Читать книгу The Rise of the Flying Machine - Hugo Byttebier - Страница 40

Chanute and Herring (1895/1901)

The American Engineer and Railroad Journal was edited and published between 1886 and 1896 by Matthias Nace Forney, an old friend of Chanute’s. Before publication was discontinued, Forney organized an aeronautical supplement to the journal entitled Aeronautics for which Chanute acted as assistant editor and in which, from October 1893 to September 1894 all the papers and discussions relating to Chanute and Zahm’s “Conference on Aerial Navigation” were printed. This supplement continued to be published until October 1895.

During 1894 and 1895, Chanute, in addition to his correspondence with some 200 aeronautical enthusiasts living all over the world, gave lectures on aeronautics. During these he tried to instil some of the enthusiasm for human flight that drove him, and he encouraged his audience to take up Lilienthal’s flying experiments in the US, thereby helping to bring about the advent of human flight.

During one of these lectures he was taken to task by one of his audience who argued that it was easier to persuade others to take up experiments that were not devoid of risk than to do it oneself. Chanute, honest as he was, saw the point and decided to act. But he was then 63 years old and it was obvious that he could not himself fly, so he secured the help of several young men and organized the first gliding experiments in the USA.

The example they proposed to follow was clearly Lilienthal’s, but they were also interested in making improvements. According to Chanute the most important quality of any aeroplane was the maintenance of a correctly balanced flightpath.

In the conclusion to Progress in Flying Machines Chanute wrote “the problem of the maintenance of the equilibrium is now, in my judgment, the most important and difficult of those remaining to be solved”. And he went on to stress the fact that “no amount of motive power will avail unless the apparatus to which it is applied is stable in the air”. This echoed what Hastings had set out in 1893.

All through his book Chanute insisted on this theme, using all the synonyms he could find: balance, stability, equilibrium, equipoise, adding “stable equilibrium” and “automatic stability” for good measure.

Stability and balance are not synonyms, however, and Chanute in this respect, like many of his contemporaries, was not very clear in his concept. What he really sought was stability. Inherent stability indicates that, when a flying machine deviates, for any reason, from its normal flightpath, it will revert to it of its own accord without the intervention of a human controller or of an automatic controlling device like a pendulum or gyroscope.

Inherent stability can only be obtained by the judicious placing of fixed auxiliary surfaces, like the Pénaud tail or a dorsal fin. Instability, as the word implies, is just the opposite and means that a flying machine that is deviated from its flightpath will not revert to it except by using controlling devices that have nothing to do with stability but are the means for changing a plane’s course in the air. These devices are movable surfaces, such as rudders, elevators and ailerons.

These controlling devices are essential to correct abrupt or unforeseen deviations with which an inherently stable system is unable to cope. It is in the difference between stability and control that the confusion started. A stable aircraft needs additional means to control it, but an unstable aircraft relies entirely on control to prevent it from tumbling out of the sky.

This means that a stable aeroplane will fly by itself. It can be argued that it is possible to fly an unstable aeroplane provided a skilful pilot is at the controls and is continually able to correct the irregularities of the flightpath. And it is true that aeroplanes have been flown that way, but not for long.

It must also be understood that stability and control in a way interfere with each other. A very stable plane cannot make swift changes in direction whilst a supersensitive plane will be less stable, but is also more manoeuvrable. For example birds are perfect flyers. No bird is inherently stable and its flightpath is forever conditioned by its lightning reflexes and instinctive reactions working on the nearly infinite possibilities for positioning wings and tail. But a kite, as opposed to a bird, has to be stable or it will not fly. Therefore true bird flight will forever be denied to man and this was clear to the really knowledgeable pioneers, among whom Cayley, Pénaud and Hargrave rank as the most clearheaded.

All this was not so obvious to many other experimenters who somehow regarded bird flight as the ideal to strive for — some even went to the extreme of stating that “an aeroplane of rigid form is unnatural” which may be so but then also so is a wheel. The result of this line of thought was that many pioneers were busy looking for the possibilities of putting the necessary controls on the flying machine so that the pilot would remain master of the plane’s movements. This proved to be an illusion and a dangerous one at that.

