By Marcie Holmes, PhD
MATCHING HUMANS TO MACHINES
“There’s no such thing as a natural-born pilot.” - Chuck Yeager
Good airplane pilots are made, not born. The United States’ armed services have been making good pilots ever since 1909, when the Army Signal Corps opened the first military training base for pilots in College Park, Maryland. As aircraft have become faster, more maneuverable, and more powerful, so the military’s techniques for selecting and training pilots have become more rigorous and scientific. These techniques - as methods of matching human skills to the operations of machines - helped to make the airplane into the premier example of human-machine interaction, and the ultimate symbol of American technological prowess, in the years before the atomic bomb and the digital computer. But while these procedures for selection and training were developed throughout the military and even in commercial aviation, the story of how and why these methods were created is closely linked to the history of the U.S. Air Force. After decades in the shadow of the Army and Navy, the Air Force emerged as an elite military service during World War II, becoming an independent service branch in 1947. For the Air Force, “matching men to machines” has proved essential to avoiding accidents, achieving its missions, and shaping its distinctive military culture.
THE INVENTION OF THE AIR CRAFT PILOT
In 1903, the Wright brothers, Wilbur and Orville, became the first Americans to pilot an aircraft for a controlled, sustained, and engine-powered flight. They spent the next decade improving their airplane designs, fighting to protect their patents from rivals, and trying to sell their inventions to governments and businesses around the world. When the U.S. Army Signal Corps agreed to purchase their airplanes, the Wright brothers offered to teach military men how to fly. In 1909, the Army Signal Corps leased an airstrip in College Park, Maryland as a location for Wilbur Wright to train the first two Army lieutenants to become pilots, Frederic Humphreys and Frank Lahm. The Wright brothers went on to train over 100 pilots at their aviation school in Dayton, Ohio, including the man who would later become the head of the U.S. Army’s Air Forces in the Second World War, Henry “Hap” Arnold.
Throughout these early years of military aviation, and indeed for years after, the armed services weathered tragedy as many pilots crashed their airplanes, often with lethal consequences. These accidents could be caused by human error, mechanical faults, weather conditions, or an unfortunate combination of these factors. One strategy for reducing accidents, which the Army Signal Corps quickly adopted, was to select officers for pilot training who had already distinguished themselves by their mental and physical abilities. Volunteers for pilot training were vetted for their courage, athleticism, intellect and ability to estimate distances by sight - usually on the basis of their superiors’ personal judgements. The heroic characteristics of early pilots only added to the sense of tragedy when a spate of accidents in 1912-1913 killed seven promising Army pilots. The mounting casualty rate inspired the Signal Corps to take up another strategy: to encourage aircraft designers to make new planes that were easier to control and safer to fly.
WORLD WAR I: Pilots Prove their Heroism Prior to World War I, the U.S. Army Signal Corps had backed the Wright Brothers’ new experimental technology largely because it believed that aviation would be a tool of reconnaissance. Army officers, who were used to thinking about war as a conflict on the ground, saw airplanes as a way to fly over enemy forces, observe their formations and resources, and then report this information to Army commanders (a similar perspective held sway in the Navy). However in World War I, the Signal Corps’ pilots showed that they could fight battles in the air by mounting guns on their aircraft and engaging in aerial “dogfights” with enemy aircraft. Airplanes were also used to drop small bombs on enemy ground forces and ships, though this was a strategy used more by the British, French and Germans than by American flyers. The Army’s growing recognition that aviation could be very useful in warfare led to more pilots being trained during World War I. In April 1917, the Aviation Section of the Signal Corps had less than 100 pilots; by the end of the war, it had almost 1400. During the war, the Army sent its would-be pilots to university campuses around the country for the first phase of their training. There cadets learned military discipline, took classes on the principles of flight, and were taught skills necessary for flying, such as how to navigate by “dead reckoning” and how to operate a radio for communication. Those who graduated from this “ground training” would be sent to flight schools, either in the U.S. or in Europe, to learn how to fly aircraft.
