Gulfstream V / G500 / G550
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Aircraft Equipment Problem Critical
General Maintenance Action
Aircraft; Company Policy; Procedure
On several trips we noticed a 0% load from the AUX TRU (Transformer Rectifier Unit). There was no CAS message and synoptic page remained green throughout the flight. When we were able to compare to our other aircraft (same type); we noticed there was always a load greater than 0% indicated. Concerned; we asked our maintenance group if it was normal. We were told that there was a possible wiring issue and later a possible broken ground wire but that it was not an issue. This went on for a couple of weeks until it was written up. Much displeasure was displayed as this is apparently a difficult troubleshoot and fix. There is an AFM load limitation on the AUX TRU of 40% on the ground which we were unable to see since it didn't indicate. The primary purpose of the AUX TRU is to do what one of a Main or Essential TRU's do if they are to fail. The load readout is important. It is not an MEL item.Many pilots and maintenance techs were aware of this issue. Some say it was this way from delivery and it was just noticed. I think it may have broken recently. My concern is knowledge of the problem without it being addressed in a timely manner. The difficulty of the task or the inconvenience to the passengers should never be a concern when a potential safety item occurs.
G550 Captain reported an electric distribution anomaly that had not been promptly addressed.