(23 Jul 1867 - 1 Mar 1948)
Letters to the Editor.
from Nature (1922)
[p.305] [The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended1 for this or any other part of Nature. No notice is taken of anonymous communications]
The Langley Machine and the Hammondsport Trials.
The leading articles in Nature of November 3 and January 26 last appear to have missed the point of my discourse on the Langley Machine and the Hammondsport Trials. My paper was written to expose a fallacy in which officials of the Smithsonian Institution had used their great opportunities for imposing upon the public a false belief that the Langley machine had been flown in 1914.
The leading articles in Nature, instead of making any denial of the charge that vital changes were made in the Langley machine at Hammondsport before any flight was attempted, contend that my “paper tends to give an erroneous impression of the importance of the part played by the Wright Brothers” in the producing of the first man-carrying aeroplane. Nature suggests that it was Langley who did the laborious work of preparing the scientific data upon which the first aeroplane design was based, and that the Wright Brothers merely contributed the system of wing warping—the final step or “keystone”—in the problem of flight. The writer of the articles in Nature refers to Sir Richard Gregory's book “Discovery,” from which he makes two quotations.
I agree with the author of “Discovery” that many great inventions are based upon pure science, and that often the person who receives the credit for an invention is the one who has added some mechanism which turns the scientific knowledge of another to practical use. In the facts in regard to the invention of the aeroplane, however, the author of “Discovery” and the writer of the leading articles in Nature are in error. The real truth of the discovery of flight is that the Wright Brothers first established a scientific basis for aeroplane design; they then invented the mechanical means for putting this scientific knowledge to practical use. The spectacular Nature of the latter has blinded the public to the importance of the former.
[p.306] In 1914, when I was beginning the preparation of my paper on the “Life and Work of Wilbur Wright,” which was read in 1916 as the fourth Wilbur Wright Memorial Lecture, I visited America to collect material for this lecture. During my stay, which extended over several months, I also studied the practical side of aviation and, at the age of forty-seven, made over a hundred flights on the “unstable” Wright machine. While in Dayton I was allowed to examine, with the privilege of copying, much of the personal correspondence and diaries, as well as the records of the early purely scientific work, of the Wright Brothers. I saw the original balances and twenty or thirty (out of the great number) of the original test surfaces with which the Wright Brothers in 1901 made thousands of measurements in a wind tunnel of the lift and drift and the travel of the centre of pressure on plane and curved surfaces. Copies of the tables obtained from these tests were also given to others who were interested in the problem of flight.
These laboratory measurements (Century Magazine, September 1908, pp. 646-647) covered a field many times greater than had been covered by the work of all other experimenters together. But the importance of the measurements lay in their accuracy. These tables did not agree with the measurements made by Langley or by any of the other experimenters. The Wright Brothers, finding that all marine propellers at that time were based upon empirical formulæ, made a study of propellers by analysing the various dynamic reactions. From these studies they evolved a theory. The propellers used on their first power machine were probably the first ever designed from theory and not from experiment. They made extended studies into the principles of equilibrium, and in this field made important scientific discoveries. Their mechanical means for carrying some of these principles into effect were patented, and the resulting litigation attracted so much attention as to cause the scientific work upon which the patents were based to go without notice. It was upon their own tables and other scientific work that the Wright Brothers built their first power machine.
These scientific experiments were made entirely at the expense of the Wright Brothers themselves, and with no thought or expectation of any other reward than the satisfaction of discovering things unknown before and the honour that naturally comes as a result. It was not until they attempted to build a power machine to carry this scientific knowledge into practical use, an expense too great for their small means, that they took out patents.
My address on the “Langley Machine and the Hammondsport Trials” was not a criticism of Langley nor of his scientific work. This was not a point at issue in my paper. But since the writer of the articles in Nature now brings this into the discussion, I feel that some of his statements should not be allowed to pass uncorrected.
Nature is in error in attributing the discovery to Langley of the inherent stability effect of the dihedral angle of the wings adopted by Langley in his models. This method of maintaining lateral stability in calm air was published by Sir George Cayley a hundred years ago, and was used by Penaud in his flying models in 1870 and 1871. It has never yet been solely relied on for lateral balance in actual human flight, having been always supplemented by aileron control.
The writer in Nature says: “So far back as July 23, 1891, a paper on his (Langley's) experimental researches is to be found in Nature, showing that the flight of a man-carrying aeroplane was possible, and enunciating the fundamental principles for obtaining a design.” The demonstration referred to as “showing that the flight of a man-carrying aeroplane was possible,”' was stated on page 107, “Experiments in Aerodynamics,” where Dr. Langley says, “such mechanical flight is possible with engines we now possess, since ... 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.” This statement was based upon the mistaken principle published by Sir George Cayley in Nicholson’s Philosophical Journal of November, 1809, and accepted by most experimenters thereafter, that the pressures on a plane were normal to the surface of the plane, and that the drag was equal to the lift multiplied In the tangent of the angle of incidence. Langley's actual measurements did not confirm this theory, but he assumed (page 65, “Experiments in Aerodynamics”) that if he had made certain modifications in the planes he was measuring other results would have been secured which would have confirmed it. It was this assumption that formed the basis of his demonstration that one horse-power would sustain 200 pounds at a speed of 45 miles an hour. As a matter of fact his actual measurements (page 64) showed that one horse-power could carry only 60 pounds at 45 miles an hour.
