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Aviation History
1929
1929 - 0194.PDF
JANUARY 31, 1929 consumption of 14 -3 gallons per hour. Obviously, while the machine is fully loaded the consumption will be greater than this and towards the end, when something like 7,000 lbs. weight has been lost by the consumption of nearly all the fuel, the hourly petrol consumption will be smaller. The photographs of the Fairey monoplane which we publish this week disclose certain very obvious features in the design. Thus, the wing span, which is given as 82 ft., is obviously very large in proportion to the cross section of the fuselage. The mean chord is given as 11 ft., which would give a total wing area of 902 square ft. This is a very large area for a mono- plane and probably indicates that although the power loading at the start may be fairly high, the wing loading most likely is not unduly high. It is, of course, a well-known fact that one may with reasonable safety employ either very high power loading or very high wing loading. It is when an attempt is made to make both the wing loading and the power loading high that difficulties in taking off are experi- enced. It seems likely that in this respect the Fairey mono- plane should be in the fortunate position of being able to take off relatively easily with its full load on board, especially as the span loading and induced drag must be fairly low. By placing the fuel tanks in the wing several desirable 378 propeller horse-power at 130 m.p.h. or at 75 per cent, efficiency, to a brake horse-power of about 500. In point of fact, there is good reason to believe that the drag of the Fairey monoplane is lower than that, and it is quite possible that its actual top speed is nearer 140 m.p.h. However, it is not top speed that interests us so much as cruising speed. The Everling " distance figure " expresses ratio of lift to drag, multiplied by propeller efficiency. Usually, however, the optimum value of the " distance figure " cannot be found, as this requires a knowledge of the characteristic curves of the machine and the power developed by the engine at the best cruising speed. Consequently, the " distance figure " given in FLIGHT'S descriptions of air- craft is nearly always that corresponding to top speed, and is thus often considerably lower than the optimum value. It seems likely that in the case of the Fairey monoplane the distance figure " corresponding to best angle is at least 7, and in all probability it is more than that. But even assuming it to be 7 this would give a value of L/D of between 9 andjlO, which is probably not overestimated. All these speculations, and they are admittedly little more than guesswork, appear to indicate that the Fairey long-distance monoplane should have a very good chance m m m m An important item: The Napier " Lion " is ex- tremely neatly cowled, as this view of the " nose " shows. Note also how windscreen mer- ges into the top surface. ["FLIGHT" Photograph features have been attained. For instance, by this means it has been possible to keep the fuselage of quite small cross sectional area. The fuselage is, in fact, little more than a substantial beam carrying the tail surfaces and engine, and housing in the centre the crew of the machine. Thus, the Fairey monoplane must be regarded as having gone a con- siderable way towards the old Junkers ideal of the flying wing, i.e., the machine in which crew, passengers, etc., are housed entirely in the wing, the fuselage and all other projections being suppressed. It is not claimed, of course, that there is no parasite drag on this machine, but it must be a much smaller percentage of the total than is found in the great majority of machines. What the minimum drag is cannot well be estimated with any degree of accuracy, unless one is in possession of a considerable number of data. In view of the very small proportion of fuselage to wing it seems quite possible that the Everling " high speed figure " is at least as high as, if not higher than, that of any machine of which we have data. Thus, for the De Havilland type " Tiger Moth," the Everling " high speed figure " is 26, which is a value well above the average. In all probability the figure iox the Fairey monoplane is higher than that, but even if this figure is assumed we arrive, if a propeller efficiency of 75 per cent, at top speed is assumed, at a minimum drag coefficient of 0 -014 in British " absolute " units. That this figure is not by any means an impossible one will be realised when it is pointed out that it corresponds to a power requirement of of beating the existing world's straight-line distance record. This, it may be remembered, is held by the Italian aviators Ferrarin and del Prete, who on July 3, 4 and 5 flew, in a Savoia-Marchetti S.64 monoplane with Fiat A.22 engine, from Rome to Touros in Brazil, a distance of 7,188-26 km. (about 4,460 miles). The same two aviators had, about a month previously, established a world's record for distance over a closed circuit by covering no less than 7,666-6 km. (about 4,750 miles). The duration record of 65 hours 25 mins. is held by two German pilots, Ristics and Zimmermann, on a Junkers W.33 monoplane, with280-h.p. Junkers L.V. engine. Although the two records have much in common, there are essential differences. For the duration record speed is of very small importance; for the distance record, however, speed is obviously an important factor, and here really " clean " aerodynamic design is a tremendous advantage. We have no actual knowledge of the data of the Fairey, but it appears to us that if it is indeed able to beat the duration record it should be even more favourably placed as regards beating the distance record by a handsome margin. We have referred to the fact that placing the petrol tanks in the wing has several advantages. The reduction of the fuselage area has already been dealt with. The photographs of the machine indicate that the petrol tanks extend a con- siderable distance outboard. As at least half of the total loaded weight is constituted by the petrol, this placing of 80
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