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Aviation History
1917
1917 - 0473.PDF
MAY 17, 1917. THE I/LIGHT 1 AEROPLANE.••TOTALLY ENCLOSED Concluded from page 448.) Another arrangement suitable for a small machine is thatHAVING briefly reviewed, in preceding issues of " FLIGHT,"the more important of the " enclosed " aeroplanes that have been constructed up to the present, a short r&sutne of theadvantages and disadvantages of the different types may be helpful in forming an opinion of the lines along which progressis likely to be made in the future with this type of machine. Practically speaking, the tractor type of enclosed aero-plane, whether monoplane or biplane, suffers from one •common fault, i.e., the view in a forward direction is badlyrestricted owing to the presence of the engine. In those of the machines reviewed in which the engine was mountedhigh so as to improve the view to a certain extent, it was generally concluded that the centre of thrust was somewhattoo high, thus introducing an aerodynamical disadvantage tending to minimise or even nullify the practical advantageof this arrangement. In the Curtiss Autoplane an attempt has been made to overcome this difficulty by placing the•engine in front but very low down, where the pilot can easily look over and beyond, and by employing shaft drive to apropeller placed at the rear end as near as it is possible to judge without knowing results of wind tunnel tests, on orvery close to the centre of resistance. The only " pusher " of the enclosed type, properly speaking,was the Bleriot Aerocar, built for Mons. Deutsch de la Meurthe. In this both engine and air screw were placed at the rear, or,in other words, well out of sight as regards the pilot's view, but*this machine, it can be easily seen in the light of modernknowledge, suffered from other drawbacks such as excessive head resistance formed by the large flat front of the cabinand by the numerous outriggers carrying front elevator and tail planes. Also the machine was probably too heavily loaded,being of the monoplane type and designed to carry five persons. originated by the Curtiss firm with their Autoplane. Fromthe point of view of visibility this arrangement is excellent, and with the engine in front and a long and necessarily fairlysturdy shaft running through the whole length of the cabin, it should be a very safe one in case of accidents. Although theCurtiss firm are fitting triplane wings to their machine, it does not necessarily follow that this is the only possible arrange-ment, although the triplane lends itself very well to it. It is conceivable that biplane, or even monoplane, wings could, beemployed. Until the Curtiss Autoplane has flown and one knows something about its behaviour in the air, it is difficultto form an opinion of the merits, aerodynamically speaking, of this arrangement, which is certainly very promising in otherrespects. As we have already pointed out, the Bleriot Aerocar is,so far, the only representative of the true " pusher " type of machine having both engine and air screw placed at the rear.A development of this type,, which obviously suggests itself, is to employ biplane wings as in the ordinary " pusher "biplane, and to make the nacelle totally enclosed, the tail planes being carried on an outrigger in the usual way. Bymaking the nacelle rounded in front, its sides gradually flattening out towards the rear, where it would terminatein a .vertical knife edge of nearly the sa*me length as the gap between the planes, the added side area in front should notmake the machine spirally unstable, as the flat sides towards the rear would counteract the rounded side area of the nose.By fitting windows in the naK, sides, roof and floor of the cabin, a very good view coula be obtained in all directions.Here again the e«gine would for preference be of the water- cooled type, as the cooling of an air-cooled motor at the rear _ the large machines that have been or could easily be might hi attended with some difficulty in view of the shapemade " totally enclosed," we have two main types, one ^presented by the Sikorsky and Handley-Page biplanes, andthe other by the Curtiss America type flying boat. Both the latter types are at a distinct advantage as regards" visibility," owing to the fact that they have two engines mounted out on the wings, where they do not greatly obstructthe view. This arrangement is not, however, economical except for large machines, and the inherent advantages of itwill therefore scarcely be available for the small single seater '--•..