Dingo,
The P-51A had the Allison V-1710-81 (F20R) engine rated at 1200 hp for takeoff and 1125 hp at 18,000 feet, with significantly better high-altitude performance than the V-1710-39 of the P-51. The engine was fitted with a new supercharger which further enhanced low-altitude performance. In addition, a larger-diameter propeller was fitted. Maximum speed rose to 409 mph at 11,000 feet, faster at medium altitudes than any other fighter then in service.
P-51A PERFORMACE: One 1200 hp Allison V-1710-81 twelve-cylinder Vee liquid cooled engine. Performance Maximum speed was 340 mph at 5000 feet, 360 mph at 10,000 feet, 380 mph at 15,000 feet, and 390 mph at 20,000 feet. Range on internal fuel was 750 miles at 300 mph at 10,000 feet. Range with two 125 Imp. gall. drop tanks was 2000 miles at 266 mph and 2350 miles at 228 mph. An altitude of 5000 feet could be attained in 2.2 minutes, 10,000 feet in 4.4 minutes, and 20,000 feet in 9.1 minutes. Service ceiling was 31,350 feet. Weights: 6433 lbs empty, 8600 lbs normal loaded, and 10,600 lbs maximum loaded. Dimensions: Wingspan was 27 feet 0 1/4 inches, length was 32 feet 2 1/2 inches, height was 8 feet 8 inches, and wing area was 233 square feet. Armament: Four 0.50-inch machine guns mounted in the wings. The inboard pair had 350 rpg and the outboard pair had 280 rpg. An underwing load consisted of two 250 lb, 325, or 500-pound bombs.
Initially, the P-51B had the Packard V-1650-3 engine rated at 1400 hp for takeoff and 1450 hp at 19,800 feet and carried four 0.50-inch machine guns with a total of 1260 rounds.
P-51B PERFORMANCE: One 1620 hp Packard Merlin V-1650-3 twelve cylinder Vee liquid-cooled engine. Maximum speed was 388 mph at 5000 feet, 406 mph at 10,000 feet, 427 mph at 20,000 feet, 430 mph at 25,000 feet, 440 mph at 30,000 feet. Range on internal fuel was 550 miles at 343 mph at 25,000 feet, 810 miles at 253 mph at 10,000 feet. With maximum external fuel, maximum range was 2200 miles at 244 mph. An altitude of 5000 feet could be attained in 1.8 minutes, 10,000 feet in 3.6 minutes, 20,000 feet in 7 minutes. Service ceiling was 42,000 feet. Weights were 6840 lbs empty, 9200 lbs normal loaded, 11,200 lbs maximum loaded. Wingspan was 37 feet 0 1/4 inches, length was 32 feet 3 inches, height 8 feet 8 inches, and wing area was 233 square feet.
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