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Aviation History
1944
1944 - 0856.PDF
446 FLIGHT APRIL 27TH, 1944 THE TANDEM MONOPLANE s lent of the Piltdown man. Considered in the light of present-day knowledge, a design JK this kind shows some promise of eliminating most of the snags enumerated above for the three arrange ments (orthodox, tail -first and tailless), while possessing in a large measure their combined advantages plus some additional good features. The advantages which may prove to be possessed by the type of aircraft visualised form a formidable list. The more obvious of these features are itemised below: — 1. Both leading plane and main plane contribute to the total lift of the aircraft, and consequently the parasitic drag which is associated with the tail plane of an orthodox machine is eliminated. Tail unit drag for a clean aircraft often amounts to 10 per cent, of the total; consequently an increase in speed of over 3 per cent, may be obtainable. 2. With the conventional wing-tailplane sys^efn, the nose-down pitching moment which is associated with the centre of pressure movement due to increasing incidence calls for a maximum negative lift from the tail unit at the very moment when thj greatest overall lift is desired. This undesirable feature is greatly aggravated when high-lift flaps are fitted; the highly efficient extending aerofoil type are the worst offenders. With the layout under review the lift of the two planes is additive, and backward movement of the C„ calls for an increased lift on the leading plane to maintain trim. 3. Due to the division of lift between two wings, as on a biplane, and to the possibility of achieving an increased overall CL, a reduction in span should be possible with a consequent beneficial effect on the structure weight. .• 4. The elimination of the tail and the concentration^? the power plant weight near the C.G. should also result in a considerable reduction in length and struc ture weight, and this feature, together with the reduction in span, should result in increased manoeuvrability. 5. The- above-mentioned feature may be of great im portance in connection with the gas turbine power plant where the .ratio of consumable load-fixed load jmisl: be conadert'b^y higher than that associated with a rerJjaft>cating -engine and airscrew. It also greatly fafflfcates a submerged installation in the case of a central nswer„ plant. TricyclA ^njpag^gear leads itself much more readily to suchjJWlesign than yto the orthodox aircraft, on The American designer John Northrop has revived the tailless in modern times. This is a flying scale model of a large aircraft. The name Focke-Wulf is familiar nowadays. In the " twenties " the firm produced the Ente tail-first monoplane. The wing-fins were " toed-in " in order to improve directional stability. Note the enormous size of the central fin and rudder. which poor dynamic qualities often lead to discom- for when taxyiug and sometimes to structural failure. The damping elje^t of the front plane may make it possible to reduce the weight of the nose- wheel installation. 7. The field of view is greatly improved, particularly in a single-engined arrangement where a pusher air screw with its manifold advantages is an obvious choice. Moreover, the oil which is thrown out in such generous quantities by most constant-speed air screws is left behind instead of obscuring the pilot's windscreen. 8. For military purposes the advantages ensuing from the use of the whole of the fuselage for stowage of the bomb load and military equipment are obvious, while the layout is such that an almost unimpeded field of fire can be obtained. The smaller overall size, gives greater safety by reducing the target area, and the greater concentrat^sffof the load and power plants makes for economyln armour. 9. For commercial aircraft the low drag which may follow from the reduction in wetted area and parasite drag would result in greater economy of operation. The loading advantages mentioned above, aided by the absence of wing spars and supporting structure running through the fuselage at the C.G. of the air craft, will make for greater convenience and comfort, while another important feature should be the main tenance of a. more nearly level floor both on the ground and throughout the flight range. It should be noted that most orthodox aircraft pass through a fairly large incidence range when taking off and land ing, even if a tricycle undercarriage is fitted. The particularly good field of view for both pilot and pas sengers is also worth mentioning in connection with commercial applications. Full-scale Research Needed A number of secondary advantages also come readily to mjriaT as do certain possible disadvantages. The latter, however, seem less numerous than those which can be enumerated for the various design layouts which have been tried previously ; they are mostly connected with queries which can only be answered by intensive research, including full-scale flight experiments. Personally, I have no doubt that the conception has potentialities which would amply justify an energetic experimental programme. One obvious application of the idea would be an attempt at a fleet fighter aircraft having performance, armament and dura tion equal to the best of our land-based fighters. Such a machine would have been of untold value to the Nav^
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