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Aviation History
1912
1912 - 0925.PDF
OCTOBER 12, 1912. [/UGHT] CORRESPONDENCE. V The name and address of the writer (net necessarily for public***,) MUST in all cases accompany letters intended for insertion, or containing queries. Correspondents communicating with regard to letters which have appeared in FLIGHT, would much facilitate read? reference by quoting the number of each letter. Stream-Lining the Rudder. [1643] There seems to be a general impression that machines of the Nieuport and Hanriot type are subject to side-slips and nose dives, and, further, that owing to the peculiar stream-line of the body, the rudder and elevators are liable to be screened as a result of the abnormal speed attained during the latter condition. The case quoted is that of Capt. Loraine, who over-banked with a failing engine. Half-an-hour previous to his fatal accident he had a side-slip, followed by a nose-dive from approximately 1,000 ft., but was able to recover before reaching the ground. His death was caused by the same thing from about 500 ft., from which height he was unable to straighten up. The only other case is that of Edouard Nieuport, who found it necessary to bank steeply to avoid some trees. He was coming down eti vol plane, and his engine refused to pick up. There was a gus,ty wind b'owing at the time. These are the only cases of nose-dive or side-slip on this type of machine, and as they are so easily explained, perhaps it would be as well to point out that the above impression is entirely without foundation. Surely one can credit such men as Edouard Nieuport and Pagny with having taken into account the bare chance of the controls being negatived when designing their stream-lines. Brooklands Aerodrome. SYDNEY O. SIPPE. Gyroscopic Force in Aviation Accidents. [1644] I don't wish you to think that I am trying to monopolise your correspondence columns, but there is another matter in your very interesting issue of FLIGHT, dated August 24th, upon which I should like to touch. The letter in question is that from Mr. Thomas Preston Brooke of Chicago. His letter (1612) is headed " Gyroscopic Force in Aviation Accidents." A great deal has lately appeared in the aeronautic press in this country on this gyroscopic " bug-a-boo." As I think the greater portion of it is all nonsense, I have done my best to correct the ill- effects of letters circulated by those who know nothing about the subject from a practical standpoint, or else who have " an axe to grind," and hence whose opinions are biased. Mr. Thomas Preston Brooke manufactures a type of motor in which he aims to eliminate the gyroscopic effect. His motor is a machine combining two rotary motors going in opposite directions. If the gyroscopic effect is so undesirable, why is it that Mr. Brooke's motor is not used more generally in this country ? 1 have never seen it fitted to a single aeroplane, nor does it hold a record of any kind in this country. Of course, it may be a very excellent motor for all that, but the necessary complication of connecting two rotary motors together so as to revolve in opposite directions is, in my opinion, a step which is in the wrong direction and entirely unnecessary. Of course, that is only my personal view, and I am not interested in the matter in any way financially. I have several times taken the position of a fharp critic simply because I am vitally interested in the development of the aeroplane, and wish to render whatever assistance I can as a practical aviator and aeronautical engineer. Mr. Brooke, in his letter, seems to think that practically all of the aeroplane accidents may be attributed to the dreaded gyroscopic force so-called. Personally, 1 am of the opinion that there has not been a single accident caused by Ike gyroscopic action of the motor. I don't mean to say that this action is absent, but I do say that, as a prac tical aviator, I never noticed its effect, and that I never had to correct my controls in the manipulation of my aeroplane to counter balance this terrible (?) force. The apparatus Mr. Brooke used to demonstrate the deadly effect of this gyroscopic force I had occasion to examine while flying at the Chicago meet. Briefly, it consisted of a series-wound motor with a heavy fly-wheel on either end of the shaft ; and a large portion of the weight of these fly-wheels was located in the periphery. Now anyone who is acquainted with the series-wound motor knows that it has no speed regulation. The more current you put into it the faster it will go. In demonstrating the gyroscopic effect Mr. Brooke ran the motor up to a speed of perhaps three or four thousand revolutions, and then endeavoured to change the plane of rotation of the revolving fly-wheels quickly. Of course an enormous gyroscopic effect was produced. But this experiment was very far from what