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Which variable is needed to calculate and obtain the TAS from the CAS?
  • A
  • B
  • C
    Compressibility and density.
  • D
    Compressibility and temperature.
To obtain TAS from CAS we need to correct for compressibility and get the EAS and then correct the EAS for density error to obtain the TAS.
The dynamic pressure is a function of airspeed and density of the air. The ASI being calibrated for ISA conditions, any other air density will indicate an erroneous airspeed on the ASI. For instance, density reduces with increasing altitude and the IAS, and thus EAS will become progressively lower than the TAS.

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