17. A Brainstorm That Transformed an OK Fighter Into the Greatest One
Eventually, a British test pilot had the bright idea of replacing the P-51’s stock engine with the Rolls Royce engine used in the Spitfire IX. The results were immediate and dramatic. The new engine allowed the Mustang to realize its potential, and transformed it from a mediocrity to the war’s best fighter. From a 390 mph top speed, the Rolls Royce Mustang zoomed to 440 mph, and later models reached 490 mph. From an effective ceiling of 15,000 feet, the improved Mustang soared to 42,000 feet. The test results were passed on to the Americans, and converted Mustangs, equipped with the Rolls Royce engine and now designated the P-51B, began to roll out of factories in June, 1943.
By late 1943, P-51s were in place and ready for action in Europe. When they entered action in 1944, they broke the Luftwaffe’s back. German Messerschmitt Bf 109s had good engines that performed well at the high altitudes in which the bombers flew. But to actually down the rugged B-17 and B-24 heavy bombers, the 109s needed to be fitted with heavy armaments. The problem was that the addition of heavy armaments to the Bf 109s’ light airframe negatively impacted their performance. It made them vulnerable to the bombers’ escorting P-51s, unencumbered by heavy armaments, and armed and optimized instead for the task of ending fighters.
