Wednesday, December 13

Sir George Cayley and the Foundation of Aerodynamics

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Imitation, it has often been said, is the sincerest form of flattery.  But, in the case of aviation, it was also a necessity, because, before manned flight could be achieved, dreamers and experimenters alike relied upon the only flying creatures then in existence—the birds—for inspiration.  Although success would ultimately hinge upon the understanding of the three axes of flight, several would-be conquerors paved the path toward it.  One of them was Sir George Cayley.

Hailing from England, he was intensely interested in mechanics and took copious notes about everything, particularly nature, which, he believed, held the secrets to flight, and he devoted two periods of his life to this quest.

During the first, from 1799 to 1809, he postulated that, contrary to current consensus, that he did not believe that birds flew solely as a result of their wing-flapping, but instead were able to soar when they extended those wings in a single plane and flew in a straight line.  Therein lay the deception that deflected the truth from all others.

Although the wing’s straight geometry could not be refuted when viewed from a distance, a closer examination revealed that they were actually inclined—albeit it at almost imperceptible angles—to the forward air flow, and he dubbed this phenomenon “angle of incidence”—or the angle between the wing’s chordline and the relative wind.

The revelation enabled him to calculate the amount of force and resistance this angle provided, along with the amount of power the bird needed to remain airborne, and from this he stumbled upon what he believed were the three forces of flight: lift, resistance (drag), and power (thrust).  Of course, he failed to identify the fourth—weight—created by the very gravity an airplane needed to overcome.

During his second aviation focus, from 1843 to 1853, he continued to test his theories of lift with model gliders, which sported either propulsive flappers or both fixed wing surfaces and the flappers themselves to generate propulsion and lift, until he was ready to build a man-carrying machine.

The pinnacle of his aeronautical path was surmounted with two full-size designs.  The first, a triplane with short-span wings, 338 square feet of surface area, and a 130-pound empty weight, was launched from a hill in 1849.  The second, also believed to have been a triplane, became the first human-carrying glider when Cayley’s coachman, John Appleby, served as its pilot/passenger, as he watched his aerial vehicle being pulled toward the downward slope of the hill at the Brompton Hall estate where he worked.  Cascading down it, it disconnected from the ground and then bounced to an abrupt stop.

Shaken and ignorant of the role he had just played in aeronautical development, he realized the dangerously expanded realm of his job description and promptly resigned.  “I was hired to drive, not fly,” he said.

Although Cayley, now an octogenarian, lacked a suitable propulsion source and died three years after this “successful flight,” he nevertheless laid the first stone in what would later become the science of aerodynamics and defined the modern airplane configuration.

Cayley’s angles of incidence are incorporated in the wings of all of Old Rhinebeck’s aircraft, but are particularly pronounced on those of the Bleriot XI, the Fokker Dr.1 and D.VII, the Thomas Pusher (in the Pioneer Hangar), and the New Standard D-25, which has carried countless thousands of “aerodrome passengers” over the Hudson Valley.

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