# How does the pitching moment change as the speed of A/C approaches critical Mach number?

In an aircraft performance course, I saw that pitching moment goes backwards as the speed of A/C approaches critical Mach number. In fact, that results in nose down pitching moment. But, according to my notes, there must be shock waves at the back of the A/C. In this situation, should not these waves behave as force pitching down? How can it be possible? And why?

• @mins yes that was exactly what I meant – Volkan Aydıngül Mar 30 '17 at 7:08