Technicalities: Let Us Now Praise George Cayley

When some Connecticut boosters recently dusted off the claim that ­Gustave Whitehead, of the township of Fairfield in that great state, was "first in flight," I, and I suspect quite a few others, emitted the sigh of jaded déjà vu. These "who was first" arguments have become pretty tedious. Predictably, the few who were stirred to action by the Whitehead claim trotted out their own candidates: Clément Ader, Richard Pearse, Karl Jatho, Alberto Santos-­Dumont and so on.

That all of the usual suspects cluster around the turn of the 20th century is no accident. The basic principles of flight were already understood. Model airplanes and man-carrying gliders existed. Beginning around 1890, when small, powerful gasoline engines became available, there was such a surge in aeronautical experimentation that success was both inevitable and imminent. Being first was a distinction ­merely of degree.

The Wrights' claim to priority is the best documented, both photographically and in extensive journals, notebooks and correspondence. Some of the others are doubtful for various reasons, including, in the case of Ader, his batlike Éole's lack of provisions for either stability or control. Any practical airplane needs one or the other, preferably both. Ader's late compatriot, ­Alphonse Pénaud, had already demonstrated, with rubber-band-powered flying models, how stability, both longitudinal and lateral, was to be achieved, but Ader, though no fool, foolishly ignored the message.

But it is pointless to speculate about rival attempts. The Wrights built up to their 1903 success incrementally and systematically, and then continued to develop their designs, with unabated energy, after they had demonstrated sustained and controlled flight. I have trouble taking seriously claims that someone else earlier realized "man's age-old dream of flight" and then just shrugged his shoulders and went back to farming or whatever. To drift away from such a project seems to me evidence not of success but, quite clearly, of frustration.

A century's adulation has engendered around the Wright brothers an aura so blinding that we neglect some of the truly great intellects that had earlier pondered the problem of "aerial navigation." The great figure at the head of the chain that led eventually to the Wrights — its links included Francis Wenham, Alphonse Pénaud, Otto Lilienthal and Octave Chanute — was an English baronet, Sir George Cayley (1773-1857). Cayley was both a gifted engineer and a perspicacious physicist. He invented, among other things, the tension-spoke wheel and the caterpillar tractor and described, in passing, what we now know as the gasoline engine. How little Cayley's work has been honored, however, may be judged from the fact that my 1958 Encyclopaedia ­Britannica, joy and solace of my friendless youth and faithful companion of my dotage, contains no entry for him.

On the theoretical side, Cayley was the first to differentiate, in 1799 — the year George Washington died and Napoleon became the ruler of France — what we now call the four forces acting upon an airplane in flight. He properly distinguished lift and drag, which are measured in relation to the moving air, from weight and thrust, which are related to the earth and to the axis of the thruster, respectively. Observing "the perfect ease with which some birds are suspended in long horizontal flights," he concluded that Newton's pessimistic prediction of the relations of lift and drag to angle of attack was incorrect, and that the most favorable ratio would be found at quite small angles of attack. He reasoned that the soaring bird, to maintain height, must compensate for gradual loss of energy by imperceptibly increasing the angle of attack of its wing before being obliged to expend a few wingbeats to restore its speed.

"I conceive the [generation of lift at small angles of attack] may be of a different nature from what takes place at larger angles," he wrote — a fundamental insight at a time when the roles of flow separation and stalling were unknown and the mechanism of lift was assumed to be the same at all angles of attack up to 90 degrees.

On the practical side, Cayley experimented with models on the end of a whirling arm — a primitive type of wind tunnel — and correctly concluded the forces generated by the air were proportional not to velocity, as was widely thought, but to velocity squared. He reported having had man-carrying gliders built and flown. Given his apparent grasp of the fundamentals, there is no reason to disbelieve his claim. It is troubling, however, that one basic principle seems to have eluded Cayley, in spite of its being on display in the anatomy of soaring birds: the importance of aspect ratio to the efficiency of a wing. Cayley's successor Francis Wenham (1824-1908), a great observer of birds, grasped this element clearly.

It's difficult to appreciate, today, when all these insights have become commonplace, how difficult it was to arrive at them at a time when theories of flight ranged from superstition to outright denial, and when to assert, as Cayley did, that "we shall be able to transport ourselves and families, and their goods and chattels, more securely by air than by water," was to invite castigation as a crank or a simpleton.

Cayley must have had some sense of how far he stood above his contemporaries: He took pains to inscribe on a silver disk, the size of a quarter, a correct geometrical diagram of the forces acting upon a wing, and, on the obverse, a picture of a man-­carrying airplane. The general arrangement of his tiny aircraft, including vertical and horizontal stabilizers well behind the wing, is the one we use today.

In creating that little medallion, Cayley, classically educated like all English noblemen of his day, must have recalled the boast of the Roman poet Horace that his work was "a monument more enduring than bronze." The silver disk, now in the Science Museum in London, was likewise a bid — more diffident than the ancient Roman's — for immortality. It is to us as the Pioneer spacecraft's golden plates, engraved with the naked figures of Adam and Eve, will be to the lobsterlike aliens who may someday intercept them beside a distant star.