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Aviation History
1950
1950 - 0099.PDF
FLIGHT, iq January 1950 he pretended to be an amateur, and a timid, ham-fisted creature at the controls of an aircraft. In fact, he was (and still is) an exceptionally gifted and experienced aero- nautical scientist, a very able designer and constructor of %r unorthodox aircraft, and a skilled experimenter (he *** ..Constructed and operated his own T^jn^ tunnel); that he is a| pilot of skill and courage is obvious to all who have seen Him fly. He possesses a strong sense of humour which is , _*aipt to express itself in wit (an attribute usually disagree- able to experts and authorities) ; and he has a strong will that is disinclined to humble itself before those in power. AH this may help to explain the sad pre-war history of the Pou. Actually, the fatal design-deficiency of the original H.M. 14 arose from the fact that in such a design the vital slot-effect disappears at small angles of incidence. In this condition the wing combination behaves as a single-wing system of pronounced camber ; it is unstable at the normal e.g. position, and the aircraft tries to assume a stable attitude. This means that it tries to fly inverted. The pilot is unable to prevent the tendency, as the front wing (which acts as elevator) becomes ineffective in the absence of slot effect. This also has a connection with the fact that The H.M. 294 single-seater has a 35 h.p. Aeronca engine. most of the victims were skilled pilots: they sensed that the elevator produced little effect and instinctively put the stick farther forward in an effort to fly faster (as would have been correct with a conventional aircraft); this very action produced the catastrophe. Mignet quickly realized the true position after partici- pating in full-scale wind tunnel experiments at Villacoublay in 1936 ; and he came to the conclusion that a sure remedy could be achieved by excluding the possibility of flight at small incidences. He tried three different design solutions in succession ("conjugated wings"; auxiliary conjugated elevator flaps in the after wing ; and strongly reflexed aero- foil section in the after wing), and thus ensured that no nose-dive could commence or be sustained without produc- ing a tail-heavy pitching moment with the increase of speed. Mignet fully achieved his purpose in the same year and demonstrated several modified " flying slots," besides publishing in detail the modifications which were required to make the H.M. 14 safe. But it was already too late. One has seen little acknowledgement that, after the intro- duction of these remedies, no further fatal crash occurred in any Pou-du-Ciel or derived aircraft, and that in 1938 a Mignet two-seater "flying slot" qualified for the French Certificate of Airworthiness (passenger transport) after more than 500 hours of actual flying trials in the aif. To-day, Mignet works in. Argentina, whence he emigrated after the death of his wife. It is, perhaps, significant that this jesting preacher in a desert of aeronautical procrastina- tion has now proceeded from his " Sky Louse " to a " But- terfly " (H.M. 294) and to a "Wild Beast" (as he calls it), the new H.M.300. But he still labels his " flying slots " proudly and with justification "Los Aviones mas Seguro del Mondo" (the safest aircraft in the world "). The two new types are built to the typical Pou formula, with two-control system, variable-incidence front wing as elevator, missing ailerons, and all. H.M. 294 is a single- Characteristic plan-form of the species—H.M. 294 from below. seater with an American-built Aeronca engine of 35 h.p.; H.M.300 is a three-seater with a 125 h.p. Continental flat four. Under construction is a two-seater with an 85 h.p. engine in the class of the Ercoupe or Luscombe Silvaire per- sonal aircraft. In the design stage M. Mignet has a high- speed single-seater of exceptionally low weight. In both new types shown in the accompanying photo- graphs the outer portions of the wings are foldable for transport and housing, as will be seen from the view of an H.M.300 under tow. A characteristic of all Mignet air- craft has been their extreme simplicity. The designer has found it hard to work in Argentina, and the non-avail- ability of some materials and accessories has made the two prototypes heavier than they were intended to be Never- theless, both aircraft perform well, though the engines are second-hand and somewhat deficient in output. Unbiased (or, more correctly, rather sceptical) passengers in the persons of professional aeronautical engineers have given glowing reports about the flying qualities of the H.M. 300. Praised in particular are the amazing manoeu- vrability and stability (in all directions), and the fact that the aircraft cannot be made to spin. An aerodynamical Comparative elevations of the H.M. 294 single-seater (top) andH.M. 300 three-seater. The latter has a 125 h.p. Continental.
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