However, only about 25% of the volunteers for the Aviation Section made it to flight school. During World War I, the Army instituted strict controls on who entered ground training and who graduated on to flight school. This was because accidents in training simply cost too
much in money, time, and soldiers’ lives. Thus, the Army officers who oversaw ground training were keen to “wash out” men who lacked good judgement or did not behave in the disciplined manner of a pilot. One officer later explained, “We were constantly enjoined to remember that the flying officer was not to be an ‘aerial chauffeur,’ but a ‘twentieth century cavalry officer mounted on Pegasus.” In 1917 medical examinations were established as a way to screen recruits for their physical fitness. These examinations included tests of vision, hearing and motor control, and general health. They also involved a test of “nervous stability” that gauged a person’s reaction to the sound of a gun being fired, and a test of equilibrium that involved being strapped into a chair that spun in three dimensions - what is known as a Barany chair, as it named after its inventor, the Hungarian physiologist Róbert Bárány.
These physiological examinations fascinated other scientists, who saw in them the possibility of scientifically matching human skill to the needs of machine operation. In the summer of 1917, two experimental psychologists undertook a study of whether these examinations were actually successful in predicting who became successful pilots. By the end of 1918, their research was supported by the National Research Council (a part of the National Academy of Sciences) and they had the assistance of several eminent psychologists. More importantly, they had identified the techniques that seemed to be most predictive of piloting skill - among them, the tests of nervous stability and equilibrium. However, before their experiments could achieve conclusive results, the war ended and the funding for their research ran out. The question of which tests worked best for selecting pilots would go unanswered until the Second World War. 
THE INTERWAR YEARS
World War I had revealed the utility of airplanes in war, but high ranking military commanders in the Army and Navy still saw aviation as secondary to their forces on the ground and at sea. Within the Army’s newly constituted Air Service, leaders like Hap Arnold and General William “Billy” Mitchell bridled at the short-sightedness of Army commanders
who preferred to give status and
resources to ground troops rather than to air men. General Mitchell would be court-martialed in 1925 for publicly criticizing Army and Navy leaders, but his predictions would prove true that air power was necessary for strategic warfare and defense.
The interwar years saw new innovations in cockpit instrumentation, enabling pilots to more easily keep track of their plane’s altitude, attitude, speed and bearing. A skilled pilot could use these new instruments to fly “blind”, that is, without being to see outside his cockpit, and still safely reach his destination. This was a remarkable development, as previously it was only safe to fly when there was maximum visibility: during the day and in clear weather. However, the skills of blind flying - also known as “instrument flying” - were challenging to learn, and were dangerous for a novice to practice in the air. The solution, it was quickly realized, was to familiarize pilots with the new cockpit instruments while they were still on the ground.
In 1929, Edwin Albert Link Jr., an amateur pilot, invented the “Link trainer,” using a small airplane fuselage and motors and bellows from Link’s father’s piano and organ company in Binghamton, NY. He initially designed his machine to teach students basic control maneuvers, but he soon added knobs and dials to simulate the new instruments. The Link Trainer was used widely throughout the 1930s and into the 1950s - even by the Japanese, Germans and Russians - to teach instrument flying. As the first mechanical flight simulator, it is
an example of a machine designed specifically for new pilots to prepare them to operate more sophisticated machines in dangerous environments.
The Army’s emphasis on medical examinations during the First World War had led to the creation of a new profession within the Army, the “flight surgeon.” Flight surgeons were specially trained doctors who could assess potential pilots for mental and physiological defects that would affect their flying, and who saw to the medical needs of aviators. After the war, the Army’s General Theodore C. Lyster established an institution to train flight surgeons, the School for Aviation Medicine, at Mineola, Long Island (the school later moved to Brooks Field near San Antonio, Texas and then to Randolph Field). The School of Aviation Medicine was also initially a site for medical research, and under Lyster its flight surgeons performed experiments on the effects of high altitude using a low-pressure chamber. By the time the school had moved to Texas, it had ceased its research and focused only on training. The low-pressure chamber was used to introduce cadets to the performance-diminishing effects of being at high altitude without an breathing apparatus and oxygen tank.
Medical research for Army aviation was not revived until 1935, when Capt. Harry G. Armstrong became the director of a new Aeromedical Research Laboratory at Wright Field in Dayton, Ohio. Armstrong and his staff conducted experiments on the effects of cold, lack of oxygen, acceleration, and cabin pressurization on the human body, and also developed new equipment to help aviators perform better at high altitudes. Under Armstrong’s direction, by the end of World War II, both the Aeromedical Research Lab and the School of Aviation Medicine would be world-leading scientific institutions for the study of human physiology and psychology in flight. In the wake of World War I, military strategists like Billy Mitchell and Giulio Douhet predicted that in the future airplanes should be used for the strategic bombing of military targets. Indeed, after the bitter and prolonged trench warfare of World War I, the idea of strategically bombing supply lines, weapons factories and military headquarters seemed like an almost “humane” way to end a war without extensive casualties. This seemingly ideal form of war was mainly theoretical until the Spanish Civil War in the 1930s, when Hitler’s Luftwaffe and the Italian Royal Air Force, working with Spanish Nationalist forces, bombed Spanish cities, killing thousands of civilians in their homes. People around the world, and many Americans, were shocked at the barbarity of aerial bombardment.
