It is well known that the upper-air temperature recorded by a thermometer installed on an aeroplane is a little higher than the actual temperature. W. Findeisen discussed the correction from a theoretical point of view. We have undertaken to determine the correction by rotating the thermometer. Our preliminarily obtained result is as follows:
Δθ=2.4×10^-5u²°C, u: speed in km/hour. The final determination of the factor is postponed for future investigation.