January, 1941 AIRCRAFT ENGINEERING but it is probably capable of being overcome. The important point here is that it will not do merely to add a tricycle undercarriage as Aircraft Engineering an afterthought to a normal aeroplane. The machine must be designed from the beginning with the undercarriage in mind and Devote d to th e Science an d Practice of Aero must incorporate any special features required owing to the unde nautic s and to Allied and Subsidiary sirable features we have mentioned. Resort will probably have to be made to special flaps to come right down and act as true air Branche s of th e Engineerin g Industry brakes during taxying. Wheel brakes will also have to be carefully designed to be thoroughly efficient and powerful—the fact that the Editor: Lieut.-Col. W. Lockwood Marsh, F.R.Ae.S., M.S.A.E., F.I.Ae.S. danger of nosing over should be eliminated being borne in mind. A great advantage that the tricycle undercarriage brings in landing, Vol. XIII , No. 143 January, 1941 which we have not mentioned, is that the pilot's view forward will THE TRICYCLE UNDERCARRIAGE remain the same as in level flight and he will not be subjected to that trying, and dangerous, sudden loss of sight of the ground, ITH typical Teutonic thoroughness the article which we owing to blanketing by the wings, which is the undesirable concomi publish in translation form from Luftwissen this month, W tant of the present-day flap. contains as complete data as is probably possible on the evolution of the tricycle undercarriage, with particular reference Dangerous as it is to prophecy, we venture to predict that in a to its development in the United States. Great credit is due to short space of time the tricycle undercarriage may well be universal MR. WEICK for his vision in foreseeing the advantages of this old —or nearly so. The Douglas firm have already introduced it into a but long-disused form of undercarriage. It is true that he was in bomber and the Bell and Lockheed companies are showing the his inception chiefly concerned with the improvement of landing possibilities in fighters—though in each case of a rather specialized conditions for the inexperienced amateur pilot and can scarcely type. In view of the conditions imposed by modern warfare, have envisaged the potentialities—and how the small ball he necessitating the use of emergency and temporary landing grounds started would increase in size and the as prepared aerodromes arc rendered un distance to which it would roll. inhabitable or when the army is on the move, the improved facilities offered British Delay arc likely to become of paramount im As so often before, in aeronautics and in portance. other matters, we in England displayed WELDING LIGHT ALLOYS our usual British caution and sat back and watched before entering the field our We are greatly indebted to the Institute selves. Indeed, even yet the tricycle of Welding for permission to reproduce undercarriage has scarcely begun to from its Transactions the important report appear on British machines, and has not of investigations carried out on its behalf been adopted by any of the principle by MESSRS. FIELD AND SUTTON (whose designers. The reason for this is, actually, name is well known to readers of AIRCRAFT fairly simple. In these days of retractable ENGINEERING) into the spot welding of landing gear the disposal of the nose light alloys. The subject is of such wheel is by no means an easy problem, peculiar interest at the present time to the and all the machines at present in service aeronautical industry that we felt their use, and even those now beginning to attention should be drawn to this most come into production, must have been valuable report in these columns. designed before the tricycle was thought of ; and it is hardly a On the whole, the results confirm the view already held in the device which can be incorporated as a last-minute modification best-informed quarters that, at the present time, welding as a method in a new type of which the main features arc already fixed. The of joining light alloy components is to some extent open to suspicion, problem of " stowage " is already acute, and this is a further and and should only be used with caution. In the present state of by no means welcome complication for the designer. However, knowledge, and with existing practice, it would not seem safe to some of the new types of which early deliveries are promised from rely on it in parts which arc likely to be highly stressed in service. America incorporate this feature to serve as examples, though Though much can be done by correct subsequent heat-treatment we do not doubt that most British designers are already alive to its to overcome the deleterious effects, the application of welding advantages and at any rate experimenting with the various methods seriously, as might be expected, increases the liability of duralumin of installation. to corrosion—for which reason there is, of course, less objection to its employment with duralumin when coated with aluminium, a There is by now no doubt that the presence of a nose wheel im material commonly known by the trade name of " Alcald." proves the take-off characteristics of an aeroplane. The machine starts from rest in approximately flying position and the time and, There are several, to us, unexpected points that come out. It perhaps in many instances even more important, the distance is difficult to see quite why the results are so unsatisfactory when occupied in running along the ground to get the tail up is saved. electric welding is used for joining two sheets of dissimilar thickness ; At the end of the take-off run the machine is, again, in flying attitude particularly since the joining of thin sheets to extruded sections and therefore flies off naturally into the air ; in contrast to its having showed up quite as favourably as joints so made between two to be " yanked " off as in the normal—we almost wrote " old- sheets of equal thickness. Whether there is any useful lesson to be fashioned "—manner. This not only effects a further saving in drawn from the fact that higher amperages were found necessary time and length of run but also considerably reduces the danger of a we do not know. stalled zoom take-off before the load is truly air-borne. Another point of considerable interest is the strikingly good results obtained with spot welds on M.G. 7 type alloy ; the Ps/T ratio Use in Landing (failing load divided by the thickness) being considerably higher In landing, on the other hand, the tricycle undercarriage, at any than that of welds in either Alelad or duralumin. This is a point in favour of this material which, no doubt, will not be lost sight of by rate as at present used, tends perhaps to be more of a liability. It is true that it makes the actual " putting down " of the machine more aeroplane designers. The wide variation in the nature of the or less automatic, and so is a great asset in blind-landing conditions results obtained from welds made with different machines, and even and eases matters for the inexperienced pilot. But it would seem with the same machine and a given setting, obviously require further that inevitably, other conditions being equal, the landing run will elucidation and we hope that the sub-committee concerned is putting these in hand. A clear knowledge of the conditions necessary be longer, owing to the lack of change in the attitude of the machine after touching down, and the approach will be made at a flatter for the production of spot welds of even quality and with predictable gliding angle, necessitating a larger and unencumbered aerodrome. shear strengths is obviously necessary before spot welding of light This appears at first sight to cancel out the improvement in take-off, alloys becomes common practice.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Jan 1, 1941
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