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Aviation History
1934
1934 - 1472.PDF
SUPPLEMENT TO FLIGHT I28of NOVEMBER 29, 1934 THE AIRCRAFT ENGINEER FRENCH BOAT CONSTRUCTION : Internal struc-ture of LeO H.24 hull. or vice versa. It does not appear to matter which. But in this hull both are widely spaced and the shell plating seems to be uncommonly unsupported. The twin-tailed Levasseur seaplane is also odd, and can have only military significance. The snub-ended fuselage has a tubular framework covered with ribbed metal sheeting. The two attenuated floats are structurally ordinary but appear to be very narrow-waisted and may not be suitable for open sea work. The upper works of the Junkers Ju. 52.3-m. has been discussed above, but its floats may be appropriately men- tioned here. In England our only experience of the very- large twin-float seaplane has not encouraged us in its development. Both the French and Germans have gone further with this type, but their tideless seas, the Medi- terranean and the Baltic, may be more encouraging than our wilder waters. The Junkers floats are a " hefty " piece of work, straightforward and solid. The only other marine flavour was given by the stainless steel-welded floats mentioned at the beginning of this article. It will be very interesting to hear how their very thin plating stands oip to the buffeting of rough water. FIGURES OF MERIT By R. RODGER Continued from page 76) 12.-Typical Data In Fig. 2 an attempt has been made to compile data relating to figures of merit for a number of the more up-to- date British. American, and Continental civil aeroplanes. The writer considers the use of the word " attempt " to be advisable because the attainment of anything approaching correlative results is almost a heartbreaking task. The utter disregard for consistency in the presentation of the basic data shown by various authorities is truly remarkable. Sometimes normal power output is quoted, sometimes the maximum. Sometimes the gross weight quoted is the maximum permitted by the C. of A., whilst the performance refers to the aeroplane flying light, and exactly how light is not always mentioned. Tare weight sometimes includes cabin furniture, etc., whilst for another machine these items may be referred to as part of the disposable load. Even the main plane area seems to be a doubtful quantity as one instance arises in which the wing loading is based on main plane area including ailerons and body. Under these circumstances it is absolutely necessary to accompany Fig. 2 by a commentary to prevent, as far as possible, misapprehension of the results on the part of the reader. In the table alternative values are often quoted and in such cases there is inconsistency in the basic data, the reader being referred to the commentary for the nature of the adjustments made. " ' 13.—Commentary In compiling Fig. 2, the greatest difficulty of all has been that of assessing the power appropriate to the high speed. The powers given in column 3 are those quoted by the various authorities stated in column 21. In order that the reader may appreciate fully the nature of any differences, Fig. 3 has been prepared giving such data as one can find for the engines concerned. Airspeed Courier.—There is no consistency whatever between the quoted values for weights, wing area, power, and loadings. Wing area 250 and wing loading 13.5 give .gross weight 3,370. Power 240 and power loading 15.7 give gross weight 3,770. Weight empty 2,100 and load 1,690 give" gross weight 3,790. The quoted gross weight is 3,900 which, with load 1,690, gives tare weight 2,210. Stalling speed is quoted. Landing speed has been assessed proportionately lower taking the Envoy as a guide, q.v. The values for kLMAX seem rather high. Airspeed Envoy.—Two gross weights are quoted—4,900 as performance weight and 5,300 as C. of A. maximum. Wing loading appears to be quoted on maximum weight, and power loading on performance weight and normal power. I have adjusted the loadings to performance weight and maximum power. Armstrong Atalanta.—Pcrwer loading 12.2 appears to be quoted on a maximum power of 470. I have been unable to discover a Jaguar type giving 470 maximum at 4,000ft.—the height at which the top speed is quoted. If maximum power 470 occurs at 4,000ft., the high-speed figure is 18.7. If, however, this power refers to sea level and is not maintained to height, the corresponding high- speed figure is estimated at 21.4. Avro 642.—Tare weight quoted at 7,360 is exclusive of radio equipment 90, which has been added to give tare weight 7,450. Power loading quoted at 12.8 appears to be on normal power 460 at 2,000 r.p.m. I have assumed that the engine is a geared Jaguar giving 490 maximum power at 2,200 r.p.m. The power loading has been estimated on this figure. Stalling speed is quoted. Landing speed has been assessed as for the Courier. Avro 652.—Power loading quoted at 12.24 is on normal power. On the maximum power 305 the power loading is 10.8 The corresponding wing powers are 1.32 and 1.49, respectively. These adjustments reduce the high-speed figure from 27.6 to 24.4. Avro Commodore.—From the quoted figures for wing area 307, wing loading 10.82, power 215, and power loading 14.45, the gross weight is returned at 3,320 instead of 3,50a as quoted, reducing the weight ratio from 1.57 to 1.49 and increasing the span loading from .40 to .42. If we accept gross weight at 3,500 and wing area at 307, then the wing loading will increase to 11.4, and the wing power to .74, reducing the high-speed figure to 20.2, and raising KLmax. to .89. The corresponding power will be 227. Blackburn Feeder &-In view of the high value of the weight ratio I suspect that trie tare weight quoted at 4,740 is exclusive of equipment, although the Ehmcanson spar
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