Dash 8-300
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Company Policy; Procedure; Equipment / Tooling
Upon arriving at the aircraft [for the]first flight of the day; there was no GPU [Ground Power Unit] present. I heard several explanations as to why but I was assured that when a GPU became available; it would be brought over for our use. In an effort to keep the flight on schedule I applied battery power to the aircraft in order for the Flight Attendant to begin preflight of the cabin. Once battery voltage reached 22 Volts; I powered the aircraft down and we continued to wait for a GPU. Ramp personnel brought over what appeared to be an AC GPU with a rectifier device to convert the power to 28V DC. This device was plugged into the External DC receptacle on the nose of the aircraft (the rear External AC receptacle was at no point utilized). Voltage on the Right Main DC Bus was observed to be approximately 25.5V with External Power applied. Following two normal engine starts using GPU power; I signaled for the GPU to be disconnected. The First Officer and myself then observed the '#1 DC GEN HOT' light illuminate. At this point we had not yet begun push back and were still at the gate with the propellers in feather. After following the checklist procedure and discussion with maintenance control we turned the #1 DC generator off allowing it to cool and then turned it back on. Although this initially appeared to correct the problem; the '#1 DC GEN HOT' caution re-illuminated and after discussion with Maintenance Control and contract maintenance; we determined it was safe to ferry the aircraft for repair.
For an unknown reason; the aircraft experienced a DC generator overheat fault following the use of an AC Ground power unit with a DC rectifier to provide aircraft power at the gate.