The article examines a method of obtaining the required initial data for adequate mathematical modelling of nonstationary processes in the Mi-8MTV helicopter computer and flight simulators. The principle of the method is as follows: the video fixation of non-stationary modes of the power plant operation in a real flight and the computation of the obtained dependencies according to the known formulas of mechanics, aerodynamics, the theory of gas turbine aircraft engines, etc. are analysed. Moreover, by juxtaposing the computed dependencies and the obtained video fixation, the parameter values, that determine the helicopter power plant behaviour (the inertia moment of the helicopter main rotor system, etc.) in the non-stationary modes, are found. These parameters allow us to solve the problem by modelling a complete picture of the helicopter power plant behaviour in abnormal and emergency situations, under which, it is impossible to formulate an objective verdict without violating flight safety requirements. Given the circumstances, the feasibility of an advantageous and reliable solution to the problem is considered using mathematical modelling of the transient power plant operation modes both in non-stationary conditions and in abnormal and emergency situations. A simulation of these scenarios and responsive actions is carried out using helicopter simulators. In a real flight, a helicopter crew monitors the functional systems status and the development of abnormal and emergency situations relying on readings from dial instruments, digital indicators, annunciators, and other computer-aided facilities in the cockpit, not only by the parameter values, but also by dynamics of their variation in flight. Within this timespan, the pilot must assess an abnormal situation and decide on required actions.