Art without engineering is dreaming;
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Steven K. Roberts, N4RVE
Gyroscopic Action - A Menace to Aviation

Gyroscopic Action – A Menace to Aviation

I was adopted, and my biological grandfather was an interesting fellow named Ralph M. Pearson. In his younger days, he was involved in aviation engineering, then traveled the Great Loop around the eastern US in a homemade boat before devoting his life to art. In his later years, he produced countless etchings (many with Southwest themes, as he had moved from Chicago to Taos), and also published seven books.  I wish I had met the man… his son, my bio-dad, was Ronald Hayes Pearson, a fascinating fellow as well.

Anyway, when I was 28, I tracked down my birth parents, and one of the relics of my first meeting with Ron was this self-published tract passionately decrying the evils of rotary engines in aircraft. As I have not seen this anywhere online, I felt it my duty to bring it back to life here… even though it is not my personal history, and is a subject about which I know little.

 

by Ralph M. Pearson
Chicago, Illinois – 1914

Note — In presenting to you this little booklet it is not our desire to detract one iota of credit where credit is due, nor do we wish it understood that we are criticizing any particular type of motor. While nearly all of the extracts and criticisms contained herein seem to be directed solely against the Gnome motor, we want to include all kinds of revolving motors, all motors employing a flywheel and all single propellers and tractor screws; in short, anything that generates in an aeroplane the slightest amount of uncontrolled gyroscopic torque.

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Gyroscopic Action a Menace to Aviation

Gyroscopic force seems to be so simple in its action and has been so widely accepted as a stabilizing agent, because of its adoption to the mono-rail car, that many of our scientists and engineers, who have not specially studied and experimented with it, have taken for granted that all was known about it that could be known. Certain others doubted this assumption and after a deeper study and more or less exhaustive experiment discovered that they had only learned the A B C of this peculiar force. Among the later was Prof. Harold Crabtree of Cambridge University, England, whose book Spinning Tops and Gyroscopic Action is the most thorough analysis of the subject to date. He, however, only discussed what might be termed the first phase of gyroscopic action, i. e., that which occurred when the gyroscope was anchored to the earth through one or another character of support.

It remained for a Chicago scientist and inventor, Thomas Preston Brooke, to discover that a gyroscope floating in air unsupported, the condition of an aeroplane in flight, is an entirely different proposition from one anchored to the earth. His attention was first drawn to the subject in the winter of 1906 by having the rear wheels of his automobile skid slowly over a snow covered street without leaving any tracks in the snow, thus showing that some force had lifted the rear end of a two-ton car entirely off the ground. When investigation by experiment showed him that the gyroscopic force generated in his flywheel was responsible for the phenomenon he immediately realized the tremendous importance of his discovery in its relation to aviation, in which he was deeply interested. So important did he conceive the discovery to be that he gave up his professional and business interests and devoted his entire time and his personal fortune to investigation and experiment.

Three years of research showed him that gyroscopic force aroused in a revolving motor, or in the flywheel of a motor, in an aeroplane in free flight is not only a decidedly dangerous and apparently erratic force, but that the chief source of its danger lies in a phase of its action which has heretofore been entirely ignored and seemingly unknown, namely, the acceleration of the precession of the gyroscope when in free suspension. That some of our leading scientists and engineers are in ignorance of this phase of gyroscopic action is shown by their remarks on the subject; for instance, Sir Hiram Maxim in his letter to the Scientific American of October 28, 1912, after warning against the danger, suggests an apparatus for measuring the amount of this force. It consists of a rotary motor mounted on a trunnion framework, very similar to the pivoted pedestal employed in the Gnome Company tests, and apparently does not know that his supporting framework would receive by far the greater part of the gyroscopic force.

Mr. Brooke’s work in this special field has covered a period of over six years. Up to April, 1910, he was entirely alone in his warnings against this danger; then in its issue of above date the Scientific American for the first time in print blamed gyroscopic action in the Gnome motors for the deaths of Delagrange and LeBlon. Since that time a formidable list of scientists have sounded warnings that as yet have had little effect in putting an end to the many needless fatalities.

