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Aviation History
1923
1923 - 0078.PDF
the variable pitch propeller, on which much experiment is now taking place. Given control on the pitch very much improved results could be obtained and greater loads lifted for a given power. An alternative, and seemingly easier solution, would be the provision of a two-speed gear on the engine, the gear ratios being arranged so as to give maximum engine revolutions under two conditions—(1) at hump speed for the machine, (2) at maximum or cruising speed, according to which was desired. This is a course I have been advocating for some time, and I would take this opportunity to impress upon engine designers the urgent need of this feature for seaplane work. It would seem that an engine fitted with an epicyclic gear would be particularly adaptable for this purpose, as it would avoid the necessity of a clutch or gear-changing mechanism. The alternative gear could be engaged by means of a brake-band exactly in the manner of a Ford car, and the only necessary operation by the pilot would be to hold in a low gear until the machine had passed the hump speed. Comparison with the Aeroplane Mr Fairey showed a set of curves of percentage structure weight of a number of existing machines. The curves, he continued, appear to illustrate the writer's suggestion that the average of advantage lies with the float type for small machines and the boat for big ones, and further that large flying boats should be superior in performance to large aeroplanes, while large float types show enough promise to justify experiment with them. The most striking curve is that of the flying boat. This, starting at a very great disadvantage to the aeroplane, over- hauls it in medium sizes and passes it in large sizes, and in the biggest machine yet built shows even further improvement with no sign of the curve turning up. In other words, the limit for big seaplanes is far from reached, whereas that of aeroplanes, while not necessarily in view, will obviously be met first. Moreover, it would appear that the bigger aero- planes get the greater will be the difficulty in this respect. (One large German giant machine has no less than eighteen wheels for its support.) The difficulties in handling large aeroplanes are tremendous. They need unduly large aero- dromes, which must have a hard surface, and most flat country suitable for aerodromes is of a soft nature, whereas the large flying boat has an unlimited " aerodrome." It does hot need the rate of climb for safety in taking off that an aeroplane does, and does not present the same difficulties in handling. On the theoretical basis alone there are many reasons why the overall size of both aeroplanes and seaplanes is strictly limited, but the practical results obtained appear to indicate that the limiting size is very much larger than would be anticipated from theoretical conditions. Also it must be remembered that in none of these curves are safety factors taken into account, but since many types are taken this would average out to a certain extent, and since the larger machine by its steadier flight, and the fact that there is no FEBRUARY 8, 1923 need to design it to the strength of the fighting scout, has a natural advantage in this respect, it is only fair that this should be taken account of in considering the average effect. In short the curves would appear to show (subject to any criticisms that may be made of the basis on which they are plotted) the outstanding advantages that the seaplane T'- possesses over the aeroplane that its proper place is in large sizes ; it is not limited by the size of aerodromes or the v. necessity of clearing obstacles after leaving the ground ; it cannot be bogged as large aeroplanes will be, and is used on » anything but the hardest aerodromes. While inferior to the aeroplane in small sizes, the seaplane would appear to have overwhelming advantages in large sizes if these are properly developed. One other theoretical consideration should be mentioned in view of the fact that the seaplane, unless for use on inland rivers, is not limited by the