The questions of perfection of the system of technical service and repair, economic and other measures, sent to providing and control of flightworthiness in the conditions of exploitation of aerotechics are examined in the presented article. To ensure the safe operation of existing equipment, the issue of its technical diagnosis with the purpose of determining the remaining service life is becoming more acute. Before proceeding to the forecasting of the residual resource, an analysis should be made of the main causes of accidents and failures in the technical systems of aviation equipment, the distribution of defects in the elements of the design of aviation equipment, the examination of the parameters of defects in order to assess the potential hazards and prioritize repairs detected in the diagnosis of defects, which in turn The choice of the diagnostic system influences. At presence of vagueness of decision-making apply the special methods, taking into account probabilistic nature of events. They allow to appoint the border of the field of admittance of parameter or necessary number of experiments for a decision-making about diagnosticating. solution of task of increase of authenticity of estimation of the state of equipment is offered on the basis of criterion of optimality with the use of Bayes 's method. To that end the high-quality indexes of diagnosticating are certain on condition of presence disrepairs, being corresponding conditional probabilities of the correct diagnosticating, and like by conditional probabilities of admission of disrepair and probability of false alarm. Will put every erroneous decision in accordance some price – cost of error. For faultless decisions this cost will arrange to consider equal to the zero. Then the system of diagnosticating can be characterized by expected value of cost of erroneous decisions. If   two systems of diagnosticating are compared, where first from them is optimal, then by virtue of the offered solution the optimal system of diagnosticating gives the least probability of admission of disrepair among all systems of diagnosticating, which conditional probability of false alarm is no more, than at optimal.

diagnostics, fault, optimality criterion, the average risk probability

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