As accident after accident occurred in which the aeroplanes behaved in almost exactly the same manner, and as no plausible cause could be found to fit, belief in the Brooke theory gained strength and the prejudice against the Gnome motor grew so great that the manufacturers were forced to place an alleged test on their motor.

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In the copy of American AERO of June 15th 1912, appeared an article that told of “actual results” obtained by “direct experiment” of Louis and Laurent Seguin, builders of the Gnome Motor, which, they claim, show that the gyroscopic force generated in a revolving motor on a turn is not sufficient to be dangerous.

If gyroscopic force actually is the deadly “unknown cause” of so many similar fatal accidents where the machine suddenly capsizes or collapses on the turn, and if the Seguin Bros., who are said to have cleared over $700,000.00 last year, 1912, from the sale of these Gnome motors, claim that their direct experiments prove that it is not sufficient to be dangerous, then they lay themselves open to one of two accusations. Either they know its true character and willfully misrepresent the facts for their financial gain, or else because of insufficient or misguided experiments they discover only partial truths and so are ignorant of their full significance. The first would be criminal, the second excusable, perhaps, but demanding correction. We all want to make flying as safe as possible and to do this we must search out the absolute truth and nothing but the full truth will serve.

Let us examine closely the report of the experiment in question. A 50 h. p. Gnome motor was mounted on a platform in such a manner that while running it could be turned in either a vertical or a horizontal direction. When the platform made a horizontal turn in 45 seconds the tendency to turn in a vertical plane (gyroscopic force) was balanced by a weight of 11.7 pounds at a distance of 39 inches from the axis. When the platform made a turn in 24 and 12 seconds the balance weight increased to 23.3 and 57.6 pounds respectively.

Book CoverNow, first and most important, notice that they admit the presence of gyroscopic force in all these experiments. Their claim is that it is not sufficient to be dangerous. Let us see: In a 12 second turn, the quickest one which they report, there is a 57 pound force to overcome. Now, M. Bouchaud-Praceig, the French engineer in Le Nature of March 4, 1911, has shown that gyroscopic force increases in the same ratio that the speed of the turn increases. A 12 second turn is a slow turn and the slow turns never have been and never will be dangerous. The turns that have been fatal and caused such accidents as those of Chavez, Blanchard, Hoxey, Moisant, Johnstone and scores of others have all happened in the fraction of a second, so quick that the eye of an observer could not see what happened. If a 12 second turn generates a 57 pound blow then a 1 second turn will generate twelve times as much or a 684 pound blow and a half second turn will generate a 1368 pound blow which would be just about enough to capsize or collapse any aeroplane that was ever built. Understand, that a complete turn is not necessary. A deflection of 6 inches or even 1 inch from the path of flight at the rate of a complete turn in one second would be sufficient to arouse the full amount of gyroscopic force.

Mr. Brooke does not claim and never has claimed that there is any excessive danger in merely making a turn, NO MATTER HOW QUICKLY, providing that the aeroplane is given the proper “bank.” His claim is that while gyroscopic action is always in evidence during any kind of a turn and manifests its presence in the aeroplane’s tendency to either rise or fall, according to the direction of the turn, it is only when a sudden gust of wind accelerates the precession of the gyroscope that the danger point is reached. This condition can also be brought about by the aviator, as the slightest abrupt movement of the controls that suddenly reduces the diameter of the turn is very liable to cause disaster. This is very easily explained by the fact that during a turn the plane of rotation of the gyroscope (revolving motor) is constantly changing causing a precession in a direction 90° from the horizontal, either upward or downward. This is the first phase of gyroscopic action and is the only one that the Seguin Brothers and other investigators seem to have found. This first phase is comparatively harmless if not molested but if given the slightest acceleration in the direction in which it is already precessing it instantly changes its plane of rotation and precesses in a direction 90° removed from the path of the first phase! It is this second phase that causes havoc, as the aviator is then taken by surprise and before he can even attempt to repel this new attack his machine has been twisted beyond his control and is on its way to destruction. The magnitude of the blow from this second phase depends principally on the abruptness of the second disturbing force.

