- Yes, as a tech tree vehicle
- Yes, as a premium vehicle
- Yes, as an event vehicle
- Yes, as a squadron vehicle
- No, I would not like to see the XP-51F in game.
- Yes, I would
- No, I would not
- I voted no on the first question
Introduction
The story of the North American Aviation P-51 Mustang is a story of collaboration between the United States and United Kingdom, producing one of the most vital fighters for Allied operations in Europe and arguably the best fighter of World War II. The P-51D (Mustang Mk.IV) has cemented itself as a legendary aircraft, but even its designers recognized that it had room for improvement. The continuation of the Mustang saga began with the “Lightweight Mustangs” - the NA-105 prototype aircraft. As the Mustang had begun, so too would it evolve, with collaboration between NAA and Supermarine producing the fastest Mustang variants ever. The ancestor to the P-51H was trialed not only by the USAF but by the Royal Air Force in the form of both the XP-51F and XP-51G. This is the story of how the Mustang reached its zenith - and why the RAF wasn’t interested in it at all.
TL;DR
- High performance redesign of the venerable P-51
- Lighter weight and aerodynamic redesigns provide increased performance
- Reduced armament akin to the P-51C but with less ammo
- Lower wing loading for more agility
- Superior stalling characteristics
- Large, high mounted canopy for better visibility
History
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The history of the P-51 as a whole has further reading readily available, so its genesis does not require too much examination. The Mustang arose from Britain’s purchasing requirements for a new American fighter to supplement British equipment. Outsourcing production in this way would allow the RAF to take advantage of America’s excellent industry while being able to commit their home factories to existing designs like the Spitfire and Hurricane. However, none of the currently available (in the late 30’s) aircraft met British standards. Reluctantly, the British decided to buy some P-40 Tomahawks, but because Curtiss-Wright was using all of its production, they tried to source some license-built versions from North American Aviation. Instead, NAA promised a new fighter aircraft which could outperform the P-40, and after some back and forth on the design details, the P-51 was born.
The Mustang came into an element of its own once Rolls-Royce engineers installed Merlin 65 engines with two-stage supercharger to the five Mustang X prototypes, while NAA for their part installed Packard V-1650-3s (Merlin 61s) in two XP-51Bs. At altitude, the aircraft delivered speed improvements of around 50 miles per hour. Between the excellent high altitude performance and its very good fuel capacity, the USAAF became very interested in the Packard Merlin-powered Mustangs, producing the P-51B, then C, and eventually D variant which had a V-1650-7. However, the Mustang lineage underwent an interesting split even before the XP-51B had left the ground.
The question that prompted the beginning of the “Lightweight Mustang” was simple: why is the Mustang so much heavier than the Spitfire? Despite occupying similar footprints in terms of size, the Mustang was 1,500 pounds heavier empty and the disparity was even larger loaded (due to the Mustang’s greater fuel capacity). When the Spitfire was already struggling to deal with the Focke-Wulf Fw 190, the heavier and less maneuverable Mustang would surely fare no better. Edgar Schmeud, the Mustang’s chief designer, got the idea to create a new Mustang that weighed less while also investigating new engines to produce more power. The combined effect of both of these ideas would be a significant improvement in performance. Upon putting forward a proposal for a new design, known by the company code NA-105, Schmeud secured a contract from the USAF for five prototypes.
The NA-105 would be produced in three versions: the XP-51F, XP-51G, and XP-51J, the latter of which was added later on to test an Allison engine. In order to prepare for production, the NAA design team first had to figure out how to save weight in the first place. To this end, Schmeud visited Supermarine in Britain to examine the Spitfire for inspiration. After Supermarine had weighed the individual parts for the Spitfire, their findings were interesting - because British standards did not require the same structural rigidity as American aircraft, the components weighed less. Other weight savings were introduced by using new aluminum alloy for the plane’s skin, incorporating plastic components, using a thinner wing with redesigned shape, removing the fuselage fuel tank (though the wing fuel tanks were slightly increased in response) and lightening the ammo load to just 250 rounds per gun. In all, despite appearances, the NA-105 might as well have been a new aircraft. These changes resulted in a plane which, while still heavier than the Spitfire, was much closer to its weight than before, with an empty weight in the 5,700 pound range.
