Design and Verification of Full Authority Digital Electronic Control System for APU

A hydro-mechanical control system (HMC) is adopted by the auxiliary power unit (APU) of certain helicopter, whose complex structure is difficult to be modified and realize sophisticated algorithms. As technology evolves, there is an urgent need to retrofit it to a digital electronic control system. . For digital control renovation for the auxiliary power unit, a full authority digital electronic control system (FADEC) is designed, key techniques of which are studied, such as overall structure, control laws, fuel system based on electric fuel pump. Functions, performances and key techniques of the FADEC system are evaluated on test rig, and the results show functions of control system are enhanced and performances of APU are improved remarkably under the control of the designed FADEC compared with the original hydro-mechanical control system.