In preparing an apparatus for one of his experiments, Mr. Brooke suspended a gyroscope in the air by a cord so that it was free to turn in any direction, the same condition as described in the Gnome experiments. When he came to test the gyroscopic force he found it so weak compared to what was felt when the gyro was held in the hands without other support that the apparatus was abandoned for demonstration purposes. He found by measurement that the supporting cord had received fully 70% of the gyroscopic strain. This showed conclusively that the action of the gyroscope in the air unsupported is entirely different and considerably more powerful than when it is anchored to the ground by any character of support. To demonstrate this in another way, Brooke placed a gyroscope in a round bottom bowl that was floating in water. Then, by a slight quick push, he changed its plane of rotation horizontally. Instantly it dove and sank. The bowl in the water very closely represents the condition of the aeroplane in the air. Any one that is skeptical can easily try this experiment and see for himself what happens.

When the Seguin Brothers say this force is not sufficient to be dangerous, the writer thinks of another actual experiment that he has seen carried out by Mr. Brooke:

Twin gyros weighing but 8 ounces apiece were mounted independently in a four wheeled frame and were set rotating in the same direction. With a hair stretched taut between his two hands Brooke gave the rear end of the gyro frame a sudden pull to one side. Instantly it reared up on its two front wheels and began to slowly precess or turn around in a circle. Quickly he struck the end that was floating in the air a 20 pound blow with his fist. The blow had no effect on it whatever, it continued its circular movement with the rear end still in the air. He then took the hair again and arrested the circular movement. It instantly dropped back on its four wheels with a thud. A rotor weighing less than a pound had generated a force more than twenty times greater than its own weight!

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For the experiment shown in the above illustrations (see page above – SKR) Mr. Brooke constructed an incline track at an angle of 30 degrees, a curve and an extension on a horizontal plane, as shown in first illustration. When one or both gyros were revolving clockwise, as viewed from the front, thus representing the high speed flywheels of reciprocating motors and motors of the revolving cylinder type, and the gyro then placed on the track at the top of the incline and released, it ran down until its direction was suddenly changed to that of the horizontal. At this point it was jerked violently to the LEFT, toppled over and plunged downward head foremost. This lest never failed to show the same results. Again, when the rotors were revolved in opposite directions, to represent the action of the BROOKE MULTI-X -MOTOR, the gyros ran smoothly down the incline and out to the end of the horizontal track without the slightest tremor or deviation.

Many have refused to accredit Mr. Brooke’s warnings simply because he is the inventor of a revolving motor that eliminates all danger from gyroscopic force and it is to be regretted that even the editors of several of our aeronautic journals refused to print his warnings on the subject and accused him of trying to obtain some cheap advertising for his motor. It would seem that when such authorities as are quoted further along in this booklet have experimented for themselves and have proved the Brooke theory correct, that the gyroscopic force generated in the revolving motors or flywheels IS the most dangerous foe to an aeroplane, it would be the part of wisdom to acknowledge the peril and try to avoid it by educational publicity rather than to engender a false sense of security by claiming that it is not dangerous.

It has been claimed by the inevitable doubters that the gyroscopic action generated in the heavy revolving motors is not in proportion to the tremendous force produced by the Brooke demonstrating apparatus. Let us see how erroneous is this conclusion by referring to some of the most eminent technicians and writers on gyroscopic action. Prof. Harold Crabtree has to say on this particular question :

“If we make the linear dimensions of everything n-times greater, we can afford to spin the gyrostats n-times slower and yet secure the same righting effect (he is speaking of its relation to the mono-rail car). This result is of great importance, for it also means that the centrifugal stresses in the real gyrostats need not be greater than in the model, and the rate of spin may be reduced from 7,000 in the model to 875 per minute in a car eight times the size.” But let us quote still another authority on this point. Prof. John Perry, M. E., D. Sc, LL. D., F. R. S., another thorough student of the gyroscope, writing of the Brennan mono-rail car, has to say:

