But the real unsung hero is someone else. Frederick A. Lindemann was a bespectacled theoretician smitten with flying, but he was initially rejected by the Royal Flying Corps because of poor vision. He succeeded in getting a pilot's license by using his prodigious memory to memorize the eye chart (like Donald Sutherland did in the film Space Cowboys). He was soon appointed director of its Experimental Physics Station at Farnborough. His poor eyesight was actually only one handicap. Another, which he regarded as far worse during the war with Germany, was his surname and the fact that he actually had been born in Germany while his mother was vacationing in Baden-Baden. He later used his family's influence to join the scientific staff at the Royal Aircraft Factory.
It wasn't all peerage and puffery, however. Lindemann initiated a study of instrument indications and pilot actions that appeared to cause spin entries during turns, and with little flying skill of his own, he successfully determined the causes of stall/spin occurrences as well as the control movements needed to counteract them. His contributions to aviation actually occurred during a relatively brief period in his life. After the war, he was a professor of philosophy at Oxford University and the director of the Clarendon laboratory. He made contributions in thermodynamics and quantum theory, was a close friend of and scientific advisor to Winston Churchill, was Great Britain's leading scientific advisor during World War II, and created his country's Atomic Energy Authority.
In 1956, he became the Viscount of Cherwell. He was also formal to nearly a comical degree, never emerging from an airplane without a full coat, umbrella, and bowler hat.
The demands of war necessitated rapid advances in the study of flight, taking it from an art to a science, and Lindemann became one of the key individuals in transforming the military's languid interest in airplanes to the realization of aviation's strategic value above the battlefield. His conclusion regarding spins was the correct one; namely that a pilot's instinctive responses were the wrong responses. One must, he reasoned, apply and maintain full opposite rudder while the nose was pointed at the ground. Furthermore, one should not pull back until the spin stopped.
Ah, but how to test this? Here is where Lindemann entered the realm of greatness, testing his theory with himself as the test pilot. Observers from the Farnborough Aerodrome saw him take a spindly B.E.2 biplane up to its service ceiling (depending on the model, this was between 10,000 and 14,000 feet), deliberately enter a fully-established spin, and then put his theory to the ultimate test. Not only did he come out of it, but he then climbed back up and recovered from a spin in the opposite direction. There are differing accounts as to when this occurred; according to the book The Prof in Two Worlds, by the second Earl of Birkenhead, it was in the summer of 1916 or 1917.
In His Own Words:
Anyone watching a spinning plane could see that the rate of turn did not increase on the way down. I concluded therefore that the lift on both wings must be equal; and this could only be true - since the outer wing is beating against the air whereas the inner is not - if its effective angle of incidence was on the high side of the angle of maximum lift, whereas for the inner wing it was the other way round. This being so, if the speed were increased the aeroplane would no longer spin...therefore the pilots were taught to push the stick forward - the very opposite of the instinctive reaction of pulling it back in order to get the nose up - and to straighten out the rudder and then pull out of the dive in the ordinary way.
The only merit I can claim in carrying out these experiments is that (unlike the professional pilot, who had usually not got a very good head for figures) I was able to remember the readings of the airspeed indicator, the bubble, the angle of incidence on the two wings (measured by tapes on the struts), the height at the beginning and ending of the spin, the time taken and the number of turns, and to write them down in my note-book when I had straightened out the plane again.
For awhile, the British kept this military secret and used it much to their advantage. Whenever a British pilot was outnumbered and needed to escape, from the perspective of his German opponents he would seemingly commit suicide and spin away and down, only to recover close to the ground and speed safely away. Pilots talk, however, and soon the secret was out.
If Lindemann hadn't documented his discovery, someone else would have figured it out sooner or later. While knowing how to get out of a spin is of great value, this can be academic because most spin accidents (which have somewhere around an 80-percent fatality rate) occur at an altitude too low for recovery in all but about 5 percent of the cases. Perhaps this is what the Civil Aeronautics Administration had in mind when it deleted spins from the list of required maneuvers in 1949. Since an airplane cannot spin unless it is stalled, emphasis was shifted from spin recovery to stall recognition and recovery. Today, only CFI applicants are required to have actual exposure to spin entries and recoveries - but private pilots, and even student pilots, can seek spin training if they want.
As long as pilots fly, there will probably always be two schools of thought regarding spins. As Benjamin Disraeli reportedly said, there are three kinds of lies: lies, damned lies, and statistics. One study showed that many stall-spin accidents occurred in conjunction with aerobatics and buzzing (though half were associated with takeoff and landing). The journal Aviation Safety published a study in 1983 which showed that the percentages of stall/spin accidents actually increased as flight time increased. And an analysis of stall/spin accidents involving instructional flying showed that in more than half the mishaps, a CFI was aboard. What really tells the tale, however, are the general accident data during the years before the CAA eliminated spin training, and then afterwards: From 1945 to 1948, almost half of all fatal accidents were stall/spin-related. Two decades later, the comparable figure was about 22 percent. Since then, stall/spin accidents have stabilized at about 10 percent of all accidents, but 25 percent of fatal accidents. (And slightly over half are still associated with the takeoff and landing phases of flight.) So yes, the shift to stall and spin avoidance is supported by the numbers.
Just what is a spin? A spin is an aggravated stall resulting in autorotation around the yaw, or vertical, axis. (Autorotation means the downward helical path wherein both wings are stalled, one more than the other.) Two factors working against us are that near critical angles of attack, roll damping vanishes, so not only do ailerons lose effectiveness, but they begin to work adversely. The inner wing is at a greater angle of attack than the outer wing, and it is the greater drag on the inner wing that causes rotation about the vertical axis. The motion involves elements of roll, pitch, and yaw, where the airplane is in somewhat of a sideslip.
Although the view of the ground through your windshield can be initially disconcerting, a spin is strictly a one-G maneuver. The typical recovery technique is to determine the direction of rotation, then neutralize the ailerons and close the throttle. Next, apply full opposite rudder, and briskly move the yoke or stick forward (though in some airplanes, just neutralized), holding this until rotation stops. Then pull out of the dive. The opposite rudder produces a yaw moment that counters the direction of rotation, and the forward yoke movement gives a nose-down moment that reduces the angle of attack.
What can we do to improve the safety picture? One would be to practice slow flight and stalls on a regular basis. Another would be to pay more attention to airspeed and coordinated flight, especially during takeoff and landing. It would be beneficial if the FAA required flight instructor applicants to undertake more than two logged spins. Finally, we should rise above minimum acceptable training standards and seek out spin training from qualified instructors as part of our continuing education.
Jeff Pardo is an aviation writer in Maryland with a commercial pilot certificate for airplanes, and instrument, helicopter, and glider ratings. He has logged about 1,100 hours.