NT= Dallas, Texas).
    See also USAAC/USAAF/USAF Fighter Designations
     
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  3. drgondog

    drgondog Well-Known Member

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    Denniss is correct.

    NA 122 was let 3-11-44 and served to fund the P-51D-20, -25 and -30NA for a total of 4000 P-51D's. 130 of the -20NA block were delivered to RCAF
     
  4. Max89

    Max89 Member

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    So that "P51D" at the start of the build lot/block number is a USAF designation, correct? Also, given that all -20NA, -25NA, and 30NA had the same internal manufacturer designation, does that also mean that all aircraft from these block were built to the exact same specification?
     
  5. GrauGeist

    GrauGeist Well-Known Member

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    How it breaks down:

    P - status or mission type: "P" stands for "Pursuit"
    51 - US Army assigned series number given when the type was accepted
    D - sub type, meaning as the type was improved, it was given a suffix (A, B, C, D, H, K, etc.)
    -20 - is the lot number given (as noted above) for the series of production
    NA - where the aircraft was produced (as mentioned above)
     
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  6. GregP

    GregP Well-Known Member

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    The "D" is a major change. The "-20" or "-25" is a minor change.

    The difference is a major change meant the mechanics would have to get formal training. A minor change meant they could cover the differences in a published tech order, and the mecahnic could read about and implement the minor changes themselves.

    For instance, the change from the Allison to the Merlin necessitated formal training on a completely different engine and propeller/constant-speed system (electric to hydraulic). Think P-51/P-51A to P-51B/C and onward. But no change or a change from one radio to another that had the same hookups plus or minus a few wires could be covered in publications that the mecahnics could read and implement without formal classes.

    So, if it affected a system or a major subassembly, it was a new letter variant. If it was no change or if it affected only minor fitment change between lots, it was a new dash number. New dash numbers were mostly, but not always in increments of 5 ... like -20 to -25. Sometimes they did it in incerments of only 1 or 2, seemingly just to be different or to indicate a REALLY mionor improvement, such as increasing the current to an electric heater by 3% or changing the paint from semi-gloss to flat matte with the same color.

    These data come from both reading and from 10 years of listening to WWII vets give talks about our planes that they flew in WWII. This Saturday features the F4U Corsair and we have two former WWII Corsair combat pilots giving a talk on their experiences. We will then fly our F4U-1a for the crowd. I say "we" but I am not a warbird pilot ... I mean the Planes of Fame Museum, not "me."
     
  7. Shortround6

    Shortround6 Well-Known Member

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    I believe the "plan" was that by leaving 4 numbers unused (-20 to -25, leaves -21,-22,-23,-24) it would leave room for "field" modifications or modifications after the plane rolled out of the factory. I don't think this was ever really followed up on though, or at least in any consistent manor.
     
  8. drgondog

    drgondog Well-Known Member

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    The P-47 and P-38 had many interim 'dash' numbers between major blocks.

    The usual practice was for the 'new/current' design teams working on a new block would incorporate Engineering Orders from the previous block as part of the current design to maximize commonality.

    The P-51D-20 in the third block for example, was the first P-51D to have rocket stubs which was incorporated as an Engineering Change Order and became incorporated into the first block of -25NA and equivalent NT as part of the common BOM, tooling and manufacturing Process Plans.
     
  9. GrauGeist

    GrauGeist Well-Known Member

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    You didn't like my post, Bill? :lol:
     
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  10. Milosh

    Milosh Well-Known Member

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    Max89, tho not perfect this site is fairly good,
    North American P-51D/K Mustang

    from the link:
    Inglewood delivered 6502 P-51Ds, ordered as the NA-109 (D-1 to D-10), NA-111 (D-15 and D-20) and NA-122 (D-15 and D-30). P-51Ds were also constructed in NAA's Dallas plant, the Dallas plant building some 1600 of these planes before production finally ceased. Dallas-built blocks D-5 through D-20 were known as NA-111, with blocks D-25 and D-30 being known as NA-124
     
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