“If the weight of the wagon (car) is multiplied by 1,000, the weight of the apparatus (gyroscope) is only multiplied by 240. In fact, if, in the model, the weight of the apparatus is ten per cent, of that of the wagon, in the large wagon the weight of the apparatus is only about four per cent, of that of the wagon.” Technically and practically, then, according to these two recognized authorities, a revolving motor with the rotating parts weighing 160 pounds need not turn over 900 revolutions per minute to produce a gyroscopic torque sufficient to right, or in this case, upset an aeroplane weighing four thousand pounds!

The Scientific American as far back as April 23d 1010, in an account of the accidents that killed Le Blon and Delagrange, both of whom were flying aeroplanes equipped with Gnome motors at the time of the accidents, states that “Gyroscopic action of the motor undoubtedly had something to do with both of these accidents.” The Chicago Record-Herald of May 29, 1912, in an account of an accident to Paul Studensky says :

“Studensky started across the field in the teeth of a puffy gale. He rose without much difficulty and when at a height of about sixty feet attempted to make a short turn to the right. Immediately his machine ended up and plunged downward, striking the earth with a terrific impact. While making a turn to the right the gyroscopic force exerted by the swiftly-revolving Gnome motor and the propeller blades, combined with the pressure of the wind under the banked wing, tipped the machine and sent it headlong to the earth. The Bleriot machine which Studensky used is the one which Earl Ovington piloted during the aviation meet at Grant Park.”

The following extract from a paper on “Gyroscopic Action” by Emil Buergin appeared in Aeronautics (American) Oct., 1911:

“It would have the same effect as the gyroscopic forces of a propeller and rotary motor, twisting the aeroplane and producing great strain on the framework.” Here are excerpts from a paper on “Gyroscopic Action in Aeroplanes” by M. Bouchaud-Praceig, read before the French Society of Engineers and published in Le Nature March -1th 1911.

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“Take, first, making a turn. In turning the rudder the aviator applies a deviating force to the axis of the aeroplane, and this, in consequence of its gyroscopic properties, refuses to obey and turns only slightly, hence, the impossibility of making abrupt turns. At the same time the second quality of the gyroscope manifests itself. The first point of the application of the deviating force, in this case the extreme end of the aeroplane, tends to displace itself vertically, that is, either upward or toward the earth, the aeroplane rears or falls headlong. These phenomena are well known by the aviators and they have a limited means of counteracting them by using, in making turns, not only the rudder but also the stabilizers. This is well and good, as long as the aviator has the time and mom to make the turns correctly, but if, for some reason or other, he is obliged to make a short turn, he turns the rudder violently and the gyroscopic force responds with equal force, the machine inclines abruptly one way or the other. If he is near the earth he has no time to react, and even at a great height, if the angle is too steep, a fatal fall is the result. A gust of wind, a passage through eddies, has the same effect as an abrupt turn and in addition the aviator is then taken by surprise. (Here follows curve charts and formulae for computing gyroscopic force, together with illustrations of his testing apparatus.) Continuing he says: “If we turn our attention to recent accidents, such for which no plausible explanations have been furnished, it will be seen generally that the accident occurred in making an abrupt turn, and often, that the aeroplane has fallen headlong without any apparent reason. This was the case with Chavez, LaFont and Blanchard after they had made long flights without accident.” Albert Kapteyn, Pres. of Dutch Aero Club, who in a very comprehensive paper on the subject, printed in Flight (English) Nov. 19th 1910, said among other things:

“Even though a pilot may take precautions to the extent of not voluntarily turning too quickly, nevertheless in windy weather the action of the wind itself may force the machine to suddenly change its position and thus bring these very gyrostatic forces into exaggerated effect.”