-• or two-seater limousine of the future. V" With regard to future development. It is always dangerous;.; . to venture to prophesy, more so, probably, in reference to matters aeronautical than in any other branch of science, butwith due regard to such improvements as appear likely to be made in the way of engine and aeroplane efficiency, it may bepossible to eliminate the types that appear least promising, -V, and to indicate lines along which progress would appear to. be most easily made. It has already been stated that the ordinary tractor typewith direct drive and having engine and air screw placed in front suffers from serious drawbacks owing to the obstruction -^ formed by the comparatively large bulk of the engine directly in front of the occupants. It is possible that by somewhatre-designing this arrangement a serviceable machine of this type may be produced. For instance, take an enclosed*;..;: biplane. If the engine is placed well down in the body and the seats of the occupants are situated fairly high in thebody, say, for the sake of argument, so high that their heads are nearly touching the roof of the c'abin, the resultant centreof gravity, especially if the tanks are also placed high, should not be so low as to render the machine difficult to handle.The Morane-Saulnier parasol monoplanes have already demonstrated that it is no serious drawback to have even avery low centre of gravity. The air screw could, by employing a suitable form of transmission—and this is a subject which,to our way of thinking, should be given the very greatest consideration since, up to the present, little has been done inthis respect—be so placed as to coincide with the centre of resistance. The obstruction to visibility caused by a re-volving propeller is comparatively unimportant, even when the •engine is throttled down, as it would be when the machinewas landing. Incidentally this arrangement, with the engine in front and low down, and the passengers to the rear of andabove the engine, would be one of the safest imaginable in the case of a bad landing. A small, and by small we meana single-seater or a two-seater, monoplane or biplane of this type would appear to be quite a reasonable proposition.The form of engine best suited for this purpose would probably "be a vertical or Vee water-cooled, as this could be more easilyhidden away in the lower part of the body than could any air-cooled engine, whether of the radial, rotary, or Vee type. of the rear of the nacelle. Unless objection is taken to havingan engine behind one in the case of an accident, this arrange- ment would appear quite feasible, and, in practice, the"pusher" type without the totally enclosed nacelle does not seem to have proved so dangerous from this source asmost people were inclined to'imagine. Between the three types indicated above there should be ample scope for varietyand originality, and developments are likely to be made with all of these. We now come to deal with the large enclosed machine.Here the feature of enclosing will come as a matter of course, since this type of aeroplane will be used for flights of longduration, and already lends itself extrcmefy well to closing in, on account of the fact that the engines are placed on thewings. There appears to be good reason to believe that, as the machines grow in size and carrying capacity, multiplanes. will prove of advantage, and it will, in all probability, be along these lines that the large machines of the Handley-Pageand Sikorsky type will develop. In the case of the flying boat it is less simple to fit multiplanes, as the position ofthe lower wing is limited in a downward direction, and arly addition of wings will result "in a low centre of gravity. Forcertain classes of work there does not appear to be any objection to providing the Handley-Page and Sikorsky type with floatsso as to convert them into seaplanes, although the time is scarcely ripe to venture an opinion of the relative merits foropen sea work of the seaplane and flying boat types. It would thus appear probable that the transcontinentaland transoceanic mail carrying aeroplanes of the future will be of the multi-engined and multiplane type, since theemployment of several engines tends to make for greater reliability and more than two pairs of superimposed wingsare structurally economical, especially for very large machines. Already existing machines form a .very good basis to workupon, and the long-distance aeroplane is held by many authorities to be a mechanical possibility at the present time. That the enclosed aeroplane will have to come cannot bedoubted, not only because in the future flights of much longer duration than are common at present will be made, but alsobecause for comfortable flying—apart, of course, from racing and other flying sports, for which the open type will still beemployed in order to get better performance—it is not very enjoyable to sit with one's nose in a draught of anything from70 to 100 m.p.h. Manufacturers are at present too busily engaged on meeting the more immediate demands of theflying services for war purposes, but when peace shall again reign there will be enormous development in sporting andcommercial aeronautics, and the manufacturer who is far- sighted enough to realise its possibilities will lose no timein getting his drawing office staff to work on the development of the peace time machine. 473 F
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