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Aviation History
1938
1938 - 0301.PDF
FEBRUARY 3, 1938. FLIGHT. T03 TALKING-OVER the TRICYCLE Three-wheeled Undercarriages Debated at Length by R.Ae.S. Members : Some Valuable Opinions THE tricycle undercarriage held the stage almost to theexclusion of other subjects at last Thursday's re-sumed discussion of the papers by Mr. H. F. Vessey and Sqn. Ldr. H. P. Fraser, read before the Royal Aeronautical Society on November 18 and December 2 re spectively. There could be no doubt that the general feel- ing at the meeting was overwhelmingly in favour of the tricycle undercarriage. The opposition, if such it could be called, was confined to one speaker, Capt. F. S. Barnwell, whose views will be found reported in their proper place in the discussion. MK. F. HANDLEY PAGE was in the chair and asked Mr. D. L. Hollis Williams to open the discussion. ; MR. HOLLIS WILLIAMS pointed out that, by a coincidence, papers on high wing loadings and tricycle undercarriages had been read and discussed very close together in point of time. It was, however, no coincidence in reality that the two subjects should be taken together. There was a close connection between them. The modern tendency to high wing loadings was curbed by the problems connected with making contact with the ground. The fitting of tricycle undercarriages made it possible to increase the wing loading by reducing the skill required in landing a machine. He defined the meaning of the expression " tricycle undercarriage " as any undercarriage, irrespective of the actual number of wheels used, which re- duced the angle of incidence. The advantages of the tricycle undercarriage were: Good view, directional stability on the ground, reduced swing if one engine stopped, less skill required for landing, and the possi- bility of landing with a considerable vertical velocity instead of zero vertical velocity. The disadvantages were an increase in structure weight and an inconvenient installation, as the nose wheel would have to retract into part of the fuselage which was usually required for a turret or a bomber's window. He put to the meeting the proposition that the need for three- point landings was fundamentally wrong and should be abolished. , ..•".• / . .-..•;- ; - Paying For It CAPT. F. S. BARNWELL pointed out that the great advance in performance had been due to an increase in wing loading. The increased performance had made it necessary to use variable-pitch airscrews, and the increased loading had demanded flaps for reducing the landing speed. Neither of these things improved performance by itself but was necessary. He thought they ought to make very certain that the tricycle undercarriage was necessary. If the operators wanted tricycle undercarriages designers would certainly provide them, but it should be remembered that the front wheel would add about 2 per cent, of the gross weight. As the payload was usually about 20 per cent, of the gross weight, this meant that the front wheeJ would reduce the payload by 10 per cent, or so. By fitting a tricycle undercarriage the advantage of the use of the wings as an air brake was lost. Much had been made of the increased braking effect that could be obtained from a tncycle undercarriage. What was chiefly wanted was the power to manoeuvre on the ground, and on large commercial machines it could quite well be arranged that the differential action of the wheel brakes was improved. To stop any ten- dency to swinging during taxying, the tail wheel could quite easily be so designed that it was locked central when that was desired. ri tlAJi F' M' GREEN thought too much had been made of the j1^ of landing aircraft. If past civil aviation history were wh^Tt1' hg wondered how many accidents one would find a f +K b^Cn causecl during landing. Pie admitted that in f. °,g ^e tricycle undercarriage was an advantage. If the it « wheel, were fitted one would have to make very sure that a coinr.1" fai.*e<* in any circumstances. He thought that even Wheel iVe!y triflin8 matter like a burst tyre on the front tyrg wouId be just as serious, if not more so, as a burst main MR. L. E. COWEY, by way of explaining the advantages of his particular type of tricycle landing gear in which the third wheel is behind the main wheels, read lengthy extracts from an article which appeared in Flight of June 18, 1936. He added that since that time his firm (British Landing Gears, Ltd.) bad made a considerable number of experiments. As to the relative merits of the single-wheel-in-lront or single-wheel-behind type of tricycle undercarriage, Mr. Cowey said that one advantage of the single-wheel-behind type was that the wheelbase was longer, so that the machine should be more stable on the ground. Any tendency to ground-looping which might be present owing to the position of the two main wheels fairly far; ahead of the e.g. could be cured by stiffening the castering action of the rear wheel. With the single wheel behind, the braking action was better because the two front wheels were ahead of the e.g., and when the brakes were applied extra weight was thrown on to these wheels. Pie also referred to! the difficulties of retracting a front wheel, particularly in a- single-engined aeroplane. • MR. B. SHENSTONE wondered if the tricycle arrangement with single wheel in front did not cause the machine to swing into wind during a glide landing. For use in the Fleet Air Arm he thought the front wheel might be a disadvantage in that; it would probably cause the machine to run sideways across the landing deck if the deck was sloping through rolling of the carrier. I MR. R. L. ALSTON pointed out that Mr. Shenstone was wrong in thinking the tricycle undercarriage would cause a swing into wind. On the contrary, the tricycle undercarriage was stable on the ground, and if the machine was landed with side-drift on, the tendency would be for it to swing into the direction in which it was drifting. It was different on board ship, where the machine would, as Mr. Shenstone had pointed out, have a tendency to run off the deck. While it was true that skilled pilots managed to land the present-day aircraft quite satisfactorily, it was in bad weather conditions that the tricycle undercarriage was of the greatest advantage, and then even skilled pilots might be glad of it. In case of war it was to be assumed that pilots would not be so highly skilled as they were in peace time, and then the tricycle undercarriage would be a very considerable help. Misapplication Mr. Alston was sorry that all the new devices which had beea introduced seemed to have been used for extending the speed range at the top of the scale. He hoped the tricycle would not be used in the same way, but that, on the contrary, it would be used to improve matters at the lower end of the speed scale. He did not quite agree with Capt. Barnwell that the increase of 2 per cent, in weight was serious. The tricvele type of undercarriage would enable heavier loads to be taken (iff, and this would more than pay for the 2 per cent. lost. He concluded by regretting that we had no machines in this country of the sort comparable with the Hammond Y tvpe. Perhaps our constructors thought the subject one of no*im- portance, but he did hope that the Royal Aeronautical Society
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