“It is notorious that several fatal accidents have taken place recently under circumstances of this sort.” (Note the date of this paper and consider the scores of fatal accidents that have since occurred under similar conditions.)

Professor H. H. Turner, Chairman of the British Assn. says: “Dr. Shaw has shown how much the meteorologists have to say on the question. I myself have been struck with Mr. Berriman’s experiments with the gyroscope, which indicates that if an airman turns in one direction the gyroscopic action of the engine will tend to make him rise, whilst if he turns in the reverse direction the tendency is to make him dive. I myself have unfortunately seen one aeroplane accident in which the airman fell in turning, and it is quite possible that gyroscopic effect was responsible for the disaster.” (English Aero Oct. 1911.)

Mr. Griffith Brewer in Flight (London) Jan. 11, 1913, says: “In all cases a rotary engine would appear to increase the danger, because the wings in twisting find themselves opposed by a more unyielding base than would be in the case with an engine having no gyroscopic effect.”

Mr. E. K. Scott, another noted scientist and engineer, a member of the British Association, stated that he had had experience with the Brennan mono-rail car and felt quite sure that many of these (aeroplane) accidents, which so far were unexplained, can be explained by gyroscopic action in the engines. (English Aero Oct. 1912.)

Mr. Howard T. Wright, one of the world’s pioneers in aeronautical engineering, in a lecture recently given before the Coventry (England) Engineering Society, also published in Aero (English) Dec. 1912 says: “In steering the Farman biplane to the left there is a distinct tendency for the machine to dive, and in steering to the right to climb. Some people have put this down to the propeller torque, but it has really nothing whatever to do with it. It is a question of gyroscopic reactions set up by changing the plane of rotation of the revolving Gnome motor.”

The Chicago Daily News, Sept. 13, 1912, says: “The lesson of Paul Peck’s death has sunk deeply into the minds of men apparently and today there is much talk of gyroscopic action and how to counteract it. Gyroscopic action is supposed to have played a part in Peck’s fatal accident.”

Stanley Y. Beach, a frequent contributor to the Scientific American, in a letter printed in that magazine Oct. 12, 1912, relating to gyroscopic action in aeroplanes, says: * * * “The only time at which this force acts to a dangerous degree, is when an aeroplane moving in a straight or curved course is suddenly twisted about to right or left. This sudden deviation from its course need be through only two or three degrees, but it instantly reacts, causing the machine to turn upward or downward with a suddenness that, in the latter case, the aviator is flung from his machine like a stone from a sling. John B. Moisant at New Orleans and W. A. P. Wiilard (Miss Quimby’s passenger) at Boston, are examples of this action. A sudden twist may be given the aeroplane in several ways, such as the pilot’s foot slipping off the tiller, or the breaking of a control wire, or upon entering an “air hole” or “pocket.” Under these conditions, for a moment, the pilot is perfectly helpless, but if he is securely strapped to his seat he has some chance of recovery. With a 100 horse-power, 14-cylinder, revolving motor that are now being used, the reaction may be so intense as to break the fuselage in two.”

The Brooklyn Eagle, June 23, 1912, says: “Probably over 75% of the accidents that happen to aeroplanes are due to hidden dangers that lurk in the modern high speed motors. Experts are just now beginning to bend their energies upon the elimination of that peculiar action of bodies revolving at high speed called gyroscopic force.”

Mr. Orville Wright, in Aeronautics (American) Nov. 1912, says: “If motors could be entirely non-gyroscopic, it would be an advantage. Gyroscopic effect of the heavy revolving motors is no doubt quite troublesome as it effects the balance of the flying machine. Every time the course of the machine is changed either upward or downward, the gyroscopic effect of the motor causes one wing to be raised and the other wing to be depressed, and every time the machine is struck by a wind gust which lifts one wing, the gyroscopic effect of the motor causes the machine to either turn upward or downward, according to the direction of rotation of the motor.”