size of the aerodrome. It would appear at first sight that some advantage could be taken of this fact with a view to increasing the wing loading with corresponding effect on the landing speed. Unfortunately for small machines this is not the case. Landing speeds of 45 knots ; or thereabouts appear to be the practical limit, partly because a running landing is not always possible and the machine must have a landing speed at least low enough to make a semi- stalled pancake landing, but also because the high wing loadings would result in raising, the power required curve at low speeds owing to the fact that proportionately less of the total weight would be taken on the wings and the old difficulty of the hump speed would be exaggerated. In this respect, **.. however, it is suggested it is not that the landing speed of the seaplane is too low, but that of the aeroplane much too high, and that for equivalent landing speeds the seaplane is in » reality much the safer of the two. In conclusion I had hoped to be able to deal with some commercial aspects of the seaplane, particularly in regard to its future possibilities, but I have found that even to deal in ,. outline with a few outstanding practical and theoretical problems has already absorbed the available time, and pro- vided more subjects than can be usefully dealt with in dis- cussion. I can only hope that this matter will be dealt with at some future Conference, or possibly in discussion, for it is important that the commercial possibilities of the seaplane should be appreciated by the general public in addition to designers and others immediately concerned with the problem. There is one other important aspect of the seaplane question to which I would like to refer. There is an idea growing common that British designs lead the world. There is enough truth in such a statement in relation to the structure and performance of British machines to make it dangerous to future progress. Design and construction of experimental machines is only a part of the problem. Principles can be established by research, and the arrangement and construction of machines more or less perfected in a few examples of machines, but before seaplanes or aeroplanes become practical 1 -.:" • •• '.* -•'•: '' • -• • ' "—' •'•'.' Besson Triplane N.T. 2.BMacchi .. :7 Farman 450 h.p. .. N.C. 4 ....... • Supermarine Schnei- der, Cup Winner(1922) Nieuport DornierSavoiaS.16.. Supermarine Seagull Amphibian Viking IVF.3 P.5 Short Cromarty Felixstowe Fury .. Atalanta N.4 APPENDIX Classified List of Existing Modern Seaplanes Flying Boats Single-Step Type Gross Wt. lbs. 1,910 3,1693,540 6,380 28,000 Useful Load. lbs. 590 848 1,100 2,200 12,900 Structural Weight.o lbs. 955 1,4701,560 2,600 9,800 Flying Boats Two-Step Type 3,2743,850 4,4004,620 5,680 5,700 5,67511,900 12,055 19,700 27,700 32,000 800 1,325 L4401,760 2,000 1,960 1,8724,250 4,700 7,412 11,500 11,700 1,1101,735 1,8001,850 2.180 2,280 2,1214,750 4,330 7,310 9,200 10,300 0/ I /o50 46 44 40 35 34 45 41 40 38.4 40 37.439.8 35.8 37.1 33.2 32.2 Wt./ H.P. lbs. 14.5 14.9514.2 14.2 16.7 6.9 19 23.816 12.2 16.2 12 16.5 16.75 18.75 15.4 12.3 Wt./ sq.ft.A. lbs. 5.9 7.1 7.3 7.2 11.7 7.6 8.8 8.1 9.4 7.3 8.77 8.75 11.1 Twin P.V.2 . .„ Bis 184 ShortRicciR.l.C. Twin P.V.SaFairey Pintail III (Amphibian) Caudron Float Seaplanes Float—Single-Step Type 1,5901,702 4,50010,600 Float 503491 1,0204,000 78/911 2,0804,230 Seaplanes 49.353.5 46.340 ••'loat—Double-Step Type 2,518 4,700 6,750 Float 546 1,350 2,000 1,217 1,950 3,200 Seaplanes 48.3 41.5 47.5 15.917 18 15 12.6 10 17.4 • •. 9.59.5 6.5 8.2 8.1 10.7 7.2 Twin Float Type, intermediate between the Single-Step and the Double-Step Avro Polar Expedi-tion P.V.9 Avro ViperL.V.G. W.II Junkers (Duralumin construction) L.V. W.IL.F.G. V.20 Short N.2b Fairey III.D ,, Atlantic, Mark II 1,5891,965 2,5672,650 3,120 3,4603,475 4,938 5,050 7,150 589 561 604 650 1,105 810 1,275 1.586 1,650 3,100 Types 687 960 1,1701,220 1,100 1,3701,320 1,852 2,020 2,600 43.249 45.546 35.4 39.538 37.5 40 36.3 18.713.1 12.2 14.3 14 20 9.238.65 7.92 7.05 10 10 78
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