APU Cannot start in Flight in C-130 Technical Posted December 18, 2014 We have this aircraft with APU start normally on ground but unable to start in Flight. The APU intake door opened to 15 degrees, rpm goes to 30 percent but no rise in EGT. Failed air test thrice. In the course of fault isolation, we have changed out the no.2 aux touchdown relay, door control relay, door closed control relay, ignition unit, fuel control unit, and APU door actuator. Have anyone out there had this experience and know what is the problems. We have decided to change out the APU. But what if it happen again.