Appendix I
Theory of Stability—Pénaud, 1870
In § 65 reference has been made to the work of Mons. Penaud in connection with the stability and equilibrium of his flying models, and in particular to an argument advanced by him touching the theory of longitudinal stability.
In an article by him published in "L'Aéronaut" tome v., p. 2. Mons. Penaud not only describes two types of flight model, a "hélicoptère" and an aerodrome (the latter already given in Figs. 9 and 10), but gives also a full statement of his views of the theory of automatic stability. The author feels that, in spite of the rather inadequate nature of the explanation which Penaud was able to offer, the matter is of sufficient historical interest to demand its being quoted in extenso. Whatever faults may exist in Penaud's theory, this much is certain: the man himself had a clear understanding that an aerodrome could be made possessing complete stability within itself, without any adventitious aid in the way of equilibrating devices, a fact that since his time has been almost forgotten.
The portion of Mons. Penaud's article that has been thought worthy of reproduction is as follows:—
"Après avoir varié de toutes façons les proportions de mon hélicoptère ; après l'avoir vu voler sur place, planer obliquement, s'élever comme un trait, la pensée me vint tout naturellement d'appliquer mon méchanisme à la propulsion d'un appareil du genre aéroplane, de façon à montrer la possibilité de ce système comme l'hélicoptère démontrait la puissance
350