The other fundamental principle enunciated by Langley in 1891 was that known as the “Langley Law,” which was that the faster an aeroplane be flown the less will be the power required to sustain it. The fallacy of this law is well known to all aeronautical engineers to-day, but up to 1910 this was generally considered as Langley's chief contribution to the science of aerodynamics. In that year when the Regents of the Smithsonian Institution decided upon the placing of a bronze tablet in the Institution commemorating Langley's work in aerodynamics, they ordered the following legend to be inscribed upon it :—
secretary of the smithsonian institution
“I have brought to a close the portion of the work which seemed to be specially mine—the demonstration of the practicability of mechanical flight.”—Langley Aerodrome, Smithsonian Report, 1900, p. 216.
Gasoline model, August 8, 1903.
Before the tablet was cast, the Wright Brothers were consulted as to the advisability of using this inscription and they, not wishing that anything discreditable to Langley should appear on the tablet. Mr. Wilbur Wright wrote a letter to Secretary Walcott. from which the following is quoted :—
“I have often remarked to my brother that Prof. Langley was ill-fated in that he had been especially [p.307] criticised by his enemies for things which were deserving of highest praise and especially praised by his friends for things which were unfortunate lapses from scientific accuracy. I should consider it both unwise and unfair to him to specially rest his reputation in aerodynamics upon the so-called Langley Law, or upon the computation which gave rise to it, as they do not seem to represent his best work. The particular computations which led him to enunciate this law are found on pages 63-67, ‘Experiments in Aerodynamics.’ A careful reading shows that he never actually tried the experiments of which he professed to give the result. ... It is clear from the Doctor's statement that he never demonstrated by direct experiment that weight could be carried at the rate of 200 pounds per horse-power at 20 meters per second, nor that the power consumed decreased with increase of speed up to some remote limit not attained in experiment. He merely assumed that he could have done it by varying the experiments a trifle and based the so-called Langley Law on this mistaken assumption.”
The Regents of the Smithsonian Institution adopted this suggestion and the Langley Law was not inscribed on the tablet.
The article in Nature of November 3 states that “the Wright Brothers are equally clear in their acknowledgment of Langley's work,” and gives a quotation from them to support this idea. This quotation, taken in connection with the suggestion of the writer in Nature, may have carried to some readers the erroneous impression that the Wright Brothers acknowledged an indebtness to Langley for his scientific work. This was not the fact. The quotation given makes no reference whatever to Langley's scientific work. It is simply a generous acknowledgment by the Wrights at the time of Langley's death for the inspiration received from his faith in the possibility of human flight, and containing an expression of gratitude for information as to books on the subject of flight other than those they had already read. The Wright Brothers have also acknowledged their indebtedness to Chanute, Mouillard and others, but have always made it clear that their greatest debt was to Lilienthal.
Some difficulty is felt in continuing a discussion of the relative merits of the great pioneers in aviation, Prof. Langley and the Wright Brothers, since they are all entitled to our esteem, and comparison seems to be unnecessary. Mr. Griffith Brewer does not appear to dissent from such a general statement, but one suspects that his enthusiastic admiration for the work of the Wright Brothers has led him to make extravagant claims.
It is very surprising to hear that “the Wright Brothers first established a scientific basis for aeroplane design,” and that their laboratory measurements “covered a field many times greater than had been covered by the work of all other experimenters together.” The only publication cited in support of this contention occurs in two pages of the Century Magazine in 1908, and readers of scientific literature in aeronautics will realise that they do not know where to look for data based on the work of the Wright Brothers. Indeed, Mr. Brewer indicates that this must be so when he says, “While in Dayton (in 1914) I was allowed to examine, with the privilege of copying, much of the personal correspondence and diaries, as well as the records of the early purely scientific work of the Wright Brothers”; apparently the work was not publicly available. Is it then strange that one should look to Langley as the scientific pioneer, since he took the normal steps of a man of science and published complete accounts of his results as he obtained them?
Mr. Brewer refers to the “Langley Law” that the faster an aeroplane be flown the less will be the power required to sustain it. He says: “The fallacy of this law is well known to all aeronautical engineers to-day, but up to 1910 this was generally accepted as Langley's chief contribution to the science of aerodynamics.” The inadequacy of the law is evident now, but it is still at least partly true; in the case of the most modern aeroplanes the horsepower for flight decreases as the speed increases from the least at which support can be obtained. The increase of power required to increase the speed of the modern aeroplane above a certain limit is due to the light-weight engine, a factor which did not come into consideration in early practice. The error of unsound extrapolation outside the experience of the day was made, but only superficial observers could regard the enunciation of the law as “Langley's chief contribution” to aeronautical research.
One can only disagree with Mr. Brewer in his review of the situation and regret that this aspect of pioneer work in aviation was introduced in the tone of the paper on “The Langley Machine and the Hammondsport Trials.” The point of the paper was not so much missed, as suggested by Mr. Brewer, as countered owing to the fact that the statements therein did not carry conviction. One of the articles in Nature intimated this in the suggestion that the Royal Aeronautical Society should take up the matter and after full investigation issue an official report. The views on the Langley aeroplane expressed by Mr. Brewer cannot be accepted as final although given in all good faith.
- 23 Jul - short biography, births, deaths and events on date of Brewer's birth.