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Aviation History
1928
1928 - 1004.PDF
OCTOBER 25, 1928 The B F.W. M23 low-wing mono- plane with 20 h.p. Mercedes en- gine. Note the starboard wing carried on the side of the fuse- lage for trans- • port. s m s low-wing monoplane two-seater with 20 h.p. Mercedes engine. The B.F.W. type M.21 is an equal-span biplane designed for school work and aerobatics. Its aerodynamic design is perfectly normal (using the expression in the British sense) and the machine follows British practice in that the wings are designed to fold back, a feature not frequently found on German machines. The flat-sided fuselage is of welded steel tube construction, without wire bracing, the struts being arranged diagonally to [" FLIGHT " Sketch The wings of the B.F.W. M.23 are dismantled by un-doing three catches, and are then carried on the sides of the fuselage. triangulate the structure. The wings are of wood con- struction, with ply-wood covering, but with normal inter- plane struts and wire bracing. As in British light 'planes the petrol tank forms the top centre-section, giving direct gravity feed to the carburettor. The cockpit arrangements are normal, with removable controls fitted in one cockpit so that when the machine is not being used for school work, the second set of controls can be taken out. The factors of safety are stated to be such that the machine may be used, in its two-seater form, for ordinary " stunting," whi^e as a single-seater it is strong enough for the latest evolutions, such as the outside loop, etc. The engine fitted in the B.F.W. M.21 is a Siemens radial, type S.H.I 1, but the designer informs us that if desired a different " nose " can be supplied to take the " Cirrus " engine. Following are the main characteristics of the B.F.W. M.21 : Length o.a., 7-32 m. (24 ft.) ; wing span, 10 m. (32-8 ft.) ; wing area, 20-8 sq. m. (224 sq. ft ) Tare weight, 460 kg. (1,012 lbs.) ; permissible load, 280 kg. (616 lbs.) : total loaded weight, 740 kg. (1,623 lbs.) ; Maximum speed 145 km./h. (90 m.p.h.) ; cruising speed, 130 km./h. (81 m.p.h.). Ceiling, 3,300 m. (10,800 ft.). Range, 500 km. (310 miles). The B.F.W. M.23 is of the low-power, low-wing monoplane type made familiar in recent years by the Klemm Daimler machines. Like these, it is fitted with the 20 h.p. Mercedes engine, and the ply-wood covered fuselage has its decking in the form of a sharp-ridged " roof." The wings, which taper in plan form and thickness, are of the typical Messerschmitt single-spar construction, and this fact has been made use of in arranging the folding. The two wing halves are fitted to the fuselage by three quick-release devices, two of which are situated at top and bottom res- pectively of the main spar, the third being place"d farther back in the section. After releasing the three catches the wing can be lifted off and placed on edge alongside the fuselage, where there are small brackets to support it. The exhibition machine is fitted with the 20 h.p. Mercedes flat twin engine, but the A.B.C. " Scorpion " Mark II can also be fitted and gives a considerably better performance. Furthermore, it is stated that the structural strength of the machine is such that for special purposes an engine like the Armstrong-Siddeley " Genet " can be used. The B.F.W. M.23 has the following main dimensions: length o.a., 6-9 m. (22-6 ft.); wing span, 11-83 m. (38-8 ft.) ; wing area, 14 sq. m. (151 sq. ft.). The tare weight is 200 kg. (440 lbs.) and the permissible load 210 kg. (462 lbs.), giving a total loaded weight of 410 kgs. (902 lbs.). The maximum speed with Mercedes 20-h.p. engine is given as 135 km./h. (84 m.p.h.), and the cruising speed as 110 km./h. (68 m.p.h.). the ceiling is 3,500 m. (11,500 ft.), and the range 500 km. (310 miles). The Espenlaub Monoplane For some peculiar reason, detail information concerning the little machine exhibited by Herr Espenlaub was difficult to come by. The machine is a parasol monoplane of all-wood construction, including the wing covering, designed to carry pilot and passenger. The wing, which is in one piece, is mounted on four ply-wood covered cantilever struts rising from the fuselage, and is attached thereto by four quick- release catches. For transport the wing is, presumably, detached and placed lengthwise, still resting on the four struts. The engine fitted is a 40 h.p. six-cylinder Anzani radial air-cooled. One of our photographs on the next page shows the general lines of the machine. 934
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