But air strategists argued that strategic bombing would be civilized, and still be effective, if bomber planes did not target civilians. The invention of sophisticated “bombsights” - precision calculators for timing the release of bombs - would enable American air forces to surgically strike at enemy forces from the air, without attacking civilian areas. Each bombsight was essentially a telescope combined with a mechanical computer that could calculate the precise moment to drop bombs on a target given the
plane's altitude, azimuth, ground speed, and the cross winds that would affect the course of the bomb in the air. This emerging doctrine for air power, known as “High Altitude Daylight Precision Bombing,” would become the stated mission of the Army’s Air Forces during World War II.
WORLD WAR II: Selecting aviators becomes scientific
As conflict brewed in Europe and Asia in the late 1930s, the American military services debated what their strategy should be when war broke out. By then, the Army’s aviators had gained some autonomy from the Army ground forces, but they were still dependent on Army leadership for funding and material. Yet the idea that aviation could be an independent force within the American military was taking hold. In the summer of 1941 the War Department officially approved the strategic doctrine of precision bombing, and a plan to expand the Army’s air arm to include 30,000 new pilots.  Reflecting this new status, the Army’s aviation section was renamed the Army Air Forces (AAF).
As the AAF first began ramping up their preparations for war in the summer of 1941, flight surgeons recognized that their procedures for examining and selecting aviation cadets would have to be updated significantly if the Army was going to reach its quota of 30,000 new pilots. Under their existing selection procedures, they would have had to screen an estimated 300,000 men, because nearly 80% of recruits would be eliminated for physical reasons and a further 50% would be “washed out” during training. The head of the AAF’s Medical Division, General David N.W. Grant, believed that written mental tests should be administered to all recruits. This would identify those who lacked the ability to graduate from ground school, and thus reduce the number of physical examinations that surgeons needed to perform.
To design the tests, Grant commissioned a relatively unknown educational psychologist named John C. Flanagan. Flanagan recruited a small staff of talented psychologists to help him create tests for aptitude in aviation. In a way, Flanagan’s team picked up where World War I psychologists had left off, as the tests for pilots had not dramatically changed since World War I. But unlike in WWI, Flanagan and his staff were in a position to accumulate data on each test, and on each test taker. They would use this data to assess which tests were best at predicting who graduated from flight training. With growing support from General Grant and the Medical Division for their efforts, Flanagan and his staff called themselves the AAF Aviation Psychology Program.
The AAF Aviation Psychology Program was just underway when Pearl Harbor was attacked on December 7, 1941. The need to select, train and produce top-notch pilots had never been greater. Working quickly, Flanagan's staff assembled a general aptitude test of 150 multiple choice questions, each framed to emphasize terms and concepts that AAF cadets would encounter in their ground courses. The test, which came to be known as the Aviation Cadet Qualifying Examination, covered general vocabulary, reading comprehension, mathematics, and mechanical reasoning. By January 15, 1942 it was in use in AAF recruitment centers to determine who would become a cadet (a trainee officer), a necessary step to becoming a pilot. The Qualifying Examination was later found to be highly effective in reducing the number of wash-outs from pre-flight training. It cut in half the number of applicants requiring further in-depth evaluation by flight surgeons.
However, in World War II the Army Air Forces did not just need pilots; it needed thousands of bombardiers, navigators, gunners, radio operators, and radar operators—as well as mechanics, technicians and other ground crew. The AAF’s strategy of High Altitude Daylight Precision Bombing required that for every three pilots trained, the AAF needed to train one bombardier and one navigator. But compared to pilots, these positions were less glamorous. The AAF had difficulty recruiting suitable men for these less-respected position, especially as the AAF had to compete with the Navy and Army Ground Forces for top talent. Even the roles of bombardier
and navigator were a tough sell because while they were officer positions within the AAF, it was generally believed that bombardiers and navigators were wannabe pilots who had washed out from training.
