Converting Mach Number to True Airspeed
To convert Mach Number to True Airspeed (or vice versa), rotate the inner dial until you see the Mach No. Index inside the airspeed correction window on the inner dial. Line up the true or outside air tem- perature (do not use Indicated Air Temperature) opposite this Mach No. Index. Mach Number on the inner scale reads opposite True Airspeed (in nautical miles per hour) on the outer scale. In Figure 14, at an outside air temperature of +15°C and Mach 1 (10 on the inner scale), read 661 knots on the outer scale.
Figure 14
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