by Tommy H. Thomason

Saturday, June 11, 2011

Seahorse

The U.S. Navy's involvement with liquid-cooled engines lasted long after air-cooled engines replaced them on its carrier-based fighters. Click HERE for a summary history and more information on the this entry's topic.

In mid 1944, the Bureau of Aeronautics asked North American to submit a proposal for a navalized P-51 Mustang. The resulting NAA-133 was based on its P-51H and to be powered by a Merlin V-1650-11 engine. The wing was redesigned to increase the wing area by 10 square feet (an increase in wing chord of about three inches since the wing span was not changed), substitute larger and slotted flaps, and incorporate wing folding. The ailerons were enlarged and hydraulically boosted.

The landing gear was strengthened and an arresting hook and catapult hook added.
The fin and rudder shown in dotted lines are in accordance with the relatively crude North American three view provided with the NAA-133 proposal. The overall fuselage length and fin height are in accordance with the dimensions on that drawing so it may be that the fin and rudder were raised as shown but I can't be sure that the chord of either the fin and rudder are correct.

The Mustang’s fuselage fuel tank was deleted and the wing fuel capacity was reduced to 150 gallons. The elimination of the fuselage tank allowed for a smaller horizontal tail while maintaining adequate longitudinal stability. The reduction in internal fuel capacity was to be offset by the addition of 50-gallon tip tanks when required.

There is a drawing on the interweb that shows the wings folded to a vertical position rather than continuing past vertical to reduce overall height. It also shows the tail wheel door extending aft to the rudder post. I don't have any corroborating information as to either detail.

The P-51H fin height was increased shortly after production began and presumably the same change would have been incorporated on a Navy Mustang.

There is an excellent P-51H kit available from Czech Master Resin:
It includes both the original and taller tail. Click HERE for a review.

A similar conversion to represent the P-51D carrier trials airplane could be made from any P-51 kit.

This is the illustration from my very first Tailhook Topics column for IPMS USA, which appeared in the Update, Volume 16 No.2:
No Bureau Number or "Navy" appeared anywhere on the aircraft in the few pictures which have been published. The aircraft retained the .50 caliber guns and wing bomb racks during the carrier trials. The tail hook was attached just aft of the tail wheel well with the hook point just behind the rudder post. The bottom of the rudder appears to have been just slightly cut out for the hook point.

An even rarer P-51 was operated by the Navy as BuNo 57987. It was Army Air Force Serial No 41-37426, one of a production lot of Mustang Mk 1As that were to be delivered to the RAF, many of which were taken instead by the Army Air Force.
Note that the inlet to the belly air scoop has an opening that can be varied in area.

5 comments:

  1. I hope you don't mind but I posted a link to your article over at the P-51 SIG.

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  2. Not a problem. I'll check the SIG to see if anyone has comments or corrections and then revise this entry accordingly.

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  3. There were actually two projects, the first involving a P-51D. Later, North American submitted NA-133, a lightweight P-51H variant, and tried it again.

    R. Lewis

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  4. If you're referring to the P-51D evaluation aboard Shangri-La in November 1944, I'm pretty sure that it was in support of the NA-133 evaluation by BuAer. See http://thanlont.blogspot.com/2011/06/navy-and-liquid-cooled-engines.html

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  5. Regarding the P-51 transfered to the USN (AAC 41-37426/BuNo 57987, ex RAF FD524), it was from a batch converted with provisions to mount two K24 cameras. Were these fitted to the navy aircraft? And to what evaluation purpose was the aircraft put by the navy? Also, did this aircraft retain the 4X20mm cannons?

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