About the difference in the indications of the true air speed by the mechanical index and the air signal system

Reliable information about the altitude and speed parameters of an aircraft (AC) is required to improve the safety and efficiency of flight missions. In this regard, the task of studying the features and improving the characteristics of existing meters of these parameters is quite relevant. Purpose of the study. The problem of estimating the difference between the readings of the true airspeed of an aircraft by a mechanical indicator and an air signal system (ASS) is considered. Materials and methods. Methods for measuring true airspeed used on modern aircraft are analyzed. It has been established that, despite the availability of the latest developments, SHS, operating in a set with air pressure and stagnation temperature receivers, as well as angle of attack and slip sensors, is currently the most common true airspeed meter. Mechanical indicators are also used, which are included in the composition of the combined speed indicators (KUS). In accordance with the physics of the phenomena that take place during flight, in order to calculate the true airspeed, it is necessary to know the air temperature at the flight altitude. In SHS, this temperature is determined from the measured stagnation temperature. There are no temperature meters in the composition of the KUSs, their design is based on the dependence of temperature on pressure, which takes place for the international standard atmosphere. It is clear that this leads to the appearance of a methodological measurement error. Results. A formula has been obtained that makes it possible to determine the difference in the readings of a mechanical indicator and SHS. It is shown that this difference is a function of the stagnation temperature (outside air temperature), total and static pressures at flight altitude. Numerical studies have been carried out to estimate the quantitative discrepancy between the readings. It has been established that the difference in readings can reach several tens of m/s under operating conditions, which is quite significant. Conclusion. The results obtained can be used in the operation of the aircraft, as well as in improving the algorithmic support of the onboard digital computer system, which is the central link of the flight and navigation complex.