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Sir Hiram S. Maxim’s letter printed in Scientific American under date of Oct. 26, 1912, in speaking of the Gnome motor, says: “This engine is of considerable weight and practically the whole of it revolves at high speed in the same direction as the screw or propeller. There is no question about it, these high rotating parts do produce a very powerful gyroscopic effect.”

One of the ablest treatments, technically, given this important subject was the paper by Baron E. Adrain Von Muffling and published in Fly April 1912. The following are some extracts from this paper:

“When a famous rotary motor first became popular it was often stated that the gyroscopic action due to the revolving mass would tend to keep the plane on an even keel, automatically. As a matter of fact, it does everything to upset it.”

“Gyroscopic action does not prevent a force from changing the direction of a body, as is widely supposed, it merely changes the direction in which the force acts.”

“A rotary motor, or fly-wheel of a stationary motor, mounted in an aeroplane in flight presents a condition which is impossible to reproduce in a laboratory; that is, the condition of a body entirely free from direct support, and free to move in a three dimensional direction.”

“The result being that the aeroplane is bound to follow the gyrations of the motor.”

“It is the greatest enemy, an enemy whose power we do not yet sufficiently realize. And I repeat, its usefulness in solving the problem of stability will be mainly in showing us what to avoid.”

Perhaps the most emphatic warning against this grave danger is given in a letter from J. W. Cloud, Chief Engineer in England to the Westinghouse Co., and published in London Flight Sept. 6, 1913. The letter, in part, follows (the italics are ours) :

“Although automatic stability against various disturbances may be desirable of accomplishment, it would appear that a construction which would avoid automatic instability is not only more desirable, but is entirely easy of accomplishment. The automatic instability referred to is the result of the deflecting forces which are generated by the rotating masses of the engine and the propeller when the orientation of the axis of that rotation is changed, either by a sudden puff of wind or by the manipulation of the pilot in steering. In given circumstances, otherwise, the magnitude of these deflecting forces is directly proportional to the rate of change in the orientation of the axis of rotation, so that the degree of instability may readily be doubled or quadrupled or increased manifold by the relative suddenness of the gust of wind, and it may be beyond the power of the pilot to so manipulate his machine as to prevent actual overturning. Even when he can manipulate the machine so as to prevent overturning, these deflecting forces throw sudden strains upon the framework of the aeroplane between the engine and the supporting wings, and upon the wings, or supporting planes themselves, which, as now constructed, must finally resist these deflecting forces, or break in the effort to so resist them.

Out of the conflicting evidence of eye-witnesses of the two recent army aeroplane disasters, one can readily believe that both of the aeroplane frames were wrecked, or their sustaining planes were broken, by the sudden deflecting forces thrown upon them from the rotating machinery, due to an unusually quick change in the direction of the axis of rotation of the driving mechanism; the pilot endeavouring to resist these deflecting forces by manipulation to prevent being tipped over, and thus throwing sudden strains upon the aeroplane frame and the supporting planes.*

(*The makers or the Wright Brothers aeroplanes have rested sicure In the thought that by rotating their twin propellers in contrary directions they were eliminating gyroscopic action, when, as a matter of fact, by so doing they merely threw Into the frame of their aeroplane the stresses set up by gyroscopic action, thereby causing great danger from collapsing planes).

The dynamics of rotation is well understood, and mathematicians and mechanicians are as fully aware of the existence of the deflecting forces above referred to as they are of any other facts of mathematical and mechanical science. It is well known that the magnitude of these deflecting forces is proportional to the product of four factors, viz.:—

m The mass rotating; the square of the radius of gyration; w, the angular velocity of such rotation; and a, the angular velocity of change in the orientation of the axis of rotation.

It is also well known in which direction the deflecting forces will act, and that they will cause the forward part of the aeroplane to tip downward in the case of turning in one direction, and to tip upward in the case of turning in the opposite direction.