To Chanute, the balance or equilibrium which he so eagerly sought meant longitudinal stability. Pénaud had already solved this problem but Chanute was not wholly convinced, because the Pénaud system absorbed power and Chanute had noted that in France not much interest was shown in following Pénaud’s example (with the exception of Tatin), and to expend power for the sake of stability when there was not even enough available for sustentation did not seem to be an intelligent proposition at that time.

Through his research and his correspondence with Mouillard, Chanute had been won over to a system of flexible surfaces “which will give the greatest amount of stability to a kite by producing automatic adjustment to the wind’s varying intensity”. This seemed to be a good idea but “a great amount of stability” was just what flexible surfaces were not able to provide.

The greatest misjudgement Chanute made, however, was in assuming that Lilienthal not only controlled but also balanced his glider by bodily movements. However, this was not the case, although it is true that Lilienthal, after 1895, did toy with the idea of introducing movable surfaces for better balance. This may even have caused his fatal crash. Referring to Lilienthal in Progress in Flying Machines, Chanute had stated, “the necessary apparatus to fly consisted of properly constructed sustaining surfaces, skilfully operated”. The reference to skill was made many more times before a truly stable aircraft was finally introduced more than ten years later.

Among the US experimenters of the 1890s it would seem that only Langley saw the aeroplane as it really was — a vehicle using the air instead of the ground as its supporting medium — as Cayley had described it in 1809. And, since it was intended as a vehicle for transporting human beings, the overriding need was for stability in the same way that motor cars, railway trains and bicycles need smooth surfaces to travel over. Only acrobats use unstable means with which to move around in order to impress the crowds and so earn a living.

Added to this there was a more decisive factor in favour of inherent stability — a factor that was completely overlooked by the early pioneers — and that was the necessity for stability in case flying speed was lost. In the case of a stall, resulting from engine failure or any other cause, a stable aeroplane will automatically turn into a glider and, switching to gravity as an alternative source of power, it will regain flying speed by losing altitude and glide safely to earth. In an unstable craft, once minimum flying speed is lost, nothing can be done to save it, just as a stricken bird is unable to make an emergency landing.

To Chanute, the necessity for absolute inherent stability was not yet evident; he was still confused by having absorbed too much conflicting information. He thought that Pénaud’s seemed to be a good solution, but he was also fascinated by Mouillard’s ideals5, but the two solutions were contradictory.

With regard to transversal (lateral) and directional stability, these were accepted by Chanute as a matter of course and he considered that they were to be obtained by using a dihedral angle of the wings and a vertical keel (or fin). In his book he made no reference to lateral and directional control by ailerons or vertical rudders for steering (or “guidance in any desired direction” as he formulated it). He was content to point to Lilienthal’s manner of shifting the centre of gravity by bodily movements.

At the end of 1895, Chanute secured the services of Augustus Moore Herring who had just resigned from his undertaking with Langley. Chanute and Herring had been in correspondence earlier, in fact Herring had built several varieties of model gliders which Chanute designed when he was casting about for a workable configuration, and the new association worked quite smoothly at first.

It is interesting to note that Chanute and Herring saw eye to eye in their belief that an aircraft should be balanced by movable surfaces. Herring, in an article published in the Aeronautical Annual of 1896, described a little tandem-wing model aircraft he had built in 1890 and launched from a long table by pulling it with a string. This model aeroplane possessed a moving horizontal rudder (elevator) that was regulated by a pendulum in tests and was thought to be able to balance the aircraft properly in flight.

Previously in 1884 Goupil had proposed a system actuated by a pendulum but there is no reason to suppose that Herring had ever heard of Goupil’s proposition because it often happened that different pioneers, who were unconnected with each other, were inspired with the same ideas. The most interesting result that Herring obtained when flying his model plane was that it flew “unmistakably better” when the pendulum was inoperative than when it was free. Here was further proof that an aircraft flies better when inherent stability is obtained by fixed surfaces than when a controlled equilibrium by moving surfaces is attempted. But the urge to regulate the flightpath proved too great and the lesson was lost on Herring who, in his article (like Chanute before him) pointed to the theory that “the securing of stable equilibrium is perhaps the hardest problem of all”.

