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Aviation History
1931
1931 - 0007.PDF
FLIGHT, JANUARY 2, 1931 when they are raised for going clown. The trailing edgesof the elevators are formed by a strip of aluminium, £-in. in thickness, and standing out rearwards for approximately1 in. In the earlier model, which, as previously mentioned, crashed in 1927, the front wing was so mounted that it couldbe moved see-saw fashion on its support, from the pilot's cockpit. This arrangement was adopted, as it was hopedto counteract, by moving it one way or the other, the effects of one of the engines ceasing to work in mid air. Now, however,the wing is held in a horizontal position by double cables at each side, while horizontal stresses are, to a certain extent,taken up by the wing tips being connected by cables with the tips of the main wing. Underneath the front wing,recessed in the fuselage, is a third wheel. Owing to the turning point of the 'plane lying so far backin front of the main wing, it was necessary to provide a very large rudder fin, to which is then attached a narrow andhigh rudder. There appear to have been difficulties to ensure the 'plane keeping on its course, for in addition to therudder fin, two further fins, of relatively large size, have been provided, one each side left and right underneath themain wing, about half way between the engine nacelles and the wing tips. These vertical fins are supported on bothsides by cables, and they are set at a slight angle to the axis of the fuselage in such a manner that, if their 'planes wereto be prolonged in a forward direction, they would meet some distance in front of the 'plane. All controls are operatedby wire cables running over pulleys. The weight of the complete 'plane, including the passengerappointments, is 2,585 lb., and it is capable of transporting a load of 1,045 lb., making a total flying weight of 3,630 lb.The maximum speed attainable is 88-5 m.p.h., whilst the cruising speed is 79 m.p.h., and the landing speed 51 -5 m.p.h.The 'plane climbs to 1,000 m. (3,280 ft.) within 8| min. These performances are not very exceptional but in a 'planeso young of development, they must be regarded as very good. As a matter of fact, most of the development hasbeen done in the wind tunnel and in the drawing office, and the makers were pleasantly surprised to find the machinebehaving so excellently as already to admit of its introduction in the passenger transport business. The writer has enjoyeda ride in the machine, and was struck with the relative noise- lessness in the cabin and the fine manoeuvrability in the air.1 lie makers say that they have gained so much experience in One of the Power Plants of the " Ente " : These areSiemens Sh-14 type, of 110 h.p. each. The under- carriage consists of a horizontal Vee and a telescopicstrut to the engine mounting. constructing this 'plane that they now feel capable of buildingany size " Ente " 'plane from a small sporting to the largest transport 'plane. SOME COMMENTS ON THE FOCKE-WULF "ENTE"W HEN trying to form an opinion of the merits or other-wise of the Focke-Wulf "Ente," one should bear in mind that, although it has now been approved by theGerman authorities for passenger-carrying, the machine is to be regarded as an experimental type, and it is to beassumed that improvements can be made in later machines. This supposition is necessary in order not to be unfair bybeing too critical, as one might well otherwise be. The de- signers do not claim for the " Ente " type either better aero-dynamic efficiency or more economical structure weight, what they do claim is a number of advantages not possessedby the orthodox type of aircraft, such as impossibility of stalling and consequent spinning, and virtual impossibilityof turning over on the ground, even when landing on very rough ground, or with the wheels locked by the brakes.Both these claims would appear to be supported not only by theory but by the very thorough flying tests carried outTK G ^le macrune was approved for passenger-carrying. J-hus the points in favour of the " tail-first " type of aircraftmay be summed up briefly as follows : It will not stall, in the sense that its main lifting surface cannot, by anymanoeuvre possible to the pilot, be made to exceed its maximum lifting angle. It will not spin, because before thisis possible the main wing must reach stalling angle, which it never does. It cannot turn over on the ground. This is,of course, an obvious result of the length of fuselage projecting ahead of the centre of gravity and of the wheels. One pointupon which we have no data is the loss of height incurred when the front lifting surface is stalled and the nose drops.A certain loss of height there must, presumably, be, but it would seem likely to be a good deal smaller than that whichwould result from a stalling of the main lifting surface. Apart from the actual loss of height, the worst case would,one presumes, be that in which the front lifting surface was stalled at such a height above the ground that the machinestruck while at its steepest angle, i.e., just as the nose had dropped, and before it had had time to rise again as a result mcreased speed gained in the dive. Much seems to depend upon that angle. If it is very great, serious damagemight result from striking the ground. If the angle is not very great, or in other words, if the nose does not, at themaximum angle attained, point downward very steeply, then it seems likely that, even in this worst case, the machinemight simply glide on to the ground without damaging itself. Turning to the other side of the balance sheet, it is not atall difficult to find room for criticism. For example, an examination of the figures reveals the fact that the ratioof gross weight to tare weight is only 1 -405, a figure which can only be described as poor. A ratio of gross to tare weightof 1 • 6 or more is reached in most British aircraft, and that with loadings (wing and power) lower than those of theFocke-Wulf " Ente." One British machine which is com- parable with the " Ente " in that it is of approximately thesame weight, power and wing area, is the Saro " Cutty Sark." This machine, as our readers will know, is a flying-boat, alsoproduced as an amphibian. In its plain flying-boat form the Saro " Cutty Sark " weighs fully loaded 3,700 lb., and thetare weight is 2,425 lb., giving a ratio of 1 -522 as compared with 1-405 for the " Ente." The difference in gross weightis but 70 lb., but the difference in tare weight is 160 lb., both figures being in favour of the " Cutty Sark." The wingareas of the two machines are approximately equal, and the engines are also of approximately the same power. On the subject of aerodynamic efficiency, the " Ente "cannot be described otherwise than as disappointing. With a wing loading of 9-77 lb./sq. ft. and a power loading of 16-5lb./h.p., the maximum speed given is only 88 m.p.h. With approximately similar loadings, the Saro " Cutty Sark "has a maximum speed of 105 m.p.h. It is a little difficult to account for this disappointing performance. The Everting" High-Speed Figure " is only 8-04 which is extremely low. The corresponding figure for the " Cutty Sark " is 11. Thus,assuming equal propeller efficiency, the minimum drag coefficient of the "Ente" is 1-375 times as great as thatof the " Cutty Sark." There is no very obvious explanation of this. The " Ente " looks fairly " clean," although the" whiskers," in the form of large clumsy cranks, on the for- ward plane might produce a certain amount of unnecessarydrag, as probably does also the fuselage flying " wrong end on." Ih
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