Date: 201907
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Aircraft component: APU Electrical
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: General None Reported / Taken
Contributing factors: Aircraft; Company Policy; Human Factors
Primary problem: Ambiguous

Narrative: I am writing this after some stewing on this topic/incident and I am still unsure if this should have been a maintenance write up; however; I am sure that this is a situation warranting looking into. My intent is to shed light into a situation that occurred in aircraft on successive days. Yesterday we had landed; had normal APU start after clearing the runway and APU had been running. When we had reached our 2 minute engine shutdown; I shut down engine 2. The APU was up and running and showed electrical load prior to shutting down engine two; on the Electrical page. However; the load didn't seem to transfer and the ECAS screen filled with messages and we lost everything for a moment until engine 1 took over and EICAS messages cleared prior to reaching the gate. APU remained running and no issues continued. I talked with the oncoming Captain and in collaboration didn't see any reason for anything further since we had zero messages. Our collaboration was we were thinking I didn't let the APU run long enough for load transfer and secondary being a new Captain. Today in a different aircraft; APU again running for a while and pulled into the gate with both engines running. Electrical page shows APU full load on the electrical page shut down both engines and the same thing happened; however; this time while parked at the gate. Everything again resolved and all EICAS clear. I think nothing about it but mention it to a very educated and senior Captain; thinking maybe the APU hasn't been running long enough and it does this as a result; however now I am curious. I am still unsure if this is the result of the APU not running long enough before engine shut down or if this is a true maintenance issue. On a side note while reviewing the AOM about single engine taxi I also noticed that I may have violated a procedure in the AOM which states under CAUTIONS: Shall not be initiated until crossing all runways. Lessons learned would be write up everything and let maintenance determine the cause with their knowledge. Let the APU spool up for longer and verify in depth that it has reached full capacity. Continuously learn and continue to be willing to admit a mistake and always be willing to learn. Being a new captain I find myself seeking the wisdom of those senior to me; however it's important to verify then trust.




Synopsis: EMB-175 Captain reported problems with APU electrical load transfer.