Flight, September 1934

SIMPLIFIED FLYING
A French Experimenter, M. Henri Mignet, has produced an Aeroplane, the "Pou-du-Ciel" which neither stalls nor spins

   BEING the fourteenth which he has designed and constructed since the war, the latest product of the very active brain and hands of the French experimenter, Monsieur Henri Mignet, is not to be treated lightly, as the impractical endeavour of an aviation enthusiast to produce “something different." M. Mignet has persevered, and, after innumerable disappointments, he does appear to have produced a machine which, if not, perhaps, the last word, is, at any rate, a practical flying machine on which the designer has, up to the present, made nights totalling more than forty hours' flying and over eighty take-offs. Nonstalling and non-spinning qualities, coupled with simplicity of control, have been the ideals at which M. Mignet aimed. In his earlier models he did not quite achieve his object, but in his latest type, the Sky Louse, it would appear that he has evolved a practical solution.

Preventing the Spin

   Spinning always seemed to M. Mignet to be connected with ailerons and aileron control, and when he came to design the Pou-du-Ciel he decided from the start that he would have no ailerons. If he had none, he argued, they could not very well get him into trouble. The decision was a drastic one, it will be admitted. Since the Wright Brothers first evolved wing-warping, and coupled it to the rudder control, aeroplanes have had lateral control, in most cases capable of being worked independently of the other controls. M. Mignet found, when looking around at other aircraft, that such things as kites, parachutes, and airships had no lateral controls. Why, then, he asked himself, should an aeroplane be compelled to use a form of control which was getting pilots into trouble? The ability of the other air-borne contraptions to do without ailerons was due solely to the fact that they had pendulum stability. The centre of gravity was below the centre of support. Very well, then, he would make his aeroplane so that its c.g. was below the centre of lift. A low position of the c.g. and a high position of the wing should do the trick. If his vertical surfaces, such as fuselage sides and rudder areas, were properly disposed in relation to centre of lift, dihedral angle, etc., that should suffice. After experimenting for some months, M. Mignet did get his fin areas so disposed that it was impossible to get his machine to do an incorrectly banked turn. He proved it by fitting a transverse bubble level. Any turn that could be made at any speed of which the machine was capable failed to budge the bubble more than about 2 mm.
   And now what about the non-stalling qualities? M. Mignet argued that it was really rather absurd to fit an elevator which, if powerful enough to give him the control he wanted, would be capable of getting his wing into a stall. Well, let us do away with the elevator, he said. But we must have fore-and-aft control of some sort. What alternative is there? In the end, a wing arrangement was chosen which is somewhere between the heavily staggered biplane and the tandem monoplane. Actually, neither the one nor the other. The front wing is carried en parasol, the rear wing, which is also the tailplane and of smaller span than the front wing, lies on top of the fuselage. The trailing edge of the front wing is above the leading edge of the rear wing, and separated from it by a gap which is small if the arrangement is regarded as a biplane, but large if one looks upon the opening between the wings as a variable slot. M. Mignet states quite definitely that he does get a slot effect of sorts from the arrangement. The front wing is hinged to its supporting trestle, and fore-and-aft control is by altering the angle of incidence of this wing.
   Simplicity of piloting is achieved by doing away with any foot control. The "joy-stick" is universally mounted as in the orthodox aeroplane. Fore-and-aft movement alters the incidence of the front wing, and thus performs the function of an elevator. The directional control, a large balanced rudder at the stern of the fuselage, is connected up to the joy-stick by cables in such a way that when the stick is pressed to the left, the machine turns to the left, with the appropriate bank for the turn, owing to the relative position of e.g., centre of lift and centre of side area. When the stick is moved to the right, the machine turns to the right in the same way. The throttle is the only other control.

