Ref FAA PHAK 5-44 to 5-51 Mach number is a kind of true airspeed indication method, it makes relationship with local speed of sound (LSS). Mach number = True Airspeed / Local Speed of Sound (LSS) LSS = 39 x sq root of  Temperature (K) Note: C + 273 = K   By FAA book’s … Continue reading Mach number – Sonic, subsonic, transonic?