Technology Notebook ContentsEffective Date: 15 June 98
Free Air Temperature Calibration
The free air temperature system is calibrated in conjunction with airspeed systems calibration.
The equation for the free air temperature is
Where
Ta = Free air temperature - deg K
tic = Indicated temperature corrected for instrument error - deg K
Mc = Ca1ibrated Mach number
K = Temperature probe recovery factor
Free air temperature is recorded throughout the speed range at low and high altitudes. The free air temperature readings are corrected for instrument error and plotted versus calibrated Mach number squared. The curve of Indicated Free Air Temperature versus Mach number squared should produce a straight line, and when this curve is extrapolated to zero Mach number (squared), it should produce the free stream air ambient temperature Each series of constant altitude runs, performed through an air mass of a constant temperature, should produce similar curves.
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