INSTRUMENT FLIGHT RULES WORKBOOK
506. AIRSPEED CONVERSIONS
By correcting calibrated airspeed for temperature and pressure altitude, TRUE AIRSPEED can
be calculated. True airspeed calculations are also affected by a number of other variables.
However, adequate accuracy can be obtained by simply correcting for temperature and pressure
altitude. These corrections must be applied, as aircraft seldom fly at sea level on a standard day.
Prior to working the example problem, review the following facts:
CAS scale is numbered from 80 to 1000 knots.
Pressure altitude is numbered from 0 to 80,000 feet.
Temperature section indicates from -80 C. to +120 C.
TAS is numbered from 100 to 1000.
The temp bar rises as you rotate the top disc to the right.
Given: Calibrated airspeed = 250 knots
Pressure altitude = 12,500 feet
Indicated air temperature = -20 C.
Find: True airspeed
Set CAS over PA (Pressure Altitude)
Align cursor to intersect temperature at temperature bar.
Follow down the cursor and read TAS.
Answer: TAS = 288 KNOTS
CR-2 COMPUTER 5-7
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