Aerospace Instrument-Making Annotation << Back АSSESSMENT OF THE RESOURCE STATE OF THE HYDRAULIC FLUID OF THE HYDRAULIC SYSTEM OF THE AIRCRAFT THROUGH CONTINUOUS MONITORING OF THE MAIN INDICATORS OF ITS QUALITY S.A. Shilin During operation, the hydraulic fluid undergoes gradual aging. To assess its resource state, it is proposed to continuously monitor the acid number trend during thermal exposure due to the operation of hydraulic units. The results of monitoring the temperature of the hydraulic fluid in the hydraulic unit circuit are used, as well as the experimental dependence of the acid number on the amount of heat transferred to the hydraulic fluid. Keywords: resource state of the hydraulic fluid, criteria for the quality of the hydraulic fluid, continuous monitoring of the hydraulic fluid quality. DOI: 10.25791/aviakosmos.6.2023.1344 Pp. 28-32.