Leading Particulars

   A side elevation of the Pou-du-Ciel, reproduced by courtesy of our excellent French contemporary Las Ailes, shows the relative position of the wings. It does not show the unequal spans. From a photograph published in our contemporary, it appears that both wings have a straight centre-section of considerable span, and that the dihedral angle, is obtained by slightly up-tilting the outer wing portions. The span of the front wing is 6 metres (about 20 ft.). That of the lower wing would appear to be about 12 ft. The overall length of the machine is 3.5 m. (11 ft. 6 in.), and the tare weight 100 kg. (220 lb.).
   The engine fitted is an Aubier-Dunne two-stroke inverted two-cylinder air-cooled of 500 c.c. capacity. At 4,000 r.p.m. it develops 20 h.p., and continues to develop it. The airscrew is geared down, so that its maximum speed is 1,600 r.p.m. For prolonged climbing M. Mignet throttles down to an airscrew speed of 1,500 r.p.m., and when cruising at an airscrew speed of 1,350 r.p.m. with the throttle one-third open, the machine is, M. Mignet estimates, taking but 12 b.h.p. from the engine. He has had it up to 1,800 m. (5,900 ft.) in three-quarters of an hour, and his consumption (oil is mixed with the petrol) is 9 litres (2 gallons) per 100 km. (62 miles). A height of 12 metres (13 yards) is reached 250 metres (273 yards) from the starting point with no wind and from standing start. The machine cruises at about 100 km./h. (62 m.p.h.), and lands at 30 km./h. (say 20 m.p.h.). Materials for its construction cost M. Mignet 1,200 francs (not, of course, including the engine), and took him twenty-seven working days of ten hours each. This included the propeller, which is of beech wood and carved out of the solid chunk.
   A very simple undercarriage appears to be used. The wheels are carried on short, straight axles hinged inside the fuselage, and under the tail there is a pair of small wheels, side by side, connected to the "bloaters" of the rudder. Steering on the ground is therefore easy.

Flight, April 1935

PAVING the WAY for the "POU"
"The Pou Club" and British Constructors: An Engine Difficulty: Wheels Too Expensive: The Supply of Materials

   THINGS are beginning to move in the Pou World. Some time ago we announced, following a suggestion made by a Flight reader, the formation of "The Pou Club" within the Air League of the British Empire, Air Comdre. J. A. Chamier, C.B., C.M.G., D.S.O., O.B.E., Secretary-General of the Air League, appointing himself as first president and committee.
   Negotiations with M. Henri Mignet, the designer of the "Pou-du-Ciel," and author of the book “Le Sport de l’Air: pourquoi et comment j'ai construit le Pou-du-Ciel,” have been begun, and will, it is hoped, lead to better information and greater facilities becoming available to potential British builders of the Pou. In the first place, the Pou Club, which is to say Air Comdre. Chamier, has approached a publishing firm with the object of bringing out an English translation of the constructional chapters of M. Mignet's book. In the second place, the Club has obtained quotations from a number of British firms for the different materials required for the construction of the machine. In the third place, the Club has got in touch with a British firm concerning the marketing of a suitable engine at what is regarded as a reasonable price. Here it might be pointed out that engines are already in existence which would probably suit the Pou, such as the A.B.C. "Scorpion" of 34 h.p., and the Douglas motor cycle engine fitted in the B.A.C. "Drone," which is of some 17 b.h.p. The former is rather more powerful than necessary, but would probably give the machine a very good take-off, while the latter is a little under the power used by M. Mignet, a more serious objection to its use being, perhaps, that it is direct-drive, and cannot, therefore, be expected to give quite as good a take-off as M. Mignet's geared Aubier-Dunne two-stroke.
   To make an English text of M. Mignet's constructional chapters available quickly, it has been decided, pending the publication of the English book, to translate the essential chapters into English. This work will be done by the Pou Club for the benefit of its members, who are advised to obtain the original French book for the sake of the drawings and sketches. This will enable them to get on with the work, even if they do not read French. A charge of 7s. 6d. is made for the translation. This amount will go towards the price of the English book when it is published. Should negotiations with the publishers fall through, the amount will be retained by the Pou Club as the translation fee. And, finally, should M. Mignet object to English translations of some of his chapters, the money will be returned, and the expense incurred will be "written off" as part of the Air League's service to the Pou Club. All of which sounds complicated and rather as if the Pou Club had failed to make proper arrangements with M. Mignet.
   A list of prices of materials for the Pou, obtained by the club from manufacturers, indicates that it should be possible to buy all wood, tubing, sheet, bolts, fabric, etc., for approximately ?25. The two largest items, as might have been expected, have proved to be the engine and the wheels. It is expected that a suitable engine may be available for a price of approximately ?60. A well-known firm has quoted ?4 13s. 6d. per wheel and tyre, which seems rather expensive in view of the fact that serviceable wheels can be bought in France for about 25s. each.

