How did my favourite airplane of WW2 become the aircraft that changed the direction of the war? In the fall of 1940, Britain needed America’s help to replenish the fighter inventory after holding off the Nazi Luftwaffe during the Battle of Britain. Limited war production and materials, Britain was unable to replace the lost Hawker Hurricanes and SuperMarine Spitfires fighters lost over the English skies. Both FDR and Churchill identified the Curtis P40 Warhawk as the fighter that the Royal Fighter Command would take delivery of to replace the above. As the Royal Procurement Team arrived in America to order the new planes, Curtis informed them that they were already at capacity delivering planes to the US Army Airforce. However, Curtis did recommend a startup named North American Aviation who might build the P40 under license using their excess capacity.
Upon learning that NA would need months to retool their plant for the P40 came as a great disappointment to the Brits. At this critical moment in history, the head of NA suggested that they could deliver a prototype of their own design within a hundred days. With renewed enthusiasm the Procurement Team indicated that they would order hundreds. The British test pilots determined that the new airframe was light, strong with new laminar airflow wings. However, the American Allison engine with its single supercharger restricted its effectiveness to below 15,000 feet. Undeterred, the Brits would use the plane as a ground support and reconnaissance platform.
Fast forward to 1943 when another British test pilot suggested that marrying the Roll Royce Merlin engine with its dual superchargers would rectify altitude ceiling problems experienced with the Allison engine. Voila! As they say the rest is history. The potential P51 Mustang was unleashed with its operational ceiling reaching 40,000 feet, top speed reached 450 mph at level flight, and an operational range with drop tanks reaching 1,200 miles. The Mustang could now escort the American heavy bombers all the way deep into Germany, conduct combat operations with enough fuel to strafe the Luftwaffe back to their bases and still escort the bombers back to England. Needless to say the P51 Mustang became a game changer. Even Hermann Goerring, Hitler’s Vice Fuhrer, understood the implications after witnessing Mustangs over Berlin; “the gig is up!”
You know all this right! Here’s the lesser known part of the story. Once the US Airforce Generals knew of the Mustang’s capabilities, they couldn’t order enough of them fast enough. However, Rolls Royce people indicated that their English plants were at maximum capacity building the Merlin for British requirements needed in the Hurricanes, Spitfires, and the Lancaster bomber. The RR people did indicate that the Packard Motor company was considered Stateside to build the Merlin under license. Once the Airforce approached the Packard engineers they indicated that it was possible within 18 months getting into production. The Airforce Brass said 6 months reminding them that each bomber had a crew of 10 losing hundreds of bombers on each mission. The Packard organization hit their targeted timeframe within 6 months producing an initial volume of 400 Merlin’s/month.
Just to put this in perspective, the Packard engineers took blueprints in metric and converted 10,000 parts to Imperial measurements to assemble a single engine. These were the plants that gave rise to the famed “Rosie the Riveter” working in war production plants operating 24x7 with relentless quality control. The technicians understood that an improperly installed screw with micro tolerances would cause engine failure over Germany killing its 20 year old pilot. Packard surged to a peak of 800 Merlin’s/month totaling 50,000 engines by war’s end. This was singularly the most important plane engine that defined the Allied war effort.