Inlet is a critical component of aircraft propulsion system and accurate measurement of its flow coefficient is important in inlet wind tunnel experiments. Flow coefficient measurement investigations using Pitot tube inlet were carried out at free stream Mach number 4.5,5.0,6.0, respectively. Correction of flow coefficients in all kinds of cases were acquired by comparing the experimental values and theoretical values. The experimental results indicate that the difference compared with the theoretical values gradually rises up along with the increase in the incoming flow Mach number. According to the engineering experience in supersonic wind tunnel experiments, the temperature at measurement cross section is equal to the incoming flow total temperature. This hypothesis is also used in the current experiments. However, it is proved that this hypothesis is the main cause resulting in measurement bias by analyzing the deference between the two kinds of total temperature as mentioned above and the flow field distortion at measurement cross section. In hypersonic wind tunnel, the total temperature at measurement cross section is lower than that of the incoming flow because of the existence of heat transform on model wall surface. In order to increase the precision of the inlet flow coefficient measurement, the correction of total temperature is also required.
