Refer to figure.
Note: FL065 represents the pressure altitude of 6500 ft, expressed as a flight level. This altitude is required when converting the Rectified Airspeed (RAS) to True Airspeed (TAS).

We can use a flight computer (CRP-5) to calculate the TAS once the pressure altitude and the actual OAT are known.
1. Calculate the actual OAT

• The lapse rate at which temperature decreases is approximately 2°C/1000 ft up to 36 080 ft (tropopause)
• ISA temperature at 6500 ft: +15°C – (2°C x 6.5) = +2°C
• Hence, OAT at 6500 ft: ISA temp + ISA dev = +2°C + 15°C = +17°C

2. Calculate the True Airspeed (TAS)

1. In the AIR SPEED window, align +17°C with 6500 ft (pressure altitude).
2. Align the cursor with RAS 84 kt on the inner scale and read TAS 95 kt on the outer scale.