Flight, December 1924

The Paris Aero Show 1924

SOCIETE INDUSTRIELLE D'AVIATION LATECOERE

   THERE are two Latecoere stands at the exhibition this year - one in the Grande Nef and a smaller one in the side building or annexe opposite to the main entrance. On the large main stand are shown two machines - the Lat. 15 and the Lat. 16 - while on the smaller stand is a Lat. 17. All are commercial machines, if by "commercial" one does not necessarily mean "economical" machines.
   The Lat. 15 is a twin-engined sesquiplan whose two 220 h.p. Lorraine-Latecoere engines are mounted on short wing stumps growing out of the sides of the central fuselage. In judging the Latecoere machines it should be borne in mind that they are all designed for rather special conditions, and that, therefore, it would be unfair to compare them with British or German commercial machines designed for use under totally different conditions. Thus the Toulouse-Rabat-Casablanca route, operated by Latecoere with great success for several years, requires long distances to be covered without alighting, and the machines used must have a fairly high cruising speed in order to be able to combat head winds of considerable force. If, therefore, the power expenditure per passenger carried or the useful load per horse-power, appears somewhat uneconomical, one should not on that account hastily condemn the machines as being "uncommercial." The records of the Lignes Latecoere show that extraordinarily good work has been, and is being, done over a most difficult route, and the existing routes, it should be remembered, are about to be extended to Dakar, with a maritime service to Pernambuco. It is, perhaps, difficult for British readers to realise the difficulties which the regular operation of such a service imposes, but it may be taken for granted that they are very great, and we think every credit is due to M. Latecoere for having had the courage to initiate them and the tenacity to maintain them in spite of all obstacles. With this brief introduction we may turn to the machines themselves.
   The Lat. 15, as already mentioned, is a twin-engined machine with the two Lorraine engines placed very close to the main fuselage. The latter is of excellent streamline form, as are also the engine nacelles; but it would appear likely that placing three streamline bodies as close together as they are in the Lat. 15 must necessarily result in a considerable increase in head resistance, so that the trouble taken in streamlining the individual bodies may be largely wasted by placing them so close together. One realises, of course, that the designer desired to keep his two power units close together so as to reduce the turning moment when one engine stops. (The Lat. 15 was, as a matter of fact, flown on December 2 for one hour at 1,000 m. on one engine of 250 h.p., and carrying a useful load of 2,350 lbs.) As exhibited at Paris the Lat. 15 is fitted up to carry six passengers only, which seems a small number for 440 h.p. (i.e., 73 1/2 h.p./passenger). It should, however, be pointed out that the total useful load of the machine is more than 2,000 lbs., so that in addition to the six passengers a considerable amount of luggage and/or goods can be carried. The exact amount of pay load available will, of course, depend upon the length of the stages that have to be flown without landing. For a range of 500 km. (312 miles) the useful load is 1,200 kgs. (2,640 lbs.), while for a range of 2,000 km. (1,250 miles) the useful load is 355 kgs. (780 lbs.). These figures may be said to represent the two extremes, and, of course, any intermediate combination of range and pay load is possible. They show that the Lat. 15 is a good, deal more useful than a mere mention of the number of passengers for which there is accommodation would indicate.
   Constructionally the Lat. 15 is of the composite type, with duralumin wing spars, wood ribs and fabric covering, while the fuselage is a duralumin tube structure with duralumin covering in front and fabric covering at the rear. The wing bracing tubes slope outwards from the lower wing stumps, and under each engine there is a two-wheeled under-carriage. The propeller tips pass very close to the nose of the fuselage, and it might be expected that considerable propeller "flutter" and vibration might arise. The pilot's cockpit is in the extreme nose of the fuselage, and the view forward should be excellent, although sideways it is probably somewhat restricted by the engines, as these are much farther forward in relation to the pilot than in British twin-engined machines.
   The main dimensions of the Lat. 15 are: Length overall, 11-84 m. (38 ft. 10 ins.); height, 3-72 m. (12 ft. 2 ins.); wing span, 18 m. (59 ft.); wing area, 54 sq. m. (582 sq. ft.). The weight of the machine empty is 1,650 kgs. (3,630 lbs.); with a fairly average proportion of fuel to paying load the total loaded weight is 3,135 kgs. (6,900 lbs.), the load being made up as follows: Crew, 175 kgs. (386 lbs.); fuel and oil, 370 kgs. (814 lbs.); pay load, 940 kgs. (2,070 lbs.). At ground level the maximum speed is stated to be 180 km./h. (112-5 m.p.h.), and the cruising speed is 150 km./h. (94 m.p.h.).
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