Based on the research of the development and the maturity of turbo-shaft engine's control systems abroad

a control system scheme including a hydromechanical system as the backup was proposed. The module of backup hydromechanical control system could work synchronously with the digital control module

and switch to the main control system smoothly in case of failure of the digital control mode. This kind of design could achieve the function of backup control for the fuel and the compressor guide vane

and also guarantee the security for the engine's work and the return of helicopters. The design has been checked with the semi-physical simulation experiment and engine rig test after design and manufacturing. According to the verification result

the system has a control precision of ±0.5% for power turbin speed and precision of 4° for the guide vane

which insures the well application in engineering.