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Aviation History
1943
1943 - 1994.PDF
•168 FLIGHT AUGUST IZTH, THE TANDEM MONOPLANE more was heard of it. It was not until the Itford glider meeting of 1922 that we saw a tandem monoplane in the air. This was the little single-seater glider designed and built by the Frenchman Peyret and flown by his compatriot Maneyrol to such good effect that it won the prize. Louis Peyret's effort was in fact a very creditable one. The two wings were of the same area, and as the pilot sat by the trailing edge of the front wing, the weight dis- tribution was probably reasonably correct. Front and rear wings had ailerons, and the control was so arranged that the four flaps worked together, front and rear wing flaps in opposition for elevator effect, and in unison for aileron con- trol. Maneyrol, when he finally did get into the air on the last day of the meeting, lemained aloft for 3 hours 21 minutes, and proved that the tandem Peyret had one thing which all the other gliders lacked: controllability. The aerodynamic efficiency was much inferior to that of the high aspect ratio orthodox gliders, but the controllability did enable the pilot to keep the machine in the up-currents and thus to " sit" for as long as the wind lasted. Not Followed-up Aftei the Peyret-Maneyrol success it might have been expected that someone would have attempted to apply the tandem wing principle to power-driven aircraft. No one appears to have done so. The reason probably was that in those days, when we thought of light aircraft, we thought in terms of very small engines, motor cycle engines, in fact, as was shown the following years at the Lympne light aircraft trials. The tandem wing was believed to be so inefficient as to be ruled out for aircraft that had to fly with a minimum of power One somewhat abortive attempt was made by trre French designer Henri Mignet with his " Pou-du-Ciel." That little machine was by way of being a tandem monoplane, but the overlap of the two wings placed it somewhere between the tandem and the biplane, and the "slot effect" was so pro- nounced that it tended to swamp the tandem characteristics. Mignet did effect a cure of the vices of the original machine by fitting both wings with flaps, thus approaching the Peyret glider arrangement somewhat, and he may yet "produce something practical. Whether or not the tandem monoplane might be worth reviving for certain specific purposes is an interesting specu- lation. The fact that the type has not hitherto received much attention does not necessarily prove that it is not capable of development. Modern aerodynamic knowledge, with so many wing sections from which to choose and with s iOwuu-v-ij Wets iiOi -i uiy a. lanciem mono- plane, the slot effect be ng predonvnant. Maneyro! on the Peyret glider setting up a record of 3 hr.21 min. 7 sec at Firle Beacon in 1922. Both wings had flaps, nterconnected to operate as elevators and ailerons Therudder was probably ineffective. ._ very effective flap arrangements capable of application,might put a very different complexion on the whole matter. I have referred to the somewhat vague notions we had in 1910 of the advantage of the tandem-wing arrangement, There is little doubt, however, that the location of th centre of gravity is rather less critical than is the case with the orthodox monoplane. Its movement fore and aft, unless carried to extremes, should do little more than vary the proportion of load carried by the two wings, * matter which could probably be taken care of by a small change in the front-wing incidence. The speed range might be slightly reduced, due to the fact that the rear wing is never permitted to reach : laximum lift before the front wing stalls. To offset that, both wings are lifting and there is no tail to produce a down-load. Basically there is, of course, some similarity between the tandem monoplane and the tail-first machine. It is mainly a question of the relative size of the two wings. In the tail-first the front wing is "elevator size," but if it grows a point is reached where it is difficult to say whether the machine is tail-first or tandem. Both share the fundamental condition that for longitudinal stability the front wing must be more heavily loaded than the rear, and, if the wiiiigs have the same section, must be flying at a greater an\le of incidence. Then the front wing, or front elevator in the tail-first, will stall before the other. In the tail-first type that should make spinning impossible, since the rear or main wing is never permitted to reach stalling angle. With the tandem-wing arrangement the front wing, when stalled, might have a tendency to spin. This, presumably, would be resisted by the rear unstalled wing, and the two would have to "fight it out" between them. Directional control and stability are something of a prob- lem with the tail-first, the tailless and the tandem wing arrangements. With tandem wings, however, it would appear that such powerful controls could be incorporated in the trailing-edge flaps that the customary third control could be omitted. In the Peyret it is doubtful if the small rudder was of much use. Two control aircraft of faiiiy orthodox type have been built, and the tandem wing might afford another avenue of approach to that subject. Drag rudders on the wing tips should, in any case, be capable of giving all the rudder control necessary. If tandem wings were lound to give adequate control without a rudder, any aerodynamic inefficiency of the arrangement might be tolerated for the sake of the greater simplicity of piloting. In that case the vertical surfaces nt the wing tips would act as fins only. If and when jet pro- pulsion becomes an accepted fact, the absence of a tail would facilitate installation. " For certain military purposes there might be a good deal to be said for wings in tandem especially in the smaller classes of aircraft. A twin engined two seater fighter, lor example, could, by suitable location ol the main loads, be given an excellent field of fire for the rear gunner and an unobstructed view for the pilot. C, M. lJ.
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