The P-51 Mustang
The secret to controlling the ground turned out to be controlling the air. The Allied success relied heavily on the long-range P-51 Mustang fighter, enabling the resumption of strategic bombing after heavy losses suffered by unescorted bombers in 1943. American warplanes of the highest caliber throughout the conflict were those built for export to Britain and then converted by the British to employ the Rolls-Royce Merlin engines.
The first P-51B/C Mustangs with Merlin engines saw action in Europe in December 1943. The US bombing campaign against Germany greatly benefited from the long-range, high-altitude escort these P-51s provided. The P-51D became the main long-range escort fighter for the USAAF when it began to arrive in large quantities in Europe in the spring of 1944.
Owing to its exceptional performance in long-range escort duties, the Mustang became the pioneer single-engine aircraft stationed in Britain to breach Germany’s defenses, reach Berlin, and go with heavy bombers over Romania’s Ploiesti oil fields. How did the legendary Mustang manage to carry out these kinds of lengthy escort missions? Not because of its drop tanks.
The secret behind P-51B/C/D Mustang range
‘Lots of planes could carry drop tanks: P-47, P-40, P-38, etc.,’ says James Gibson, former MP&P Engineer at Boeing, on Quora.
‘The real secret to the Mustang’s range was not the laminar flow control wing, or the Merlin engine. It was the addition of a fuselage tank behind the cockpit halfway through production of the P-51B. This additional internal tank increased fuel capacity by 85 gallons; the original P-51Bs only had 184 gallons in the wings. The addition increased total fuel to 269 gallons, or some 30%. Further adding two 75-gallon drop tanks, you reached 419 gallons. The later D&H models carried 110 gal drop tanks for 489 gallons.
‘But when you carried so much fuel, you had to be aware of which tanks you were using at which point in the flight. On take-off, you used the rear fuselage tank. This tank effected the center of gravity of the plane. You didn’t want to tangle with a 109 or a Focke Wulf when carrying fuel in the rear tank. So you burned it first and then switched to the drop tanks about halfway to Berlin.’
Gibson concludes;
‘You would then burn off the drop tanks, hopefully before engaging enemy fighters. But if they struck early you could drop those tanks and thus be clean and maneuverable. This was the fight profile that allowed the Mustangs maximum range and best performance when over target.’
Photo by U.S. Air Force