The research objective was the establishment the opti-mum operational parameters and operating modes of soil-cultivating MTA in structure with the tractor equipped with the engine of constant power by means of theoretical techniques. The main objective of the research was by means of universal settlement technique to set optimum parameters and operat-ing modes of soil-cultivating unit with the tractor of the 5th class of draft on which the engine of constant power is in-stalled. As the object of the researches the tractor of the 5th class of draft of John Deere 8310R when performing the op-eration of plowing with PLN-8-35 plow was considered. The settlement technique of establishment of values of power and technical and economic parameters of the work of MTA based on the method of functions of casual arguments was used. By the results of the research it was established that engine ca-pacity at variation coefficient = 0.2 would decrease by 7.5 % in power maximum zone, according to the bench characteris-tic, specific fuel consumption would increase by 1.5 %. The calculation of average values of frequency of rotation of cranked shaft showed that they also decreased (by 7.5 % at the value к Н м). It led to the decrease in work-ing speeds and the productivity of the unit. According to the calculations of value of optimum load modes of the engine for criterion of maximum of effective power correspond to value of the torque к Н м. It is the area of the maxi-mum power of the bench characteristic of the diesel. The main result of the researches was on the example of MTA which part were John Deere 8310R tractor and the plow of PLN-8-35, the indicators of the efficiency of using the units of this kind under production conditions were considered. For the purpose of more effective use of tractors with engines of constant power on the basis of settlement techniques the operational modes of working course of soil-cultivating units for the main groups of technological operations were proved.