In 1942 the AAF’s top commander, General Hap Arnold, called for a publicity campaign to promote the importance of bombardiers and navigators. He hoped this campaign would make clear these positions’ equal rank with pilots and their necessity for strategic bombing. The campaign produced films, stage plays, radio shows, novels, and many magazine and newspaper articles, all touting the teamwork of skilled specialists in the work of precision bombing. For example, a cover article in LIFE magazine declared in 1942 that the pilot, bombardier and navigator, along with gunners, radio operators and ground crew, formed a “task force” that would rain down bombs on strategic Axis targets. Gen. Arnold personally asked the famous American author, John Steinbeck, to write a short novel about the bomber crew as a team of specialists. Steinbeck toured AAF training bases around the country to observe the different kinds of air crew personnel training for their specified tasks. The resulting book, Bombs Away! The Story of a Bomber Team, was published in 1942.  The AAF also produced short films that were shown in cinemas to motivate young men to sign up for the AAF. In the film, “His New World,” produced by the Office of War Information in 1944, Spencer Tracy narrates a story of three boys entering the AAF, taking mental and physical tests, and then being trained in different specialist tasks.
Some of these publicity pieces featured the work of the AAF’s Aviation Psychology Program as a scientific means for sorting pilots, bombardiers and navigators. Indeed after Flanagan and his staff had created the Qualifying Examination for selecting men for officer training, they turned to constructing a “battery” of several written and
psychomotor tests that could assess the various skills and aptitudes of incoming cadets. Beginning in 1942, this battery was used by AAF training personnel to classify incoming cadets according to who had the most promise as pilots, bombardiers or navigators. Later versions of the classification battery also differentiated radar operators, gunners, and fighter versus bomber pilots. To create this scientific means of aircrew classification, the Aviation Psychology Program designed six hours of written tests and two hours of tests of psychomotor skill. For the written tests, the AAF’s psychologists tried out different combinations of standard tests of scholastic aptitude as well as tests involving reading tables, graphs, dials, and maps; tests for perceiving patterns and identifying shapes; and tests for perceiving spatial orientation. Psychologists considered personality and temperament to be important indicators of aircrew abilities, and so experimented with attitude inventories, projective methods, and tests of masculinity, fear, and carefulness. However, these tests of personality and temperament did not prove effective in identifying who was best suited to which aircrew position, and so were not included in the official battery. For tests of psychomotor skill, the Aviation Psychology Program utilized apparatus that had been developed by the School of Aviation Medicine in recent years. The “Two-Hand Coordination Test” and the “Rotary Pursuit Test” asked cadets to use their right and left hands simultaneously in independent tasks. The Complex Coordinator asked cadets to operate a control stick with their arms and a rudder with their feet in response to changing lights on a display, as if they were seated in a rudimentary cockpit. These apparatus-based tests evoked the same sort of popular fascination as the First World War’s tests of stability and equilibrium. Interestingly, the Aviation Psychology Program experimented with including different forms of the nervous stability test and the equilibrium test, but found that these long-respected devices were not particularly good at differentiating between pilots, bombardiers and navigators.
By the end of the war, AAF’s Aviation Psychology Program’s psychological tests had selected and sorted hundreds of thousands of men for air force training. The AAF’s psychologists had also begun to advise the Air Training Command on which training exercises were most effective in determining who was developing the needed skills for combat. Surprisingly, psychologists found that the best test of an individual bombardier’s ability was not a mock bombing run in an actual airplane, because flights were often affected by weather, technical idiosyncrasies, pilot error and other
variations beyond the bombardier’s control. Rather, the most powerful indication of a bombardier’s individual skill in dropping bombs on target was his performance in the A-2 trainer, a mechanical simulator for practicing how to use a bombsight. Beginning in World War II, psychologists within the Air Force and in other military branches took increasing interest in the design of such “trainers,” and lent their expertise to engineers who needed to construct machines that could reliably and efficiently simulate complex tasks like gunnery, radar surveillance, and piloting.
