North American XP-51G Mustang - The Experimental Lightweight Mustang (II)

[Nostalgistic]

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North American XP-51G Mustang

   Hello all! I’d like to suggest the North American XP-51G Mustang for US aviation in War Thunder. It was the second of three experimental lightweight Mustang models evaluated by the US Army Air Forces and the RAF under a joint development program. In short, the XP-51G was developed as a lightweight version of the P-51D to achieve improved performance with the new Rolls-Royce Merlin RM.14.SM engine and an extensively revised airframe. It was arguably the hottest rod of all Mustang variants. Experience gained from evaluating the XP-51G, along with the XP-51F, ultimately contributed to the development of the P-51H Mustang.

History

The success of the early Merlin-powered Mustangs led the Allies to appreciate their superior performance compared to the Allison-powered variants. However, concerns arose over the steady weight growth of the Mustang throughout its development into the P-51D/K models. These newer Mustangs found themselves outclimbed by Spitfires (by approximately 1,200 fpm) and outrolled by the Fw 190, which had nearly twice the roll rate. The RAF first approached North American in January 1943 regarding the possibility of a lightweight Mustang design, with the goal of reducing overall gross weight. This request eventually evolved into a joint program when the Army Air Forces formally initiated the contract and program management.

Three XP-51F prototypes, designated NA-105 by North American, were ordered on January 3, 1943, under MX-356 as the formal US Army project designation, before the first P-51D had even been produced. Consequently, the P-51E designation was skipped and never brought to fruition. In June 1943, the XP-51F contract was amended to include five aircraft (43-43332 through 43-43336) powered by the 1,380 hp V-1650-3. This was later changed to the 1,490 hp V-1650-7 while the aircraft were still under construction. The British also agreed to supply five 1,675 hp RM.14.SM Merlin engines, which would power the final two aircraft of the amended order, designated XP-51G (NA-105A). The RAF requested one example of each model for its own testing.

Work on converting the fourth and fifth XP-51F airframes into XP-51Gs began in January 1944. Designated NA-105A by North American, the XP-51G shared the same radically revised lightweight airframe as the XP-51F. Weight was reduced by eliminating unnecessary structures and equipment, including the fuselage fuel tank behind the pilot’s seat. The wings featured smaller wheel wells, while the landing gear used smaller struts and wheels. The radiator housing was redesigned and blended more smoothly into the aft fuselage, and the oil cooler was replaced by a heat exchanger. A longer bubble canopy reduced drag but required hydraulic operation and seat adjustment mechanisms. The principal differences from the XP-51F were the installation of the Rolls-Royce Merlin RM.14.SM engine and a five-bladed wooden Rotol propeller. The Merlin engines arrived in February 1944 and featured fuel control metering instead of a conventional carburetor. At a critical altitude of 25,000 feet, the engine was capable of producing 2,200 hp using Grade 150 fuel in war emergency power.

The first XP-51G, serial number 43-43335, flew in early August 1944, likely on August 9. Initially fitted with the five-bladed Rotol propeller, the aircraft completed only a brief 20-minute flight before being forced to land. To reduce susceptibility to directional instability encountered in flight, the original propeller was replaced with a more conventional four-bladed Aeroproducts Unimatic A-542-B1 propeller.

Subsequent testing demonstrated impressive performance. The XP-51G had attained a maximum speed of 498 mph at 22,800 feet. However, continued evaluation revealed that the RM.14.SM engine remained troublesome and unsuitable for production. The second XP-51G, serial number 43-43336, was delivered to the United Kingdom for trials under RAF serial FR410, where it was also designated Mustang V. Test flying in Britain continued until February 1945.

Ultimately, no further development was pursued because the RM.14.SM required substantial refinement. Neither the XP-51F nor the XP-51G progressed beyond the prototype stage or entered production. Nevertheless, lessons learned from both aircraft directly influenced the development of the final and most advanced production Mustang, the P-51H, powered by the Packard-built Merlin V-1650-9.

Specifications

North American XP-51G Mustang

General Characteristics

• Crew: 1 (Pilot)
• Dimensions:
  • Length: 32 ft 3 in (9.82 m)
  • Height: 13 ft 8 in (4.17 m)
  • Wingspan: 37 ft (11.28 m)
  • Wing Area: 233 sq ft (21.64 sq m)
• Propeller: 1 x 5-bladed Rotol wooden propeller or 1 x four-bladed Aeroproducts propellers
• Powerplant:
  • Type: 1 x Rolls-Royce Merlin RM-14-SM, two-stage supercharged
  • Power Output: 2,200 hp (2,230.51 PS)
• Fuel Capacity:
  • 180 US-gal (681 L)
• Weight:
  • Empty: 5,750 lb (2,608 kg)
  • Gross: 7,265 lb (3,295 kg)
  • Max. Takeoff: 8,889 lb (4,032 kg)

Flight Performance

• Power-to-Weight Ratio: 0.30 hp/lb (0.67 ps/kg)
• Wing Loading: 32.0 lb/sq ft (156 kg/sq m)
• Max Speed:
  • 470 mph (756 km/h) @ 20,000 ft (6,096 m)
  • 498 mph (801 km/h) @ 22,800 ft (6,949 m)
• Climb Performance:
  • Rate of Climb: 5,882 fpm (29.9 m/s)
  • Time to Altitude: 3.4 minutes to 20,000 ft (6,096 m)
• Service Ceiling: 42,500 ft (12,954 m)

Armament

• Guns:
  • 4 x 0.50-cal M2 Browning machine guns (250 rpg; 1,000 rds)
• Bombs:
  • 2 x 500-lb bombs
• Drop Tanks:
  • 2 x 75 US-gal drop tanks

Images

Related Suggestions

• XP-51
• P-51A-10
• P-51B-1
• P-51B-5 (Malcolm Hood)
• P-51C-10 (Malcolm Hood + Dorsal Fin)
• XP-51F
• XP-51J

Sources

1. Bert Kinzey, P-51 Mustang Part 3: P-51D and Subsequent Variants, Detail & Scale Series Volume 23 (2026)
2. Malcolm V. Lowe, North American P-51 Mustang, Crowood Aviation Series (2009)
3. Bill Norton, US Experimental & Prototype Aircraft Projects: Fighters 1939-1945 (2008)
4. David McLaren, North American P-51H Mustang: Includes Lightweight Fighters XP-51F, XP-51G, & XP-51J, Air Force Legends Number 209 (2003)
5. William Green & Gordon Swanborough, The Complete Book of Fighters: An Illustrated Encyclopedia of Every Fighter Aircraft Built and Flown (2001)
6. Francis H. Dean, America’s Hundred Thousand US Production Fighters of WWII (1997)
7. Robert F. Door, US Fighters of World War Two (1991)
8. F.G. Swanborough, United States Military Aircraft Since 1909 (1989)
9. Enzo Angelucci, The American Fighter: The Definitive Guide to American Fighter Aircraft from 1917 to the Present (1987)
10. P-51 Mustang in Action, Aircraft No. 45, Squadron/Signal Publications (1981)
11. William Green & Gordon Swanborough, World War Two Fact Files - US Army Air Force Fighters Part 2 (1978)
12. William Green, War Planes of the Second World War Fighters Volume Four (1973)
13. WWIIAircraftPerformance.org – XP-51G Performance Curves
14. WWIIAircraftPerformance.org – XP-51G Estimated Performance
15. North American XP-51F, G, J Mustang

Thank you for taking the time to read my suggestion! 😃

[BACKRAGE44428-live]

+1 for the tree

[BasherBenDawg8]

5 blades are clearly better than 4, +1!