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The Making of the Mustang

July 6, 2010

One of the great joys of building models is the chance to delve into the histories of the machines themselves, which I’ve often found enhance my understanding or appreciation of the greater historical context in which they operated. With each new kit that I start, I plan to offer a brief history of the aircraft in question.

The North American P-51 Mustang is one of the most widely-recognized aircraft in the history of aviation. It was one of the preeminent fighters of World War II and, depending on who you talk to, the single best piston-engined fighter ever built.

But it didn’t start out that way. There was no massive bidding process or prototype competition, as exists today. In fact, the Mustang was more or less designed on a whim, and improved through a series of happy accidents that would sound contrived if they weren’t true.

The Mustang has its origins in the Lend-Lease program between Britain and the United States. Shortly after the war began in 1939, the Brits set up a purchasing commission to, among other things, organize the manufacture of American fighter aircraft for the RAF.

Just one problem. In 1939, our fighter arsenal wasn’t what you would call stellar. The only U.S. aircraft that even came close to meeting the Brits’ requirements was the Curtiss P-40 Tomahawk. And the Curtiss plant was already running all-out.

Curtiss P-40

Casting about, the British approached North American Aviation about using some of its underutilized production capacity to license and build the P-40 for the RAF.

And this is where it gets awesome.

Instead of agreeing, North American’s president, “Dutch” Kindelberger, promised he could deliver a better aircraft, with the same engine, in less time than it would take to set up P-40 production. The Brits were game, and on April 24th, 1940, signed a contract for the design and production of a new fighter that would be armed with four .303 machine guns and powered by the same Allison engine as the P-40.

North American went to work on the new fighter, incorporating several new principles such as a laminar flow wing to reduce drag and a lightweight, all-aluminum fuselage.

In early August, just 117 days later, the NA-73X prototype rolled off the factory floor. 117 DAYS. Think about that for a minute. That’s about four months, give or take. Four months to design and build a working, flying fighter.

178 days after the initial order, the NA-73X flew for the first time. It handled well and was quickly shoved into production, with the stipulation that North American hand over two examples to the USAAC for evaluation.

The new Mustang (the USAAF tried to christen it the Apache, but the British name stuck) soon demonstrated the advantages of its aerodynamic design by easily besting the P-40 and, surprisingly, the vaunted Spitfire in terms of speed.

But this early Mustang had one glaring flaw. While it performed beyond all expectations at low altitudes, the supercharger fitted to its Allison engine completely gutted out above 15,000 feet. In a war where air combat was taking place at increasingly higher speeds and higher altitudes, this limitation effectively crippled the Mustang Mk. I and the P-51A as fighters, and relegated them to reconnaissance and ground-attack roles when they began entering service in May 1942.

The Allison-engined P-51A

At around the same time as the Mustang was gearing up to enter service with the RAF, a few people from Rolls-Royce were invited to poke around. In true Tim Allen fashion, they quickly realized the solution to the Mustang’s high-altitude woes: MORE POWER. Specifically, the fabulous Rolls-Royce Merlin 61 engine that powered the Spitfire. The Merlin boasted a two-speed, two-stage supercharger better equipped to deliver power at higher altitudes.

Five Mustangs were converted over to the new engine, along with a Rotol propeller off the Spitfire Mk. IX. The improvement was pretty much ridiculous. The fabbed-up Mustangs reached a top speed of 433 mph at 22,000 feet and could operate as high as 40,600 feet.

The Mustang’s high-altitude woes were a thing of the past. Work began at once on a new Mustang, utilizing a licensed version of the Rolls-Royce Merlin 61 called the Packard V-1650. At the same time, the newly-designated P-51B Mustang stole bits and pieces from earlier models and shifted to four wing-mounted Browning .50 caliber machine guns.

The new Merlin-powered P-51B (and the built-in-Dallas P-51C) brought something else to the table, too. Range. Between the slick aerodynamics, the new engine, a large internal fuel capacity, and the addition of two 75-gallon drop tanks, the Mustang boasted a combat radius of nearly 900 miles.

Up to this point, the Allied bombing campaign had been suffering horrific losses, due in large part to the lack of a fighter with the range to escort the bombers all the way to the target area. Imagine a football team, where the offensive line could only advance as far as the thirty yard line before having to turn back for Gatorade. That’s pretty much what was going on, except instead of safeties and linebackers, it was flak and German interceptors.

P-51B Mustang

The Mustang single-handedly changed the equation. Capable of escorting the bombers all the way to and from their objectives, the P-51 helped roll back bomber losses starting in late 1943, and basically made the continuation of daylight raids possible.

In mid-1944, the definitive Mustang variant, the P-51D, started to arrive in Europe, but that’s a story for another post.

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