Page:Aerial Flight - Volume 2 - Aerodonetics - Frederick Lanchester - 1908.djvu/379

Rh purposes of propulsion that according to the magnitude of the thrust transmitted to the machine the 'angle of recuperation' of the machine is diminished, and if the thrust be sufficient the machine will retain its natural velocity with a horizontal course or even an upwardly inclined course, and it will moreover automatically adapt itself to whatever thrust may be applied, so that the effect of an increased thrust is only to increase the velocity of the machine in quite a transitory manner, the final result, after the trochoidal oscillations due to the disturbance have settled down, being a change in the course of the machine in an upward direction."

"Thus, in order to effect a change in the course of the machine in a vertical plane. I operate on the propelling mechanism by either increasing or diminishing the supply of working fluid or by such other means as may be appropriate to the motor employed. I may in certain cases introduce a counter thrust, instead of operating on the motor mechanism, by erecting a small plane or other obstruction perpendicular to the direction of motion of the machine so as to cause it to take a downward course."

"When only a temporary change of direction is required, as when evading an obstacle, the tail-plane may be used with effect for vertical steering, but only within the limits of the safe velocity of the machine."