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Hello everyone. I’d like to suggest an interesting Mustang prototype for the U.S. tech tree - the XP-51. The XP-51 was essentially a British Mustang Mk.I repurposed for testing, with two examples acquired by the USAAC in 1941. Their evaluation directly opened the development of both the P-51 Mustang and the A-36 Apache production models.
Personally, I feel the XP-51 would make an excellent premium aircraft or Battle Pass reward, as it’s a historically significant prototype that represents the bridge between British and American Mustang development.
History
BackgroundBefore 1940, Great Britain urgently required large quantities of military equipment, with fighter aircraft being a top priority for the nation’s defense. Just before the fall of France, representatives from the Anglo-French Purchasing Commission traveled to America seeking additional P-40s from Curtiss. However, Curtiss’ production facilities were already operating at maximum capacity. This situation prompted the British delegation to approach North American Aviation with a proposal to manufacture P-40s under license.
Dutch Kindelberger, president of North American Aviation, considered but ultimately rejected producing another company’s design. Instead, he proposed developing an entirely new fighter that would outperform the P-40 while utilizing the same Allison V-1710 engine. This was particularly ambitious since North American had no prior experience designing fighter aircraft and promised to deliver the new plane within 120 days.
The resulting NA-73 design was formally proposed in January 1940 for the production of 320 aircraft. After review, the British Purchasing Commission approved the design on April 24, 1940. From initial sketches made in a New York hotel room, the first NA-73X prototype was completed by September 9, 1940, just 127 days later. Following ground tests, the aircraft successfully took flight on October 26, 1940.
The production version, designated Mustang Mk.I, incorporated several design improvements over the prototype. The first operational model rolled off the assembly line on April 16, 1941, with its maiden flight occurring one week later. Flight tests confirmed the Mustang’s superiority over the P-40, and by April 1942, the RAF declared their Mustangs combat-ready.
USAAC ProcurementContrary to some accounts, the US Army Air Corps showed early genuine interest in the design of the British Mustang. When Lieutenant Benjamin Kelsey, an aeronautical engineer and USAAC official, learned of the British contract on May 4, 1940, he arranged for two aircraft from the initial production batch to be diverted for testing at Wright Field. Kelsey recognized the significance of the NA-73’s laminar flow wing design. Consequently, the fourth and tenth production Mustang Mk.Is were reallocated as XP-51 test aircraft, arriving at Wright Field in August and December 1941, respectively.
Testing officially occurred between October 8 and December 22, 1941, though weather and scheduling delays slowed the process. The XP-51 demonstrated exceptional performance at low-to-medium altitudes, outperforming the P-40 and receiving enthusiastic praise from test pilots.
Both XP-51s retained the British Mustang’s armament configuration initially, three machine guns per wing plus two nose-mounted .50 caliber guns, though with American equipment standards. The second prototype later received an experimental Bendix Corporation automatic gun charging system and was sent to Eglin Field for weapons testing, where four 20mm cannon were eventually selected for what would become the first P-51 production model.
Today, only one XP-51 (41-038) survives. After being transferred to the Smithsonian Institution’s National Air and Space Museum and undergoing restoration in 1976, it now resides at the EAA Aviation Museum in Oshkosh, Wisconsin, registered as N51NA.
Specifications
North American XP-51 MustangGeneral Characteristics
- Crew: 1 (Pilot)
- Dimensions:
- Length: 32 ft 3 in (9.8 m)
- Height: 12 ft 2 in (3.7 m)
- Wingspan: 37 ft 0.5 in (11.29 m)
- Wing Area: 233 sq ft (21.6 sq m)
- Propeller:
- Type: Curtiss Electric 3-blade propeller
- Diameter: 10 ft 6 in (3.2 m)
- Powerplant:
- Engine: Allison V-1710-39
- Supercharger: Single-speed, single-stage
- Power Output:
- War Emergency: 1,490 hp (1,111 kW)
- Takeoff: 1,150 hp (857 kW)
- Normal: 880 hp (656 kW)
- Internal Fuel: 170 US gal (644 L)
- Weight:
- Empty: 6,275 lb (2,850 kg)
- Gross Weight: 7,934 lb (3,600 kg)
Performance
- Power-to-Weight Ratio: 0.145 hp/lb
- Max Speed at Altitude: 382 mph (615 km/h) @ 13,000 ft (3,962 m)
- Wing Loading: 34 lb/sq ft (166 kg/sq m)
- Service Ceiling: 30,800 ft (9,388 m)
- Range: 750 miles (1,207 km)
Armament
- Guns:
- 4 x 0.50-cal. machine guns (300 rpg; 1,200 rds total)
- one in each wing and two mounted in the nose under the engine
- 4 x 0.30-cal machine guns
- Outboard pair: 814 rounds per gun (1,628 rds total)
- Inboard pair: 932 rounds per gun (1,864 rds total)
- Total Ammo: 3,492 rds
Cockpit
- Air Publication 2025A - Pilot’s Notes Mustang I Aeroplane Allison V-1710-F3R Engine (September 1941)
- P-51 Mustang in Detail & Scale - D&S Vol. 50 - Part 1 Prototype Through P-51C (1996)
- P-51 Mustang in Action - Aircraft No. 56 (1981)
- P-51 Mustang in Action - In Action No. 211 (2008)
- North American P-51 Mustang - Crowood Aviation Series (2009)
- Allison-Engined P-51 Mustang - Osprey Air Vanguard #1 (2012)
- North American Aviation XP-51 Mustang | This Day in Aviation
- P-51 Mustang Variants - XP-51s - MustangsMustangs.com
- North American XP-51 Mustang
- North American P-51 Mustang - Wikipedia
- North American P-51 Mustang variants - Wikipedia