Flight, February 1923
SOCIETE D'EMBOUTISSAGE ET DE CONSTRUCTIONS MECANIQUES, Colombes (Seine)
The S.E.C.M. type XXIII is intended for touring, and in general arrangement is similar to the new Bristol three-seater, although it is a much larger machine.
The pilot sits in front, between the wings, and the passengers' seats are placed behind the wings, side by side. The machine is built of metal throughout, excepting the covering, and the engine is a 180 h.p. Hispano-Suiza run normally at 160 h.p. Thus, the engine is considerably more powerful than that of the Bristol, which has a 100 h.p. Lucifer. The wing area is 26 sq. m. (280 sq. ft.), and the speed range. 180 km. (112 m.p.h.) to 60 km. (37 m.p.h.).
The third machine exhibited, a touring and school type side-by-side two-seater, was shown in skeleton, and consequently was by far the most interesting, as the details of the metal construction could be thoroughly examined. Consequently this type, the XXII, will be dealt with at greater length, keeping in mind that many of the constructional features are common to all three machines.
The fuselage of the S.E.C.M. XXII is constructed entirely of Duralumin tubes, joined together by very elaborate sheet Duralumin fittings wrapped around the longerons and struts. The details are shown in the accompanying sketches. Riveting is everywhere employed for joining two pieces of metal, or the edges of a folded piece, but it would appear at any rate possible that a certain amount of unscientific design is found in the manner in which the sockets terminate on struts and longerons. We believe we are correct in stating that several British constructors have found that where a tube end is housed in a socket there is likelihood of the tube cracking just at the edge of the socket, unless this is thinned down to a feather-edge. This precaution does not appear to have been taken in the S.E.C.M. machine, and it is possible that trouble will arise out of this omission. The workmanship of the fitting, as indeed of the whole of the construction, is excellent, and it is claimed that the makers have discovered a method of rendering the metal immune from corrosion.
The wing construction is, if anything, neater than that of the fuselage, and is considerably "cleaner" than on the majority of the all-metal machines. To a certain extent this is due to the fact that the spars are merely rectangular, section Duralumin tubes, so that no latticework, riveting, etc., is required. Whether such a tube is very economical is another matter, but its use certainly makes for simplicity. The ribs are of U-section, but the edges are pinched together so that the actual rib flanges almost become tubes, open on one side and having projecting flanges. The vertical web struts and diagonal ties are stamped from the flat sheet, and are given three corrugations, as indicated in one of the accompanying sketches. In between the main ribs are short nose ribs, also stamped from sheet, and having the, edges turned over to form channel sections.
As the rear spars are placed relatively far forward in the wing section, in order, no doubt, to retain a spar of reasonable depth, the ailerons are hinged to a false rear spar of channel section. The details of this spar are shown in the top left-hand sketch. The ailerons themselves are of a construction similar to that of the main ribs, with a tubular leading edge, a wire trailing edge, and a channel section stringer running parallel to the spars approximately midway in the aileron chord. The strutting and bracing of the wings are of usual type.
The Hispano engine is mounted on a very simple framework in the nose, and carries a nose radiator with shutters of normal type. An undercarriage of the usual V-type, sprung by rubber shock absorbers, completes the structure. The tail surfaces are of similar construction to that of the main planes, and in shape are quite orthodox.
The use of all-metal construction in a machine intended for school work is probably, a novelty, but although repairs might be somewhat difficult to effect, the rough usage of a machine employed for school purposes should very quickly show up any defects that might exist, and thus assist in perfecting the design in a shorter time than would be possible in a machine used very gingerly.
The main characteristics of the S.E.C.M. XXII are as follows :- Length, o.a., 6-9 m. (22 ft. 8 ins.); span, 9-5 m. (31 ft. 2 ins.); wing area 22 sq. m. (237 sq. ft.); total loaded weight 820 kg. (1,805 lbs.); wing loading 8 lbs./sq. ft.; power loading (on full power), 12-7 lbs./h.p.; engine 150 h.p. Hispano, run normally at 130 h.p.; estimated speed at 2,000 m., 180 km. (112 m.p.h.); landing speed, 60 km. (37 m.p.h.).