After three glide flights in the X-1, he flew it to a speed of 0.85 Mach on his first powered flight on 29 August. He encountered severe buffeting and sudden nose-up and -down trim changes during his next six flights. Then, during his eighth flight on 10 Oct., he lost pitch control altogether, as a shock wave formed along the hingeline of the X-1’s elevator. He reached Mach 0.997 that day but, without pitch control, it would have been foolhardy to proceed. Fortunately, the X-1 had been designed with a moving horizontal tail and Capt Jack Ridley convinced Yeager that, by changing its angle of incidence in small increments, he could control the craft without having to rely on the elevator.