Nav Computer: In AIRSPEED
window put temperature (-15ºC) next to MachNo
Index.
Go to TAS (250kts) on
inner scale and read Mach number next to it on the outer scale: MN 0.4.
Calculator: MN =
TAS/LSS = 250/38.94 √ (273 – 15) = 250/38.94x √258
= 250/38.94x16.06 =
250/625.5 = 0.4