Flight, January 1932

The Latecoere Lat. 300
France is pursuing a vigorous policy of flying boat development. Recently we announced that Bleriot is building a 20-ton flying boat, and below we give particulars of a new Latecoere of approximately the same weight which has already made its first test flights. The machine is intended, if it comes up to expectations, for the South Atlantic mail service. [Since this article was written and set in type we have had news that Lat. 300 was sunk during a test flight. Details are not at present available. – Ed.]

   GREAT BRITAIN has, for a number of years, held a leading position in the production of seaworthy all-metal flying boats. That this position would not remain unchallenged for long was a foregone conclusion, and among the nations which are striving seriously to catch up with us is certainly France. For many years the French policy was to design marine aircraft intended to operate from fairly sheltered waters, and the types produced under that policy could not, indeed were not, intended to compete with British flying boats for seaworthiness. Lately, however, there appears to have been a decided change in policy where French marine aircraft is concerned, and an endeavour is now being made to meet the new conditions. It may, perhaps, be recollected that some time ago France bought from Short Brothers a "Calcutta" flying boat fitted with Gnome-Rhone "Jupiter" engines. That the purchase was made in order to provide data and information for French flying-boat designers was fairly obvious, and was actually sound common sense from the French point of view. The firms on the other side of the Channel have now had time to get going, and as the French Government has now given them the opportunity for which they had been waiting, progress may be expected to be rapid.
   The Latecoere type 300 described below is quite obviously not in any sense a copy of the Short "Calcutta," and whatever influence the British machine may have had on design, it is not visible in such external views as have been published. If it is a question of "copying," as in fact it scarcely seems to be, there is more similarity between the Lat. 300 and the Dornier machines, in that there is a flying-boat hull surmounted by a monoplane wing on which the engines are carried, while lateral stability is obtained by short wing stumps springing from the sides of the hull. This general type of layout has been used by the Latecoere firm for many years, and the present machine is, in fact, a development of an earlier type, the 380, but fitted with four instead of two engines. When we state that the type 300 is being followed by a still larger machine of 4,000 H.P., it will be realised that this famous Toulouse firm is very much in earnest about developing the transatlantic type of flying boat.
   For the data, etc., of the Lat. 300 which follow we are indebted to our excellent French contemporary Les Ailes, whose Editor-in-Chief, M. Georges Houard, is one of the best friends British aviation has in France, his comments being always scrupulously fair and just, while his willingness to give any British aircraft or flight of merit prominence in his paper is well known and in considerable contrast with certain French aviation journals.
   The Latecoere type 300 is of all-metal construction, the material used being mostly aluminium alloy, although steel fittings are used here and there. The main monoplane wing has two duralumin spars, duralumin ribs, and fabric covering. The lower wing stumps, whose span is 13 1/2 metres (44 ft. 3 in.), are planked with light metal. The ailerons are balanced by narrow-chord auxiliary surfaces hinged to the aileron trailing edges and moving in the opposite direction to the ailerons. A similar type of balance is used for the elevators and rudder.
   The boat hull is of all-metal construction, but details are not available. The shape of the hull is, it would seem, a combination of British and French practice. The two steps usually found on British flying-boat hulls are used. Hitherto French flying-boat designers have shown a marked preference for the single-step hull. The vee bottom is used, but the vee is less pronounced than in most large British flying boats. From the chines upwards the Lat. 300 hull is quite different, the bulkhead being approximately of semi-circular form. The machine is large, it is true, but the freeboard appears low in comparison with British practice. Put differently, the ratio of height to beam seems much lower than in British boats. At the stern the hull is raised considerably, and ultimately forms the fixed fin to which the rudder is hinged.
   The wing stumps are of biconvex section, and are used, in addition to their function as lateral stabilisers when the machine is on the water, as part of the wing bracing structure, the struts running to the engine mountings and to the outer wing pieces being anchored to the stumps. Triangulation is carried to a considerable extent, and wire bracing is entirely absent.
   The interior of the hull is utilised largely for the accommodation of the great quantities of fuel which the machine will have to carry for a flight across the South Atlantic. In the forward part of the hull is the marine equipment, etc., and behind that is the cockpit, with two seats side by side and dual controls. Aft of that is the wireless cabin and a small resting cabin for the crew. No passenger accommodation is provided, as the machine is intended for mail carrying, the pay load for the estimated range being 500 kg. (1,100 lb.), which will not take up much space.
   The four Hispano-Suiza engines, type 12Nbr., of 650 h.p. each, are mounted on top of the wing, in very elongated nacelles, two engines being tractors and two pushers, so that a considerable separation in a fore and aft direction was necessary in order to get the airscrews clear of leading and trailing edges of the wing. Fuel supply must of necessity be by pump, and A.M. pumps are used. In addition there is a hand pump for use in emergency, although one does not envy the member of the crew who has to supply fuel to some 2,500 h.p. Engine starting is by an auxiliary engine installed in the crew's quarters.
   It is intended that the machine shall normally carry a crew of four: first pilot, second pilot, wireless operator, and engineer. It is calculated that with 10,970 kg. of fuel the machine will have a range of 3,250 km. against a constant headwind of 30 m.p.h.
   The main data of the Latecoere 300 are as follow :- Length overall, 25.83 m. (84 ft. 9 in.); wing span, 44.2 m. (145 ft.); wing area (including stumps), 306 sq. m. (3,600 sq. ft.).
   The tare weight is 10 613 kg. (23,350 lb.), and the maximum permissible gross weight 22 440 kg. (49,370 lb.). The load is divided as follows :- Pay load, 500 kg. (1,100 lb.); fuel and oil, 10 970 kg (24,150 lb.); crew and their equipment, food, etc., 357 kg. (785 lb.). It will be seen that the ratio of gross weight to tare weight is 2.11, which is an exceptionally high ratio, the machine carrying more than its own weight in load. The wing loading is, moreover, 13.7 lb./sq. ft., which cannot be regarded as unduly high for a machine of this type. To have achieved such a ratio of gross to tare weight for so low a wing loading appears something of a feat.
   Performance tests have not yet been made, but the estimated performance figures include the following :- Maximum speed at sea level, 202 km./h. (125 m.p.h.); service ceiling, 4 100 m. (13,450 ft.); range against 30 m.p.h. headwind, 3 250 km. (2,000 miles).