Flight, August 1935

L'AUTRE AVIATION
Henri Mignet Flies in England: Air Ministry Test Suggested
By C. N. COLSON

   LAST Saturday M. Henri Mignet, ably assisted by Madame Mignet, flew his "Pou" at Shoreham Airport. This was the first of a series of demonstrations taking place in England during the next three weeks.
   Flight has kept its readers fully abreast of "Pou" developments since M. Mignet first announced, to a somewhat sceptical French flying public, that he was going to fly without ailerons or rudder-bar, and that he was going to do it with greater safety than is provided in normal aeroplanes. It was, therefore, with the greatest interest that I went to Shoreham last week-end to see this interesting pioneer himself.
   He is not at all the dogmatic type of inventor usually associated with radical developments. He is just a vivacious Frenchman of small build, with a petite and equally vivacious wife. Together they have undoubtedly produced a machine worthy of the closest investigation. Opinions differ as to whether safety in the air is to be obtained by the elimination of the ailerons or the rudder. There are both schools of thought among aircraft designers, but so far there has been more experiment with machines lacking a tail rudder than with those lacking ailerons, as, for example, the "Pterodactyl" in England and the Waterman "Arrowplane" in the U.S.A.
   After seeing the "Pou" and its flying capabilities I feel that any money involved would be well spent if the Air Ministry were to acquire a "Pou" and test it thoroughly with a view to giving all manufacturers the benefit of the result of the tests. It is too early to say whether "there is anything in it," but it certainly seems a promising path down which Martlesham Heath or Farnborough might well send some of their experts at Government expense.
   On Saturday M. Mignet was flying a new machine built for him by Felix Louis, a French aircraft constructor, at Pantin, with the Aubier et Dunne two-cylinder inverted two-stroke engine (Flight, April 11, 1935). The machine was well made for its type, although certain details are a little crude in comparison with English aeronautical practice. Apparently M. Mignet is so busy with demonstrations that he now has little time for building his own machines, and, with the exception of a two-seater, in which he is going to teach Madame. Mignet to fly, he has no construction on hand at the moment. I learnt that he has now flown some 145 hours in "Pous" and that, contrary to general belief, he has tried piloting conventional aircraft, but I gather that the results did not encourage him to continue; in fact, they made him more than ever convinced that his "Pou" was a better method of flying.
   Before making his demonstration he broadcast a talk about flying and the "Pou," describing the latter amusingly as "a small insect which has made people in France scratch their heads."
   Starting up seemed to call for a considerable amount of energy. The airscrew had to be twirled round many times before the entitle was deemed ready, and then the actual start appeared to be dependent upon swinging the airscrew so hard that it turned over several compressions. The cockpit contained quite an array of instruments. Across the ample-sized dashboard, from left to right, I saw an A.S.I., a variometer, a revolution counter, an altimeter, and a home-made variometer. Beneath them were: dock, compass, and air thermometer.
   There has, according to reports, been a large number of crashes in France among the fifty "Pous" which are already flying out of the 500 being built, and most of these crashes are said to have occurred during the take-off. I therefore watched this initial stage of the flight very closely. I asked M. Mignet if there was any special difficulty to be anticipated during the stage when the machine was gathering speed over the ground, but he did not seem to think that the controls need be touched very much. Certainly his own take-offs showed no signs of any necessity for coarse use of the rudder.
   The "Pou" seemed extremely easy to manage on the ground, and the steerable tail wheel turned it in its own length without difficulty. In flight there was evidence of adequate control even when doing steep turns close to the ground and the spectators, but somehow the general feeling could not have been better summed up than by the remarks of a small girl, aged about four years, to her equally small brother when her piping, pedantically correct wording announced: "It doesn't appear to be very safe, Harold; it looks as if it might slide to one side at any moment!" It somehow didn't look as if the pilot was always certain of what it was going to do. This was probably because lateral stability is dependent upon the large dihedral angle and use of the rudder; the result is a sort of swaying recovery when a wing drops.
   The take-off was only a very few yards long, and the landing equally short; even a landing from altitude without the engine running was carried out without apparent difficulty as the glide was very steep.

