Dear Jim, You are right, I also had the external power unit connected. Like I said before, I was able to reproduce the CTD many times with the configurations mentioned above. I'll try to collect more data(maybe a video) to share with you. Should we keep talking here or can I reach you somewhere else? Regards, Gabriel Silva FAA MEI CFII CFI CPL IFR MEL SEL Types C-550 / C-650 / CL-30