As the mass rotating is one of the factors which determines the magnitude of these deflecting forces, it will be clear that with the use of the Gnome engine, in which the cylinders rotate as well as the propeller, these deflecting forces are increased by the increased mass of rotation over what they are when driven by engines in which the cylinders do not rotate, but only the crankshaft of the engine, together with the shaft itself and the propeller. Further, when a Gnome engine of 80 h. p. or ioo h. p. is employed, instead of only a 50 h. p., it follows that the greater mass rotated in the engine cylinders themselves, to say nothing of the increased mass of the propeller, if it should be increased, will correspondingly increase the deflecting forces with the same rate of revolution of the machinery and the same rate of change of direction of its axis of rotation.

It should not therefore seem strange to one who is familiar with the forces generated in such cases that the aeroplanes in question should have been broken in the effort to resist the deflecting couples, under the conditions of flight which prevailed. The high power of the engines used and the facts of observation by onlookers that the aeroplanes changed their direction rather suddenly would point to these deflecting forces as the actual cause of the accidents.

A careful following of the various accidents in different parts of the world for the past three years leads the undersigned to believe that far more than one-half of the casualties which have occurred by men falling to the ground in aeroplanes are traceable directly to this automatic instability, which has been improperly allowed to form a feature of the construction of the propelling mechanism of the aeroplanes. It seems probable that the time is not far distant when it may be held to be just as criminal to permit servants of the public to fly with machines so constructed as it would be to place unsafe powder in the magazines of battleships—viz., powder which it is known will explode at temperatures which are sometimes reached in such magazines, since the remedy for the one danger is as simple as the remedy for the other, and it will be held to be the duty of all responsible officers to be familiar with the remedy and see that it is applied in the construction of aeroplanes for national purposes.”

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“Of course” say some of our aviators, “we all know there is gyroscopic force in a revolving motor, but it is not sufficient to be dangerous and can easily be overcome by the controls.” When every one is agreed that this force is present in a flyer and has to be reckoned with, why argue that it is not dangerous because it can be overcome by the controls? Certainly it can be overcome by the controls and counteracted nine times out of ten when the aviator is quick enough, but some day the tenth time comes, the turn or toss is too sudden, the force is just a trifle too strong for the controls and we read of another “unknown cause” fatality where the machine collapsed or capsized and dove head first.

Becoming alarmed at the numerous unexplained accidents that were occurring to the monoplanes, the government of France a few months ago prohibited flying on any of its hundreds of army aeroplanes of this particular type. These monoplanes, with a very few exceptions, were driven by Gnome, or other revolving, moters. The government appointed a committee of “experts” to enquire into the cause of these accidents. After examining all the various makes of monoplanes, this committee sent in a report recommending the strengthening of cables, wing spars and fabrics, and in some cases, advised the changing of the controls. Thereupon the government issued an order to the manufacturers demanding that these changes be made at once. After thoroughly overhauling all the monoplanes and making them comply with the new order, the ban was raised and the monoplanes were again permitted to fly. But instead of lessening the number of accidents, they have occurred with greater frequency than before. This should prove conclusively that the true cause had not been discovered and removed.

England had exactly the same experience with her Monoplanes and in the report of its investigating committee the important question of danger from gyroscopic action was disposed of in short order by saying that “calculations” were made on a 100 h. p. Gnome motor and propeller, “assumed” to be running at 1200 r. p. m., and states that

“The moment due to this cause is then of the order of magnitude of that which would be produced by a force of 20 lbs. acting on the horizontal or vertical rudder.”

“In its relation to steering, the effect may be compared with that of a small gust of known direction, and should cause no difficulty to the flyer.”

Flight (London) Sept. 20, 1913, contains a letter from Mr. Jno. W. Cloud, in which he shows that the English committee erred in their calculations due to the lack of knowledge of the true conditions of aeroplane flight. The complete letter follows:

“In view of the character of the issues involved, it will probably be conceded that the definite statement in the report of the Monoplane Committee, to the effect that there is no reason for alarm from this source, does not remove this question from the sphere of proper discussion, since it would be equally deprecable to attempt to spread a general impression of safety from this or any other source, without satisfactory proof.