actually takes place in an aeroplane. Under flying conditions the speed of rotation of the engine is never more than twelve or fourteen hundred revolutions per minute, which is about one-third of the speed at which he revolved his fly-wheels. Further more, the weight of a rotary engine is not by any means all located in the periphery. The heaviest parts are located near the centre of rotation where the gyroscopic force is much less. Then again n sane aviator endeavours to change the plane of rotation of his mot.ir suddenly. I claim that if Mr. Brooke performed an experiment which was more nearly actual practice, he would not rind that the gyroscopic effect is so pronounced as he thinks it is. Leaving theory aside, which at the best is often unsatisfactory, and turning to practice, let me say that, a« an aviator who has flown hundreds of miles in a Bleriot monoplane fitted with a rotary Gnome motor of 70-h.p., I have never had to allow for this gyroscopic effect. This is in spite of the fact that one of my stock feats in exhibition flying was to vol plane" at a sharp angle from a height of one or two thousand feet, and when twenty or thirty feet from the ground change the plane of rotation of my engine, and shoot into the air again. And never once did I notice any gyroscopic effect. While Mr. Brooke (meet of 1911) was in Chicago telling all of us boys how dangerous was the gyroscopic effect, we were racing around the short course at Grant Park, banking our machines at 60', and turning corners sharply with absolutely no difficulty and with no fatality. There are enough impediments in the way of the aeroplane without putting in imaginary ones. And he who does not think the gyroscopic effect is largely imaginary had better ask one of your prominent aviators who uses the rotary engine in order to have my opinion substantiated. Mass., U.S.A., Sept. 26th, 1912. EARI.E L. OVINGTON. Gyroscopic Action. [1645] I was much interested to see in a note of yours, following a letter from Mr. R. M. Pearson on the above subject in your issue of September 21st last, that gyroscopic force appears to set up " a bad tremor through the machine when turning." It appears to me that the explanation of this lies in the gyroscopic torque induced by the two-bladed propeller, as suggested in my letter to FLIGHT of June 29th last. If this is the ca^e, it would be felt on any single- propeller machine, whether fitted with a rotary engine or not. It would be interesting to know if this is the case. With regard to the general question of gyroscopic force, it is a pity that so much mystery seems to be made about it in some quarters. For instance, in FLIGHT for August 24th last, Mr. T. P. Brooke speaks of the " erratic action of gyroscopic force." From this anyone would suppose that it followed no law and that prediction was impossible. Instead of this, the laws are comparatively simple, and bear a close and analogous relation to those governing centrifugal force. For if we consider a mass M moving in a circular path with linear velocity V and angular velocity m (=. V •+• radius), the centri fugal force is equal to MV x <o. The case of gyroscopic torque is equally simple. If we consider a body of moment of inertia I revolving at angular velocity fl whose axis of revolution is turned in space at angular velocity w, the gyroscopic torque is equal to In x iu. Centrifugal force is the product of a linear momentum, and the angular velocity with which the direction of this linear momentum is changed in space. Similarly, gyroscopic torque is the product of an angular momentum, and the angular velocity with which the direction of the axis of the angular momentum is turned in space. Both are a consequence of Newton's first law of motion. As you state in your note referred to above, the difficulty in the case of the aeroplane lies in finding the angular velocity with which the direction of the spinning axis is turned in space. One would expect the worst case to be that in which a sudden wind eddy or gust throws up or down the nose of the machine, so generating a sudden torque tending to turn the machine round a vertical axis. I note that Mr. Brooke slates that "a very sudden lift or drop in the front end" induces a force which tends to pitch the machine violently downward. It would be interesting to know by what reasoning or experiment he arrives at this conclu sion, as gyroscopic torque always appears round an axis at right angles to that of the disturbing torque. Rugby. R. C. CLINKER. The Death of Mr. R. C. Fenwick and a Proposed Memorial. [1646] It has recently come to my notice that at the moment when Fenwick's accident occurred, a passenger in another aeroplane then in the air was thrown violently from his seat against part of the machine, and cut his face badly, while the pilot of that aero- 925
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