One of the most important parameters specifying the usability of the miniaturised electrohydraulic servomechanism includes a static friction degree in its slide pairs, i.e. resistance of the slider’s movement from rest after some time of its staying at rest under pressure. Therefore, at the stage of designing and construction of the electrohydraulic servomechanism, it is important to determine the greatest static friction degree, which may arise in the slider hydraulic pair of this device during its operation. The objective of this article is to present a method for estimating the maximum static friction values in the slide pair based on the extreme value theory. The operation and loading conditions of the slide pair of the electrohydraulic servomechanism for the unmanned aircraft control system were described. The procedure for estimating the maximum static friction degree in the slide pair with the use of the extreme and probabilistic grid was presented. The extreme and probabilistic grid structure was based on the Gumbel probability graph. The graphic presentation of results of the static friction experimental studies in the slide pair on the extreme and probabilistic grid was discussed. By using the graphics method, the empirical dependence of the static friction force in the slide pair on the working fluid pressure in the hydraulic drive (loading conditions) was determined. A practical example of estimating the maximum values of the static friction force that may occur in the slider hydraulic pair of the miniaturized electrohydraulic servomechanism is shown.