Flight, June 1923
THE MIGNET LIGHT 'PLANE
An Unorthodox French Machine
AN experimental light 'plane of unorthodox design has just been completed in France by an amateur designer and constructor, M. Henri Mignet, and is now at the Orly aerodrome awaiting
its first flying tests. M. Mignet, who has built the machine himself, is a great admirer and student of bird flight, and he has come to the conclusion that the apparently very complicated movements of which birds are capable can be reduced to a few relatively simple principles, capable of being translated into structures of more or less usual form, and presenting no great engineering problems. His first light 'plane, which we are able to illustrate and describe this week by the courtesy of our excellent French contemporary Les Ailes, was designed and built with a view of imitating the bird in so far as the designer has been able to follow the problem. This applies to the manoeuvres of a bird in gliding flight only, and no attempt has been made to imitate the flapping wings.
Briefly, the main feature which M. Mignet has sought to incorporate in his design is the avoidance of what he considers to be the greatest danger of the ordinary aeroplane, i.e., the perte de vitesse, or stalling. He considers that the safety of a bird is due to its capacity for flying in the stalled attitude, made possible by very effective controls. The keynote of the Mignet light 'plane is, therefore, controllability. While we agree with the designer in his estimate of the problem, we cannot say we feel convinced that he has attacked the solution in the right way.
From the accompanying illustrations it will be seen that the Mignet light 'plane is a parasol monoplane without vertical fin or rudder, but with very large ailerons and a tail showing a very pronounced dihedral. The most remarkable feature of the machine, apart from the absence of vertical tail surfaces, is that the entire tail, which is of lifting section, is not adjustable for incidence, although it can be rocked around a longitudinal axis. M. Mignet has come to the conclusion that a bird does not use its tail as an elevator, but merely as a rudder for steering in a horizontal plane. As the difficulties of imitating the warping tail of a bird were considerable, M. Mignet has attempted to obtain the same results by giving the tail a pronounced dihedral and hinging it around a longitudinal axis. The action of this type of tail (which, as already stated, is of lifting section) appears to be that for turning to the left the left-hand side of the tail is raised and the right-hand side depressed. The designer is of the opinion that this disposition of tail will prevent a machine from spinning, as, when tilted, the lifting tail is more effective than a rudder and fin. Practical experience alone can show whether or not M. Mignet is right. Personally we think that there is considerable doubt as to the value of such a tail, nor are we quite sure that, with the large ailerons working together as elevators, a tail elevator will not be required. At any rate, the experiment is certainly interesting, and we trust the first test flights may be carried out without accident. If the test pilot goes to work steadily and step by step, there should be no great danger, and certainly this particular use of a light 'plane, i.e., for research purposes on a man-carrying scale and in free flight, is one of the most important to which it can be put, offering a method of convincing demonstration at relatively low cost.
The wing of the Mignet is of a modified Gottingen No. 426 section, and the ailerons form close on one-half of the entire wing surface. They are so interconnected that when the control stick is held central and moved fore and aft, the two ailerons are raised and lowered together, while lateral movement of the stick gives them a differential movement, exactly as in the Fairey patented system. Mr. Fairey has found, however, that it is necessary to use a tail plane of unusual section, and linked up to the controls in such a way as to alter its incidence in conjunction with the wing flaps. That is why we rather doubt the effectiveness of the rocking tail of the Mignet.
Constructionally the wing is of usual type, the centre supported on a cabane from the fuselage, and the wing braced by a single strut on each side. Hinges on the rear spar permit of folding the wings, and the large chord of the ailerons, coupled with the fact that these can move up or down together, enables the overall width when folded to be kept down to a very low figure. In large and heavy machines like the Fairey types, the flaps are, of course, connected up to a special gear for variation of camber. In the Mignet light 'plane this has not been considered necessary, and the flaps are connected to the joystick direct, the pilot working them with the stick both for lateral control and for variation in camber. In this manner it is thought that he will be better able to "feel" the machine.
The fuselage is of normal construction and rectangular section. The pilot's cockpit appears to be too far aft, even allowing for a lifting tail, and one would expect the machine to be tail heavy, especially in view of the small weight of the engine. The latter is a 10 h.p. Anzani cycle-car engine, with two horizontally opposed air-cooled cylinders. A two-bladed propeller is driven direct, and the petrol is contained in a tank in the centre of the wing, giving direct gravity feed.
The undercarriage consists of two wheels, placed, it would appear, rather too far forward, mounted on axles from the bottom of the fuselage and sprung by telescopic struts and springs to the top of the fuselage. A third wheel, partly housed in the fuselage, takes the place of the more usual tail skid.
The Mignet is purely an experiment to try out the designer's theories, and its trials will be watched with interest. Following are the main characteristics of the machine: Length, o.a., 5 ms. (16 ft. 5 ins.); span, 6-5 ms. (21 ft. 4 ins.); area, 13-3 sq. ms. (143 sq. ft.); width with wings folded, 2 ms. (6 ft. 6 ins.); weight empty, 125 kgs. (275 lbs.; weight of pilot, 70 kgs. (154 lbs.); weight of fuel, 18 kgs. (40 lbs.); total loaded weight, 213 kgs. (469 lbs.); wing loading, 3-3 lbs./sq. ft.; Power loading, 47 lbs./h.p.