The test pilot who made airplanes safer (by teaching us how to break them better)

In the years following the Wright brothers’ 1903 takeoff, aircraft were designed via what a NASA history calls “an intuitive, daring empirical engineering loosely connected at best with any theory of aerodynamics or structural integrity.” Plane makers had some ideas about how to mimic flight while on the ground, but these were crude approximations with little sense of similarity or workability (that measure of practicality and reproducibility). The assessment of a plane as insufficiently robust was frequently made amid crashing noises and roaring flames. In the 1920s, the life expectancy of a pilot for the U.S. Air Mail Service (among the first practical uses of civilian aviation) was four years, and the service lost 31 of its first 40 pilots to crashes in its first decade. Much of the problem was that human flight was so new, nobody could fully answer the first, fundamental question in the testing litany: What will the product face, and how might it fail?

Happily for pilots and passengers since, the U.S. Army let one Jimmy Doolittle pause his work as a test pilot to help figure it out. Thanks to a cringeworthy script and a hammy portrayal by Alec Baldwin, anyone who saw 2001’s Pearl Harbor may think of Doolittle as a jingoistic flyboy who spouted lines like “Victory belongs to those who believe in it the most and believe in it the longest …. We’re gonna make America believe.” The real Doolittle was, in fact, not just a daring and gifted pilot but an inveterate mischief-maker and premier aeronautical mind who worked to rationalize the airplane into something that could be known, predicted, and judged. Something that could be tested.

Small but fierce, Doolittle was a champion boxer in college, an avid acrobat (he was particularly keen on tumbling), and one of the many people who took to flying in the early years of the 20th century. He started as a teenager building his own gliders from sticks and cloth, promptly crashing each one. In one case, he tied himself to his friend’s car to pick up speed for takeoff, only to end up being dragged down the road. His autobiography, I Could Never Be So Lucky Again (1991), includes an inordinate number of stories that end with him climbing out of a wrecked plane, amazingly unhurt, then being chewed out by a superior officer. In a typical tale, he once saw two soldiers walking down a road on his base and “decided to give them a little scare” by flying a few feet over their heads. He misjudged the distance and clipped one of them with his landing gear. Distracted by the worry that he’d killed an innocent, he crashed into a barbed wire fence. Somehow, everyone was fine.

After serving as a flight instructor during World War I, Doolittle stayed in the army and started working as a test pilot. He racked up accolades as a short- and long-distance racer, becoming the first person to fly cross-country in under 24 hours, then in under 12. When the Curtiss-Wright Aircraft Company hired him to go to South America to sell pilots on its new P-1 Hawk pursuit plane, Doolittle spent his first night in Santiago getting drunk on pisco sours (“a delightful, powerful drink”) and decided to impress his hosts by doing acrobatics on a window ledge. When the sandstone crumbled under him, Doolittle fell two stories and broke both ankles. Undeterred, he rigged a pair of bootstraps that let him work his plane’s rudder, had someone lift him into the cockpit, and successfully demonstrated the Hawk’s prowess.

In 1924, at the suggestion of his friend Eddie Aldrin (father of astronaut Buzz), Doolittle got a two-year dispensation from the army to pursue a master’s degree at the Massachusetts Institute of Technology’s newly formed aeronautical engineering program. For his thesis, Doolittle addressed what he called “one of the mysteries of flight”: how much stress a plane could take without falling apart. Another way to put it is its load factor, that ratio of a plane’s lifting ability to its weight.

At the time, such strength testing happened mostly on the ground and typically involved piling bags of sand on the wings and tail fins until they broke. That was an upgrade over those who threw loose sand onto their aircraft and used rakes to push it into place – and even that was better than folks like aviation pioneer Thomas Sopwith, who didn’t bother to run this kind of stress test on his early planes before trying them out in the air. (He lived to be a 101.) Doolittle thought he had a better way to determine what kind of loads a plane could take. He created his own in-flight regimen and undertook what Air Force historian Richard P. Hallion deemed “the first major examination of structural loadings during maneuvering flight ever undertaken.”

Doolittle rigged a Fokker PW-7 fighter with an accelerometer to track the load factor, measured in g-forces. Then he piled on steadily greater forces by executing loops, barrel rolls, snap rolls, spins, spirals, and 180-degree turns. He flew upside down and pulled out of dives. “What made the whole effort worthwhile was that I found out exactly what the Fokker could withstand because it nearly came apart during a dive at 200 miles per hour,” Doolittle wrote in his autobiography. As the upper wing cracked, the accelerometer read 7.8 g’s, countering Fokker’s claim that its plane would handle a load factor of 8.5. Doolittle secured his degree and turned his thesis into a report that proved to be an aviation milestone.

A 21st-century flight engineer might quibble with the similarity and workability of such testing. Future PW-7 pilots would face all sorts of conditions Doolittle didn’t try out, and Doolittle didn’t attempt to design a process that he or others would repeat. But in his work — pushing a product to the very limit of its strength and carefully measuring its performance — we can spot an ancestor of the modern, onion-peeling test flight program, down to the cracking of the 777’s wings.

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