AVIATION IN FRANCE JOURDAIN. 151 



been divided into two schools, those who favor the system of gov- 

 erned longitudinal equilibrium and those who prefer automatic longi- 

 tudinal equilibrium. 



The school of governed equilibrium is made up of those who rely 

 upon the pilot of the machine to overcome by constant maneuvering 

 any movements out of the line of perfect balance. Take for instance 

 the pitching. This movement, forward or backward, so familiar on 

 shipboard would tend to make the machine shoot up or down. To 

 overcome this pitching a movable horizontal rudder is used. This 

 part of the apparatus is composed simply of a miniature reproduction 

 of the sustaining i^lane and is usually placed in front quite a distance 

 from the center of gravity. This plane is pivoted on an axis and can 

 be inclined at the will of the pilot. If the machine tends to pitch 

 downward, the pilot, by merely increasing the angle of the plane, 

 lifts the front part of the machine; the whole apparatus follows 

 this movement and assumes a horizontal position, which is the posi- 

 tion of equilibrium. 



To overcome rolling, the machines, even those whose longitudinal 

 balance is a governed one, generally have a certain arrangement 

 which we might call automatic, embodied in the angle made between 

 the two planes following the longitudinal axis of the machine. This 

 angle reduces to a certain extent the amplitude of the oscillation. To 

 overcome the rolling movement the aviator acts exactly as in the case 

 of pitching ; he inclines the wing on one side or on the other. He can 

 incline either the whole wing by warping it, or perhaps only a portion 

 of it, the tip of the wing only being made movable. The governing 

 motion is the same ; if the machine begins to fall to the right or to the 

 left, it is necessary only to give a greater inclination to the wing on the 

 side toward wdiich the aeroplane is falling in order that it may right 

 itself. 



To prevent unexpected veering, there is a tail in the form of a cross 

 which acts like the feathers of an arrow and insures true direction. 



A machine of governed equilibrium thus composed of a plane and 

 a system of motor propulsion and of an arrangement to avoid pitch- 

 ing, rolling, and veering can rise and maintain itself in the air, but 

 it is a dangerous machine. To follow the very happy expression of 

 M. Painleve, it is " a veritable thoroughbred of the air " which needs 

 a jockey with plenty of nerve. The principal examples of this type 

 are the Wright, the Bleriot, and the Robert Esnault-Pelterie ma- 

 chines. The Wright machine, however, although of governed equi- 

 librium, differs from the ideal type that I have just pictured in that 

 it is a biplane. 



The real difference between a monoplane and a biplane, and the 

 reason why some aviators prefer the latter to the former is because, 

 88292— SM 1908 11 