As soon as they set to work together, Chanute and Herring tested a few models and then built a composite kite consisting of the grouping together of several kites, due to its resemblance to a stepladder, the “ladder kite”. This apparatus performed very well and it was decided to build a similar larger one which would be capable of carrying a man. In order to proceed from an actual flying glider it was decided first to rebuild a modified Lilienthal-type glider that Herring had built and tested from the highest point of land in New York City in or near the Bronx during 1894.

In June 1896 Chanute and Herring travelled with the man-carrying kite and the Lilienthal-type glider to the deserts and dunes of the south end of Lake Michigan, about 30 miles from Chicago, and there they set up camp. They were accompanied by two assistants, William Avery and William Paul Butusov, and were later joined by a Dr Ricketts. Butusov was there mainly to test a large albatross-like glider that he built at Chanute’s expense but which, sent off twice in ballast, proved a failure.

After Herring’s Lilienthal-type glider was first erected on the 22 June a few gliding tests were made, but it was found that “the operator had to shift his position as actively as a tight-rope dance but to greater distances, to avoid being overturned”. Chanute believed that the differences in flying behaviour between their Lilienthal-type glider and the original were due to Lilienthal’s skill “developed by four or five years of practice”. But the difference lay not so much in Lilienthal’s superior skill but in the fact that Lilienthal had at first experienced the same difficulties in maintaining balance and had then developed his glider into an inherently stable machine.

“After having been broken and mended a number of times” the so-called Lilienthal glider was wrecked beyond repair on 29 June and “discarded altogether”. “Glad to be rid of it” wrote Chanute in his diary that evening.

The second machine, based on the ladder kite, was erected on 23 June and it consisted of “six pairs of wings superimposed and trussed together; pivoted at their roots upon a central frame, the lower chord of which was spread open to receive a man at the center”. The aim was “to study equilibrium and that alone” as Chanute later wrote and the pilot was expected to steer by moving his body in the Lilienthal style, “stability to be maintained by the movements of the wings above him, which swung on their pivots back and forth restricted by rubber springs”. Chanute thought that it would be better to balance the aircraft by moving the wings instead of the body, or to use his own words “it might be preferable to provide moving mechanism within the apparatus itself”. He thought that this was a better system for maintaining balance than the “first method tested in which the man moved and the wings remained fixed”. But during the trials it was soon found that what had worked as a fixed-wing kite did not work very well in the man-carrying version. All those moving wings were not leading to stability at all and on 29 June the grouping of the wings was changed to four pairs in front and two pairs at the rear to serve as tail.

On 1 July the machine was again remodelled as a quinqueplane with one set of wings to the rear. This new shape was given the nickname “Katydid” and Chanute found that this glider worked best of all. The tail was made flexible and vibrated up and down. Some 200 glides were made with this machine, but Chanute’s associates were not completely satisfied because the operator still had to move a great deal and the decision was taken to reconstruct the multiple-wing machine completely and to design and build a new one. They then broke camp and returned to Chicago.

During July and August 1896 the multiple-wing machine was again rebuilt with four pairs of wings in front instead of the former five, even though weight was a problem and the multiplicity of wings was felt to produce too much drag. Meanwhile a new triplane glider was designed by Chanute and Herring jointly and the working drawings were made by Chanute. The important change was that the wings of the new triplane were fixed and were trussed together in order to obtain strength and rigidity. As a former expert builder of bridges Chanute used the Pratt truss which was the best construction form when the goal was to combine strength with economy of material and so to achieve light weight. It was the first time the Pratt truss was used on a flying machine and it remained the standard for all triplanes and biplanes built thereafter.

