FIELD: aeronautical engineering. SUBSTANCE: helicopter primary gearbox has two joint units for connecting the shaft of engine free turbine with input shaft of main gearbox with support of each engine to housing of gearbox. Two symmetrical kinematic chains consists of overrunning clutch, taper and cylindrical stages. Drive wheels are located in line with cylindrical wheel whose rim is mounted on supports and hub is made for axial and redial displacement relative to toothed rim. Lower support of shaft of lower main rotor and upper support of shaft of upper main rotor are made in form of radial-thrust bearings. Attachment points for securing the primary gearbox to fuselage are made in one plane on housing of primary gearbox. Gearbox consists of two parts between which attachment point of helicopter main rotor control unit is arranged. EFFECT: simplified construction of helicopter primary gearbox, enhanced reliability and increased service life. 4 dwg