World War II had accomplished what World War I could not: it showed beyond doubt that an independent air force was essential to U.S. military power, and it allowed techniques for selecting and training air force personnel to be established on a scientific foundation. In the midst of victory celebrations, the AAF did not forget the contributions that psychologists made to the training of air force personnel. In 1946, John Flanagan received the Legion of Merit for his direction of the AAF Aviation Psychology Program. The office of the commanding general of the AAF publicly praised the program, asserting that “The Aviation Psychology Program paid off in time, lives, and money saved, and through its selection of the raw material has aided in the establishment of an effective combat air force. This has been done at a total cost of less than $5 per candidate tested.”. However, the best testament to the AAF’s Aviation Psychology Program is the Air Force’s continuous support for research in “aviation psychology” after the war. The program itself was disbanded but, after the the National Security Act of 1947 gave the Air Force full independence from the Army, the Air Force created a series of research centers and laboratories for the psychological study of selection, classification, and training. Aviation psychologists' efforts to match humans to machines were expanded during the Cold War as tests and training programs were created for astronauts, air traffic controllers and other skilled positions. Even now, in our age of digital automation and drone warfare, the Air Force uses rigorous psychological tests to evaluate its officer and enlisted personnel, and to assign them to training. Though the development of scientific techniques for selecting and classifying personnel is only one factor in the emergence of the modern US Air Force, these two histories have been closely, even inextricably, intertwined. And arguably, they will continue to be for a long time to come.
Do Your Own Research
 Tom D. Crouch, The Bishop's Boys: A Life of Wilbur and Orville Wright (New York: W. W. Norton & Co, 2003), 435-439; Rebecca Hancock Cameron, Training to Fly: Military Flight Training, 1907-1945 (Washington, DC: Air Force History and Museums Program, 1999), 21-26.
 Cameron, 54.
 J.M. Koonce, J.M. “A Brief History of Aviation Psychology” Human Factors: The Journal of the Human Factors and Ergonomics Society, 26/5 (1984): 499–508, 500; Thomas Manning, History of Air Education and Training Command, 1942-2002 (Randolph Air Force Base: Office of History and Research, Headquarters, Air Education and Training Command), 1.
 Cameron, 112-120.
 Koonce, 500.
 V. A.C. Henmon, “Air Service Tests of Aptitude for Flying,” Journal of Applied Psychology 3, no. 2 (1919): 103–9, 103.
 Henmon; Robert M. Yerkes, "Report of the psychology committee of the National Research Council" Psychological Review 26/2 (1919): 83-149, 94-99.
 Fact Sheet: Brig. Gen. William “Billy” Mitchell, Cameron, 264-270; Erik M. Conway, Blind Landings: Low-Visibility Operations in American Aviation, 1918–1958 (Baltimore: Johns Hopkins University Press 2006).
 Chihyung Jeon, "The Virtual Flier: The Link Trainer, Flight Simulation, and Pilot Identity," Technology and Culture, 56/1 (2015): 28-53.
 Maura Phillips Mackowski, Testing the Limits: Aviation Medicine and the Origins of Manned Space Flight (College Station: Texas A&M University Press, 2006), Ch 1.
 See, for example, the English translation of Douhet's famous work on air strategy, Il dominio dell'aria (1921): Giulio Douhet, The Command of the Air, tr. Dino Ferrari, (Coward-McCann 1942, reprinted by the Air Force History and Museums Program in 1998).
 Michael S. Sherry, The Rise of American Air Power: The Creation of Armageddon (New Haven: Yale University Press, 1987), chap 3.
 Sherry; Stephen Lee McFarland, America’s Pursuit of Precision Bombing, 1910-1945 (Washington: Smithsonian Institution Press, 1995).
 The AAF's strategy for strategic bombing was outlined in “Air War Plans Division-1” also known as AWPD/1.
 Marcia E. Holmes, “The Psychologist and the Bombardier: The Army Air Forces' Aircrew Classification Program in WWII,” Endeavour 38/1 (March 2014): 43-54.
 Frederick B. Davis, ed., The AAF Qualifying Examination, Army Air Forces Aviation Psychology Program Research Reports 6 (Washington DC: US Government Printing Office, 1947).
 Ibid., 231.
 Cameron, 428.
 This book was recently reprinted as John Steinbeck, Bombs Away: The Story of a Bomber Team, 2nd ed. (New York: Penguin Books, 2009).
 Arthur W. Melton, ed., Apparatus Tests, Army Air Forces Aviation Psychology Program Research Reports, Vol. 4 (Washington, D.C: US Government Printing Office, 1947).
 Kemp, Edward H., and A. Pemberton Johnson, eds. Psychological Research on Bombardier Training, Vol 9. Army Air Forces Aviation Psychology Program Research Reports. (Washington, D.C: U.S. Govt. Print. Off, 1947).