The triplane’s frame was of spruce and the surfaces were covered with varnished Japanese silk. It was a modern construction and weighed 33.5 lbs with a wing surface of 143.5 sq ft.

The new glider incorporated a flexibly-mounted tail boom, restrained by springs, to dampen the effects of gusts. While Chanute credited Herring as the inventor of the elastic tail, he nevertheless gave Avery credit for perfecting it. Chanute sometimes referred to this tail as a Pénaud tail with an angle of seven to eight degrees to the main surfaces, but Herring corrected him on that point in a letter dated January 5 1902. The purpose for making the tail instead of the wings movable was basically the same, to cope with sudden gusts of wind and maintain the craft’s balance.

Chanute’s party returned to the shores of Lake Michigan on 20 August. Many glides were made with the quadruplane and greater distances were covered than with the former quinqueplane.

When the fixed-wing triplane was tested it was found that the lower wing got caught on the ground and on 31 August it was decided to remove it. The two remaining wings were then connected together “by a girder composed of vertical struts and diagonal ties” and so became the strong and light biplane construction that remained in use until the end of the 1920s. Its wing surface was 135 sq ft and to honour Herring’s work in connection with it, Chanute at first called it the “Herring machine”, much to the latter’s gratification.

As it had fixed surfaces and a tail that would only move when strong pressure was applied, the triplane which had very soon become the biplane glider, flew much better than anything they had tried before and Herring and Avery made some 2,000 beautiful glides in this machine. Herring’s longest was 360 ft in fourteen seconds. It was also able to fly in winds of up to 31 mph, stronger than anything Lilienthal had dared to tackle.

Hitherto, the relations between Chanute and his associates had been all that could be wished for, but Herring’s character again asserted itself and on 13 September he confided to a reporter about a disagreement with Chanute, whereupon Chanute, like Langley before him, made no effort to keep him. The reporter thought that Herring’s attitude was prompted by egotism and jealousy. According to Herring, he left because he objected to the test of the Butusov glider, which he considered unsafe. But Chanute wrote that Herring left “because he thought that he would be able to solve the problem of human flight singlehanded... In order to be alone in reaping future rewards”.

In spite of these personal problems, Chanute, who was a very patient and mild-mannered man, remained on friendly terms with Herring, who then found a new backer in Matthias C. Arnot, a young banker from Elmira who had tried gliding and was very interested in aeronautics.

With Arnot’s help Herring built a slightly smaller version of the Chanute-Herring biplane of 1896. The new Herring-Arnot glider was tested at a new Indiana Dunes location with excellent results. Chanute was present in an advisory capacity for several of the tests held between 13 and 17 September and 1897, when a number of photographs were taken. On the last two days James Means was present and he proposed to Chanute that they should build a powered aeroplane based on Chanute’s designs, but Chanute refused because he did not want to become involved in another quarrel. Chanute knew that Herring felt he had designed the “automatic regulator” and he would not use it without Herring’s consent. “He is so sensitive,” wrote Chanute to Means, “and has so many illusions as to the value of the device that the praise you unduly bestow on me and the hint that he might be left out might cause him to boil over.”

On 20 October 1897 Chanute read an address at the Western Society of Engineers in which he described his gliding experiments of 1896, and at the end of the address he introduced Herring and asked him to describe the pictures taken during some private glides of Herring’s the previous month. Herring did this very ably and told the audience that his best attempt had lasted 48 seconds. The most interesting part of these gliding experiments of 1896 and 1897 was that they were never marred by any accident.

In 1897 Herring claimed that he had covered 925 ft on a new triplane against a 48 mph wind in the “late fall” of 1896. But, apart from Herring’s statements, no other corroboration of that flight has been discovered.

The fact that the biplane gliders continued to be referred to as “Chanute gliders” was not to Herring’s liking. He also objected to Chanute’s use of the photographs of the Arnot-Herring glider to illustrate several lectures he gave. The reason that Chanute used the 1897 photographs instead of the 1896 ones was because they were of much better quality than those taken the year before. As the two biplane gliders were very similar in all their particulars, Chanute could hardly be accused of bad faith in preferring the better pictures.