Like the Mustang itself, the XP-51F had a rather quick turnaround time. From the approval of the contract in mid-1943, it only took 7 months for the first XP-51F to get off the ground in February of 1944. Due to its significant weight reductions compared to the P-51D, the XP-51F handily outpaced it, achieving a maximum level speed of 466 mph (750 km/h) compared to the P-51D’s 440 mph (708 km/h) despite using a much weaker V-1650-3 compared to the D model’s V-1650-7. In addition, the rate of climb was superior, with a time to 20,000 feet (6,100 m) of 4.9 minutes compared to 7.3 minutes for the P-51D. Maneuverability was enhanced by the lower wing loading, making the XP-51F a clear improvement over the P-51D for short range operations at nearly any altitude. Provision for drop tanks was kept in the event that the plane would be used for escort missions, though the significantly reduced internal fuel capacity would hamper its effectiveness.
The third and final XP-51F was sent over to the RAF at the end of June 1944. However, for one reason or another, they didn’t seem particularly interested, as official testing at Boscombe down was very brief and no real performance data collected. Eventually, it found its way into the hands of Supermarine test pilots who took it for a spin and recorded their results. One glaring issue was that the XP-51F had pretty severe rudder stability problems. Aileron control was also bad at higher speeds, but at low speeds up until the point of stalling control was extremely good. The final major gripe was the inclusion of a seemingly pointless hydraulic seat raising system, along with the canopy being too oversized for its own good. However, there was plenty of praise to go around. The stall speed of 92 mph (148 km/h) indicated airspeed was exceptional, and it was a very pleasant plane to handle at low-medium speeds. In addition, the hydraulically powered sliding canopy would enable pilots to open it and jettison at higher speeds. However, the USAF had no need for a dogfighting Mustang when the P-51D competed well with enemy fighters at altitude and whose main service objective was bomber escort and ground attack. Meanwhile the RAF were pursuing not only high-speed developments and refinements of the Spitfire but jet powered aircraft in the form of the Meteor and Vampire, to which the XP-51F generally compared poorly. Had it been received and tested thoroughly earlier, the XP-51F may have found a British order. Unfortunately, this is another “what if” to add to a long list of aviation industry ventures.
Specifications
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North American Aviation XP-51F
Dimensions:
- Length: 32 ft 3 in (9.82 m)
- Span: 37 ft 0 in (11.29 m)
- Height: 13 ft 8 in (4.17 m)
Weight:
- Empty: 5,634 lb (2,556 kg)
- Loaded: 8,500 lb (3,856 kg)
Propulsion: 1 x Packard V-1650-3 12-cylinder inline engine
- Takeoff horsepower (S.L., 150 octane): 1,400 hp
- Max combat power (150 octane):
- 1,700 hp at 5,750 ft (1,753 m)
- 1,550 hp at 17,750 ft (5,410 m)
Maximum speed: 466 mph (750 km/h) at 29,000 ft (8,839 m)
Ceiling (estimated): 45,000 ft (13,716 m)
Armament:
- Guns:
- 4 x .50 caliber (12.7 mm) AN/M2 Browning heavy machine gun (250 rounds per gun, 1,000 rounds total)
- Drop tanks:
- 2 x 75 gallon (284 liter) drop tanks
Crew: 1
Additional equipment: N/A
Why it should be in the game
The XP-51F would provide an interesting lighter weight version of the Mustang to the British and/or American tech trees. As most of its deficiencies aren’t really an issue in War Thunder, it can be considered an upgrade in nearly every respect to the P-51C despite having a weaker engine. However, pilots would have to be conservative with their ammo as the provisions for 250 rounds/gun are not as ample as other Mustang variants or U.S. planes in general. As I said in the introduction, the Mustang is a story of Allied cooperation and I would personally be happy to see this plane and its cousin, the XP-51G, in both tech trees.
Sources
- The Mustang that might have been
- [2.0] The Merlin Mustangs
- North American XP-51F, G, J Mustang
- THE LIGHTWEIGHT MUSTANG PROGRAMME - Mustang: Thoroughbred Stallion of the Air
- North American XP-51F : North American
- Mustang XP-51F/G/J prototypes | Secret Projects Forum
- Various charts from P-51 Mustang Performance