Flight, April 1936

MODERN LIGHT AIRCRAFT REVIEW

POU-DU-CIEL

   EVOLVED by a Frenchman, M. Henri Mignet, the Pou-du-Ciel differs from other aircraft in that it has no ailerons for lateral control. The large dihedral of the wings gives the machine a pendulum action so that when the rudder is moved the machine automatically banks to the degree appropriate to the turn. The rudder is operated by moving the control stick from side to side, and the front wing is pivoted so as to have a variable angle of incidence; this takes the place of the elevator of the orthodox aircraft and is operated by moving the control stick forwards and backwards. The feet are not used at all in controlling the Pou.
   Although the Pou-du-Ciel was originally designed for amateur construction, and large numbers have been so built, several firms supply the machine complete, ready to fly. It is also available with different power plants, such as the water-cooled Carden, the Aero Douglas fiat twin, the British Anzani inverted vee twin, the Scott "Flying Squirrel" two-cylinder two-stroke, and, just lately, the Austin Seven engine adapted to Pou work.
   One firm which makes the complete Pou is the Putnam Aircraft Co., of 407, Hornsey Road, Holloway, London, N. Their machine is fitted with the Carden four-cylinder water-cooled engine and sells at L175. It differs somewhat from the original machine. For instance, the front wing has its leading edge covered with plywood up to the spa. The incidence control is of the rigid type, and the rudder controls are taken direct to kingposts on the rudder. In addition to the standard instruments, an oil pressure gauge and a radiator thermometer are fitted.
   Aircraft Constructions, Ltd., of Sidcup, Kent, supply all parts and also the complete machine. When fitted with the British Anzani engine the price of their complete machine is L157 10s.
   Abbott-Baynes Aircraft (a branch of E. D. Abbott, Ltd.), Farnham, Surrey, have an improved type coming through, but, unfortunately, are not quite ready to disclose details.
   Anything from a nut to the complete machine is also supplied by Purkess Light Aircraft, Ltd., of 204, Ballards Lane, Finchley, London, N.3, and complete parts can be obtained from Snellings Light Aircraft Service, 404, Blackburn Road, Darwen, Lanes, who are also distributors of the Anzani engine.

Flight, May 1936

A CANTILEVER "POU"
Performance and Appearance Improved: Greater Strength for Less Weight

   ONE of the disadvantages of the "100 per cent. Mignet" Pou-du-Ciel is that, with the cable controls below the wing, there is nothing but a slender telescopic strut to hold up the trailing edge when taxying, and the wing flaps rather alarmingly at times. Also, should the pivot be a little too far back, the centre of pressure can move ahead of the pivot and bring the trailing edge down, thereby causing the wing to stall. A dive may follow, and accidents which have occurred are thought to have been due to this. Introducing a rigid type of control, in the form of tubular struts from the operating cranks to the wing, gives the pilot the means of holding the trailing edge up, but then another possible trouble may arise. Should the wing be subjected to a down-lead in flight, it has little strength and may collapse. Top bracing would probably cure this, but would add still more drag to a wing which is already plentifully supplied with that commodity.
   Mr. L. E. Baynes has designed, and Abbott-Baynes, of Farnham, have built, an improved Pou in which all these problems were taken into consideration. Mr. Baynes decided to make the wing of cantilever form, and in this way it is as strong under down-loads as under normal up-loads. He has retained the single spar (of box section, however), but uses a different wing section (do not tell M. Mignet, but it has a rounded leading edge!), and carries the wing on two tripods, very much in the manner made familiar by the upper wings of the Fokker biplanes.
   On the two points of, these tripods the front wing is carried in trunnions, and may be detached by withdrawing two pins. When the control struts have been disconnected, the wing can be lifted off the fuselage. The rear wing is, of course, carried directly on the top of the fuselage. Dismantling or erecting the wings occupies but three or four minutes.
   To avoid any possibility of wing flutter, Mr. Baynes has incorporated a mass balance system. Apparently it has not occurred to anyone before that a wing pivoted as is the front wing of the Pou might need a mass balance; yet it is fairly obvious that such may well be the case. A mass balance on the wing itself would have been very heavy, and Mr. Baynes hit upon the idea of mounting the weights on arms projecting forward from the incidence control tube. Owing to the gearing between crank and wing, much smaller weights suffice to mass balance the wing.
   Of improved aerodynamic form, the fuselage has been considerably strengthened in the region of the cockpit. Otherwise it is generally similar to the previous Abbott-Baynes Pou.
   According to Mr. Appleby, the new machine is more stable, has a less severe stall, and is nicer to handle in every sense. This can well be believed after seeing his demonstration at Heston last week. Full control is available at 40 m.p.h.

CANTILEVER POU
Garden Engine: 30 h.p.

   Span 22 ft,
   Length 12 ft.
   Weight, empty 327 lb.
   Weight, loaded 550 lb.
   Top speed 80 m.p.h.
   Cruising speed 70 m.p.h.
   Take-off run 100 yd.
   Initial climb 400ft,/min
   Price complete ?108
   Makers: Abbott-Baynes Aircraft, Ltd., Farnham, Surrey.