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No. 2770:
Building the Mustang

Today, our guest, NASA engineer Fitz Walker, remembers the P-51 Mustang. The University of Houston presents this series about the machines that make our civilization run, and the people whose ingenuity created them. 

The crash of a highly modified World War II fighter plane at the 2011 Reno Air Races was a grim reminder; pushing the limits in any vehicle can be fatal. But lost in that tragedy was the story about vehicle its self — the North American P-51 Mustang fighter, a top-of-the-line combat aircraft from that era, almost universally coveted by aviation fans. In fact, the Mustang prominently appears in Steven Spielberg's movie Red Tails

P-51 in British markings

The Mustang is instantly recognizable with its polished aluminum skin, sleek lines, and squared-off wings and tail. It was a marvel of aircraft engineering. What's surprising, though, is that it was designed not for America, but for the British. While England had an increasing inventory of its own Hurricanes and Spitfires, her intense struggle to repel Nazi Germany's air forces during the Battle of Britain depleted the supply. England needed every aircraft she could find. So, she looked to the then neutral United States for more.

The British commissioned North American to develop a new fighter aircraft. Known at the time for the T-6 Texan trainer and the multipurpose B-25 medium bomber, North American designers and engineers went from conceptual design to flying prototype in just four months. An incredibly fast engineering feat then and something almost impossible to do now. And the engineers were even able to include revolutionary features and leading edge technologies into the design.

Texan trainer

The wings, for example, used advanced airfoil technology developed by the National Advisory Committee for Aeronautics. That agency, NACA, would later be merged and transformed into a more well known entity: NASA. Engineers placed components such as radiators and air intakes where there would be minimum airframe drag. And then installed one of the most powerful and reliable engines in the U.S. inventory — the thirteen hundred horse power Allison engine.

As with many new aircraft, early versions of the Mustang left much to be desired. The aerodynamics and airframe were very good, but the twelve cylinder liquid-cooled engine did poorly at high altitudes since it lacked turbo supercharging. Unfortunately, high altitudes were exactly where German bombers and fighter escorts liked to fly. The newly minted fighter did fine in low level ground attack and reconnaissance missions — but that's not what it was designed for.

Then the British had an idea. Why not use their excellent high altitude performing Rolls-Royce Merlin engine from their equally excellent Spitfire in the Mustang? This unlikely marriage of American aerodynamics and British muscle coalesced to produce one of the best fighter aircraft of WWII.

Air Force

America took notice of the leap in performance with the new engine and quickly ramped up production for its own inventory. With the Mustang, the allies finally had a fighter plane that could escort bombers deep into Germany and still fight on equal terms with Nazi aircraft.

Through design synergy and broad thinking, the aircraft that started as an underperforming afterthought helped end the bloodiest war of the 20th century.

I'm Fitz Walker on behalf of the University of Houston, interested in the way inventive minds work.

(Theme music)

Rolls-Royce Merlin Engine:

Bucholtz, Chris. Mustang Aces of the 357th Fighter Group. UK: Osprey Publishing, 2010. Print.

The photograph is in the Creative Commons through Wikipedia. The other two images are from the Air Force gallery.

This episode was first aired on February 3, 2012