TO THE QUESTION OF DETERMINING THE BAROMETRIC HEIGHT BY A MECHANICAL ALTIMETER AND AIR SIGNAL SYSTEM

Abstract

Reliable information on the altitude and speed parameters of the aircraft (AC) is required for safety and increasing the efficiency of flight missions. In this regard, the task of studying the features and improving the characteristics of existing meters for these parameters is quite urgent. Purpose of the study. The features of determining the barometric altitude of an aircraft by a mechanical indicator and an air signal system (SHS) are considered. Materials and methods. The essence of the baro­metric method for measuring the altitude of the aircraft is analyzed, it is found that to build a clear theory of the method, it is necessary to know the dependence of the temperature of the atmosphere on the altitude. Moreover, it is known that this temperature usually decreases with increasing altitude. However, the rate of decrease unpredictably changes both at different times of the year and day, and at different points and at different heights. Moreover, in some cases, in a certain range of heights, the temperature may not decrease, but, on the contrary, increase. In this regard, there is some problem with the formalization of this dependence. When constructing a theory of the method for mechanical pointers, one proceeds in such a way that the dependence for the International Stan­dard Atmosphere (ISA) is used, in which temperature and pressure are uniquely related. When developing algorithmic support for SHS, it is considered that the temperature decreases with height as well as in a standard atmosphere, but its actual value at the level of the reference plane can be anything that is not at all related to pressure and altitude in ISA. For this purpose, a temperature control unit is provided in the SHS at the level of the height reference plane. Results. A formula has been obtained that makes it possible to determine the difference between the readings of a mechanical altimeter and SHS. It was found that this difference is a function of pressure and temperature at the level of the plane of the altitude reference plane, as well as the actual pressure at the flight altitude. Numerical studies have been carried out to assess the discrepancy between the readings. It has been established that the relative difference in readings can reach the order of magnitude under ope­rating conditions, and it practically does not depend on the aircraft altitude and is, in essence, a constant for the indicated initial values of pressure and temperature (at the level of the plane of the altitude reference). Conclusion. The developed algorithms can be used to improve the algorithmic support of the SHS.