Challenger 300
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC complied w / Automation / Advisory
Aircraft
On the previous days flying we had a right generator disconnect during APU startup in flight. The APU started normally and we reset the generator with no other indications noted. We discussed the glitch and decided to monitor and contact maintenance if we noticed any further problems. While on approach as I was completing the in range checklist I proceeded to start the APU prior to intercepting the final approach course. At about 50% APU RPM during start up the right generator disconnected. At about 80% APU RPM the left generator disconnected and we went to essential power. At this point we lost all four displays and the PF was flying off the standby instrument.Unsure what caused the event; but the result was a dark cockpit.We were IMC; but only about 500-800 ft prior to breaking out in MVFR (at worst). I immediately reset the right generator and it took up the load. The screens started to reset. My MFD and PFD had no information displayed and were attempting reset. I asked if the PF wanted vectors and he replied that he had navigation and I saw that he had green source available and was on course and glideslope. I then reset the left generator and it responded normally and connected. We ended up landing in normal configuration.If I were to redo this leg I would have started the APU well prior to intercepting the final approach course. I think that since the weather was not low IMC I may have been showing just a little complacency and was operating as if the IMC conditions were not as much of a concern. In IMC conditions don't try to save time on the APU. Get it started in plenty of time in case of just such an occurrence.
CL30 Captain reported both generators disconnected when the APU was started on final approach which caused the electrical system to go to essential power. Captain reported a reset of both generators and landed in normal configuration.