Assuming with this article for the moment, that the elevator offers all of the resistance to the precessional couple about the horizontal axis, and assuming that the figures there given represent the facts in a general way, as is evidently intended, it seems pertinent to enquire, how is the resistance of 2 lbs. per square foot on the 10 square feet of elevator surface, or a less amount on a larger surface, to be called into action, even when the pilot is forewarned?

Remembering that this resistance must act perpendicularly to the 20 ft. of leverage assumed, which in general is horizontal, it will be seen that the resistance must in general act in a vertical direction. To obtain such resistance upon the air, the elevator must be tilted to a degree dependent upon the circumstances, but sufficient to secure a vertical component aggregating 20 lbs, upon the surface. The horizontal component will act to retard the progress of the aeroplane.

Just how a vertical component of 20 lbs. is to be secured mechanically whenever needed, it is difficult to see. It should certainly be co-incident and coterminous with the precessional couple in order to be properly effective. If this be had by a mechanical connection to the lever operating the banking, it will not always be right, because the vertical component with any fixed degree of tilting of the elevator will be a function of the speed of the aeroplane relatively to the air. Since this relative speed is not always the same, even in a calm, and since it varies still more in wind, and since in the case when wind is blowing it is constantly varying as the aeroplane changes direction, it becomes practically impossible for the pilot to properly operate it at every instant, and the only safe way is to make the mechanical arrangements so that no such unbalanced couples will occur at any time. This will result in safety from this source, not only when the pilot is forewarned, but also in the more dangerous case when he is suddenly diverted from his course by an unexpected puff of wind, and this will be true whatever be the magnitude of the precessional couples, viz., whether they are confined to the limits assumed in the article in question or not.

To obtain a resistance of 2 lbs. per square foot on a plane of 10 sq. ft. area, it will require that such a plane should move in a direction perpendicular to its surface at a rate of about 30 ft. per sec, and in the case of sudden turning without the elevator being tilted, it will be evident that very little resistance would be offered by it, before the aeroplane had turned over 90° about a horizontal axis.

The construction required to effect the result of automatic counterbalance is another matter. Manifestly it would be ill-advised to introduce new dangers worse than those sought to be removed, but the existing faults should at least be recognized without undue alarm, and should be rationally corrected.

JNO. W. Cloud
York Road, King’s Cross.

Gyroscopic page 8

A number of the most prominent aviators on this side of the water have acknowledged the presence of this dangerous force. Among the number are Max Lillie, DeLoyd Thompson, Arthur Stone and Capt. Tom Baldwin. Less than two hours before his fatal accident Paul Peck, in a conversation with Mr. Brooke, acknowledged that he felt the gyroscopic action in his Gyro motor but said that he did not consider it dangerous. Otto W. Brodie, who had undoubtedly made more individual flights during the past four years in a Gnome motored aeroplane than any other flyer, recognized the danger from gyroscopic force. He had had numerous narrow escapes from upsets and head dives and after some particularly bad twist would say: “That motor will get me yet.” Brodie had arranged to place the new Brooke non-gyroscopic motor in his Farman machine and was looking forward with much satisfaction to getting away from gyroscopic force in his machine, or, as he expressed it, “having a motor that won’t have to be watched on the turns.” Mr. Brodie was killed by his machine plunging head downward.

Various features of the near future aeroplane, the machine that will be inherently stable, are rapidly being developed. This is all very good, but these improvements are only directed against the dangers that beset the aeroplane from without and do not in the least obviate the danger coming from the inside, from the very heart of the machine. We can never hope to obtain anything like safe flying until we eliminate from our aeroplanes every ounce of gyroscopic action, even to that generated in the tractor screws and propellers.

RALPH M. PEARSON,
225 So. Wabash Ave.,
Chicago, III.

Resources

Earl Ovington took issue with Ralph Pearson’s line of reasoning in the November 30, 1912 Scientific American Supplement.