Testing the Hypothesis
In 1886, Samuel Pierpont Langley attended a meeting of the American Association for the Advancement of Science in Buffalo, N.Y during which the research of Israel Lancaster, an amateur aeronautics experimenter, was presented. While Lancaster’s work disappointed those in attendance, Langley left intrigued and determined to conduct his own experiments. He began his work in secret, in part because the pursuit of flight was considered quackery by many in the scientific community. With limited research to guide him, Langley studied the work of Alphonse Penaud, a French aviation pioneer, who developed the first aerodynamically stable rubber band-powered flying model. Langley set out to create reproducible experiments on models of varying configuration from which he could evaluate the properties of rigid plane surfaces in flight.
In 1887, Langley constructed a “whirling table,” a belt driven contraption with two 30’ long spinning radial arms, eight feet off the ground, on the grounds of the Allegheny Observatory, which enabled him to study lift, drag, and stability of 30-40 different model prototypes. Initially driven by a 1-1/2 hp gas engine, the machine was upgraded in 1888 with a steam engine which could rotate the arms up to 150 revolutions per minute. Langley invented data recording instruments and connected them to the whirling table to record data from each experiment. The Resultant Pressure Recorder graphed pressure applied to a plane and the Dynamometer-Chronograph measured speed and resistance to forward motion.
“Rubber-Motor Driven Model Aerodromes Nos. 11, 13, 14, 15, 26, 30, 31,” Smithsonian Contributions to Knowledge Vol 27, No. 3 Pl. 1, Langley, S. P., and Charles M. Manly. Langley Memoir on Mechanical Flight. Published by the Smithsonian Institution, 1911.
By incrementally adjusting wing placement and attitude, Langley derived mathematical equations for the power (thrust) and properties of rigid plane surfaces needed to achieve and sustain flight. Over the next four years, Langley’s models grew larger, up to 4-1/2’ long with 4’ wingspans, and more complex with design characteristics that would be incorporated into aircraft for decades.
In August 1891, Langley concluded and published the results of his work in a report of the Smithsonian Contribution to Knowledge entitled, “Experiments in Aerodynamics,” the first substantial American scientific contribution to aerodynamics. In his introduction, Langley stated, “I do not undertake to explain any art of mechanical flight, but to demonstrate experimentally certain propositions in aerodynamics which prove that such flight under proper direction is practicable.”
“Rubber-Motor Driven Model Aerodrome No. 26,” Smithsonian Contributions to Knowledge Vol 27, No. 3 Pl. 4, Langley, S. P., and Charles M. Manly. Langley Memoir on Mechanical Flight. Published by the Smithsonian Institution, 1911.
Langley closed “Experiments in Aerodynamics” with the following conclusions:
“This being understood, I may state that these researches have led to the result that mechanical sustentation of heavy bodies in the air, combined with very great speeds, is not only possible, but within the reach of mechanical means we actually possess, and that while these researches are, as I have said, not meant to demonstrate the art of guiding such heavy bodies in flight, they do show that we now have the power to sustain and propel them.”
The most important general inference from these experiments, as a whole, is that, so far as the mere power to sustain heavy bodies in the air by mechanical flight goes, such mechanical flight is possible with engines we now possess, since effective steam - engines have lately been built weighing less than 10 pounds to one horse - power, and the experiments show that if we multiply the small planes which have been actually use, or assume a larger plane to have approximately the properties of similar small ones, one horse - power rightly applied, can sustain over 200 pounds in the air at a horizontal velocity of over 20 meters per second (about 45 miles an hour), and still more at still higher velocities.
While calling attention to these important and as yet little known truths, I desire to add as a final caution, that I have not asserted that planes such as are here employed in experiment, or even that planes of any kind, are the best forms to use in mechanical flight, and that I have also not asserted, without qualification, that mechanical flight is practically possible, since this involves questions as to the method of constructing the mechanism, of securing its safe ascent and descent, and also of securing the indispensable condition for the economic use of the power I have shown to be at our disposal — the condition, I mean, of our ability to guide it in the desired horizontal direction during transport, -questions which, in my opinion, are only to be answered by further experiment, and which belong to the inchoate art or science of aerodromics, on which I do not enter. I wish, however, to put on record my belief that the time has come for these questions to engage the serious attention, not only of engineers, but of all interested in the possibly near practical solution of a problem, one of the most important in its consequences, of any which has ever presented itself in mechanics; for this solution, it is here shown, cannot longer be considered beyond our capacity to reach.”
- Samuel Pierpont Langley, Experiments in Aerodynamics, August 1891
Samuel Pierpont Langley Cabinet Photo, August 22, 1887, Smithsonian Institution Archives, Record Unit 95, Box 15, Folder: 1
Despite his pledge to leave further advancement of his work to others, Langley’s confidence in his research launched a relentless pursuit of mechanical flight over the next five years and the invention of his “air-runners.”