P-51 H (Mustang V)

Getting there: XP-51F, G & J

Final result: the P-51H

Design changes

Production

Too late for combat

Specifications

Serial numbers

 

 

Final result: the P-51H

The Packard Motor Car Company had done its own development on the Rolls Royce Merlin engine and came up with the
V-1650-9 version. It was capable of delivering a war emergency power (WEP) of 1,900 hp at 20,000 ft. Packard said they could deliver the new engine in late 1944 and so this engine was chosen to power the next production Mustang: the P-51H.

The ultimate and last mass produced Mustang was a result of several lightweight prototypes, the XP-51F, XP-51G and
XP-51J. The USAAF decided to commit to the Packard V-1650-9 powered P-51H instead of committing to the earlier lightweight prototypes which were not regarded as entirely practical for combat use. The P-51H wore NAA designation
NA-126 and was as far as design is concerned closest to the XP-51F. It was ordered into production in June of 1944 and was to be the main fighter for the invasion of Japan . An order of 1,000 P-51H Mustangs was approved on June 30th, 1944.

 

Design changes

The P-51H differed a lot from the P-51D, so practically no parts from the P-51D line were usable in the P-51H. Most noticeable changes in design were:

 

  • The wing had a straight leading edge, so the famous leading edge kink of the D-model was removed. The wing also had a new aerofoil with an even newer low-drag laminar flow profile.
    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications
  • Smaller landing gear and wheels.
    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications
  • The wheels had new disc brakes.
  • A taller tail to deal with lateral stability problems.
  • The fuselage was a bit more slender and length increased by two feet to 33.33 ft.
  • The belly scoop inlet profile was not angled any longer but square like the first P-51s.
    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications
  • The oil cooler was removed from the radiator group, removing the long and vulnerable oil pipes. The oil passed through a heat exchanger mounted on the front of the oil tank and next to the engine intercooler. The flow of glycol carried away the heat from the oil.
  • The chin scoop was decreased in size.
    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications
  • The engine mounts were incorporated into the structural engine cradle, saving weight.
  • The engine was a Rolls Royce Merlin V-1650-9, featuring a water-methanol injection for power boost with a WEP to 2,200 at 10,200 ft
  • The propeller was an 11'1" four-blade Aeroproducts propeller. The blades are wider and keep approximately the same width over almost the whole blade. It also has rounded tips.
  • Armament was the same as the P-51D, but now had removable ammo boxes and a redesign of the ammo doors to save time reloading and scratching of the wing. Rounds were 1,880 total.
  • Fuel in the fuselage tank was decreased to 50 gallons, the total internal fuel capacity was 255 US gallons.
  • The canopy was redesigned and saw the “hump” moved forward. The pilot sat higher for a better 8° deflection angle using the gunsight.
    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications
  • The cockpit panel was improved and simplified.
  • The fuselage skins were lighter and thinner.

All these changes made the P-51H the fastest production mustang with a top speed of 487mph (784 kph) at 25,000 ft (7,600 meters).

Photo by NAA

 

Production

The P-51H first flew on February 3rd , 1945, piloted by Bob Chilton. This P-51H-1NA (44-64160) was wrecked just three days later when the prop failed.

Nevertheless, production began as it was to complement the P-47N as the lead fighter in the invasion of Japan . The USAAF ordered 2,000 examples of the P-51H.

The H-model did not start out as the “tall tail Mustang”. The first 20 P-51H-1NAs were built with the normal D-model tails. These were later retrofitted with the taller tails. The taller tails were incorporated into production H-models starting with the
P-51H-5NA block.

As with previous P-51s, both production facilities of NAA would be used. The P-51H versions built at Inglewood were designated NA-126 and NA-129 (known as P-51L, it was the same as the NA-126 but with minor differences and a new Merlin V-1650-11 engine). The order was for 555 NA-126s and 1,445 NA-129s. The H-models at Texas were given designation NA-124 (P-51M) and had the V-1650-9A engine and a Hamilton Standard propeller.

Production continued and 221 P-51Hs (20 -1NAs, 280 -5NAs and 255 -10NAs) were delivered by July 30th and 370 by VJ Day in early September.

Photo by USAF

 

Too late for combat

Because of the end of the war, orders for 1,445 more were cancelled and production was cut short. Only 555 of the P-51H (NA-126 batch) versions were built at Inglewood and only one single P-51M rolled out of the Texas plant (45-11743). All other unfinished airframes were scrapped.

One P-51H was given to the RAF for evaluation (KN987)

The P-51H was delivered to some units in the Pacific before VJ Day, but not a single one actually saw any combat action. In the later Korean war, the heavier and stronger D-models were preferred over the H-models.

Only 5 P-51Hs survived, 2 are display quality only, 2 are airworthy and the last is in restoration to be airworthy. One of the XP-51G prototypes does exist and is in a long term restoration with John Morgan in California . This G model was saved by chance and fast action while on its way to the scrapper.

Photo by Victor G. Archer

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