On the Stability of la Cierva’s Autogiro

In this paper, we rediscover in detail a series of unknown attempts that some Spanish mathematicians carried out in the 1930s to address a challenge posed by Mr. la Cierva in 1934, which consisted of mathematically justifying the stability of la Cierva’s autogiro, the first practical use of the direct-lift rotary wing and one of the first helicopter type aircraft.