Flight, February 1922
THE ERNOUL COMMERCIAL MONOPLANE "F.A.T.M.A.2"
An Interesting French Machine now being built
AT the Paris Aero Show, held in the Grand Palais, during November last, there was exhibited, on the stand of Aero Transports Ernoul, a large scale-model
of a very interesting commercial monoplane which is now being constructed for this firm at Toulouse. It is to be regretted that the actual machine could not be finished in time to be exhibited, as the model appeared to indicate that the machine will be of more than ordinary interest. M. Ernoul is head of the firm which has been operating the Bordeaux-Toulouse-Montpellier air service, and which it is proposed to extend during this summer by a line running from Bordeaux to Marseilles, Geneva and, possibly, Constantinople and the East. It is considered that for this service a machine of high-speed and good range is essential.
The Ernoul commercial monoplane has been designed by M. Dewoitine, and, as will be seen from the accompanying illustrations, is of somewhat unusual design. It is a monoplane of the cantilever type, i.e., without external wing bracing, and resembles the "D.H.29," in having a pronounced taper to its wing. In other respects, however, it has no resemblance to that machine. We have no information relating to the wing section used, but judging from external appearances, it is one of the Gottingen sections, possibly No. 441.
The fuselage, which is of monocoque construction, has a good streamline form, and every effort has been made to reduce resistance to a minimum. The large cabin has seating accommodation for eight passengers, and, it is stated, that folding berths will be fitted so that passengers making long journeys will be able to lie down for a rest. It is difficult to see how room can be provided for sleeping accommodation in the space available, but possibly the passengers will take it in turns. The cabin is lighted by windows in the side, and as there is no lower plane, the view obtained is excellent. The pilot and a passenger or engineer are placed in front of the leading edge of the wing, and as the nose of the fuselage is very narrow, to clear the propellers, the pilot has an extremely good view forward.
By far the most interesting feature of the "FATMA" is, however, the placing of the engines. The arrangement was first suggested by Herr Dornier, of the Zeppelin company, photographs of a wind tunnel model of whose machine were published in FLIGHT of May 19, 1921. Briefly, the mounting of the engines consists in two cantilever beams, streamlined so as to reduce resistance, springing out laterally from the fuselage near the nose, and carrying on their outer ends the two engines. The main object of this arrangement is, of course, to get the two engines as close together as possible, so as to reduce the turning moment set up when one engine stops. By placing the engines well forward, and narrowing down the nose of the fuselage, the engines need be separated by little more than the diameter of the propellers used. It might be objected that for such a small machine, it is unnecessary to have two engines. While that is to a certain extent true, it must be pointed out that the machine is required to have a good performance, high speed, good reliability (owing to the difficulty of finding suitable landing grounds on the route contemplated) and long range. Thus, it might be rather a tax on a single engine to provide the necessary power for long periods. Furthermore, the designer may have been handicapped by the lack of a suitable single power unit, and with two engines placed so close together it should be possible - which is far from always the case with ordinary twin-engined machines - to fly on one engine only. In fact, the calculated performance figures for this machine indicate that with only one engine working (although at its full power, of course) the speed is 87 m.p.h.
A very practical advantage of the Dewoitine design is found in the ease with which the engines can be "got at" and overhauled, or replaced with new ones. In fact, we do not think we have ever seen a machine in which this can be so easily accomplished. As the engines are well forward of the leading edge of the wings, a tackle can easily be employed for lifting them off their bearers, or, if necessary, the entire engine nacelle can be lifted off and replaced. In the present design, the tanks are placed in the nacelles, behind the engines, but it would be an easy matter to transfer them to the top of the wing, and thus provide direct gravity feed. Altogether, it appears to us, that the Ernoul firm has chosen very wisely in adopting the Dewoitine design. There are few French designs which we like better, and this form of engine mounting, although it is probably somewhat heavier than the usual placing of the engines on the wings, is much more what operational firms are really wanting than are those of the majority of machines in actual use. There is, of course, no reason why it should not be adopted for biplanes also.
The main characteristics and estimated performance of the "FATMA," are as follows: Length o.a., 43 ft.; span, 72 ft. 3 ins.; wing area, 700 sq. ft.; weight empty, 3,590 lbs.; weight of fuel, 1,120 lbs.; useful load, 1,870 lbs.; total loaded weight, 6,580 lbs.; wing loading, 9-4 lbs./sq. ft.; power loading (on base of 500 h.p.), 13-2 lbs./h.p.; maximum speed at 6,500 ft., 127 m.p.h.; speed on one engine at 6,500 ft., 87 m.p.h.; landing speed, 46 m.p.h.; ceiling, 10,000 ft.; engines, two 250 h.p. Salmson C.U.Z.9, geared down; range, with full load, about 600 miles.