Meanwhile, Herring, who was a very talented craftsman, had studied the question of power and had built a small two-cylinder motor driven by compressed air from a container filled at 600 lbs/sq in. by an outside compressor. He also applied for a patent under his name that was turned down by the Patent Office. In the May 1897 issue of Horseless Age Herring described the future flying machine as he saw it and concluded that “the time is near when power may be added”.

With Arnot’s backing, Herring then built a new and bigger aeroplane based on the biplane glider of 1897 and powered by his compressed-air motor, which he thought capable of delivering between 3 and 4 hp for about 8 to 10 seconds. During the experiments with Chanute, calculations had been made that showed that horizontal flight could be achieved as soon as an engine of 5 hp was available.

In the autumn of 1898 Herring’s powered biplane which he labelled “Experimental Flying Machine” was ready for tests. It weighed 88 lbs, and had wings of 162 sq ft surface. On 10 October a successful test was made; the plane covered 50 ft in the air against an estimated 25 mph headwind. The wind had been sufficiently strong to take care of take-off and the plane covered 50 ft of level travel when Herring raised his legs after taking a few steps. Thereupon Herring wired Chanute to come to St Joseph on the opposite shore of Lake Michigan to witness the next attempt. Chanute took the boat that same night, but when he arrived all efforts to fly failed because a borrowed stationary engine powering the compressor broke down and Herring could not pressurize the air tank. Herring’s bad luck remained true to form.

Chanute was disappointed and also disinclined to believe the story of the 50 ft flight made earlier that day, nor did he believe the story of another attempt made on 22 October in the presence of casual (not official) witnesses, when Herring supposedly covered 73 ft. These two flights may well have taken place, considering the aerodynamic factors involved and Herring’s undoubted capacity but Chanute — rightly — wrote to him later that “such performances must be repeated many times to be convincing”.6

The next step for Herring to take was to study the internal combustion engine so that he could build a powered aeroplane with a gasoline engine. He had experimented with a two-cylinder gasoline engine in 1897, but could not obtain the power necessary for flight and by 1899 he had further built a single-cylinder 8 lbs steam engine. He was also busy with a series of gasoline-powered single and tandem bicycles (“Mobikes”), that he hoped would start Arnot and him in the motorized vehicle business. But he continued to be pursued by bad luck as he lost most of his engines and patterns when the Truscott Boat Mfg. Co. of St. Joseph, where his material was stored, was gutted by fire on 10 October 1899.

His backer M. C. Arnot did not lose faith in Herring’s capability but he died on 31 July 1901 after an operation for appendicitis, and the money he had promised Herring from a life-insurance was not paid when it was ascertained that the policy had lapsed the day before Arnot passed away, leaving Herring with several accumulated partnership debts.

This was another blow, but Herring’s courage, self-confidence and resilience never waned, not even after Chanute wrote to him (on 24 March 1901): “I scarcely think that what you have accomplished during the last three years would warrant me in setting your work above that of Tatin, Hargrave, Langley and others as you seem to desire.” Chanute had written this in reply to a “high-toned” letter he had received from Arnot, accusing him of ignoring Herring’s achievements in an article for the Encyclopaedia Britannica that was illustrated with photographs of the 1897 Herring-Arnot glider.

In spite of all this Herring was able to continue his work on powered gliders whilst Chanute continued to lecture, counsel and write, as well as build gliders. Then, during 1902, both Chanute and Herring became involved with the work of one of the most formidable personalities in the whole history of aviation.

5. Chanute, at the time when his book was being published, was busy with the application for a patent in Mouillard’s name which proposed a warping of the wing tips in order to provoke a powerful turning movement. The patent was applied for in 1892 and issued in May 1897. Chanute also sent Mouillard money for a glider to be built according to his ideas, but nothing came of it and Mouillard died on 20 September 1897.

6. This is a statement that is still valid and should be taken to heart by all historians keen to make claims for alleged but unproved “first flights” that were never repeated nor officially witnessed.