In this event, an A330 was on APU power getting ready for pushback from the gate. Very soon after push back started, the electrical power from the APU to the aircraft was disconnected reverting the aircraft to battery power only. (Note: published reports have stated the APU auto shutdown and could not be restarted by the crew. An examination of the Electronic Control Box (ECB) fault log file retrieved from the ECB by the repair vendor has confirmed that there was neither an auto shutdown of the APU or any failed attempts to restart the APU.)
When our two mechanics got to the flight deck, the flight crew reported to them that the APU had an auto shutdown and that the APU failed to restart. The mechanics performed a series of BITE checks via the MCDU maintenance pages and could not find any faults with the APU. They, then, proceeded to restart the APU and it started on the first attempt without hesitation.
iMore than a couple of hours after the first logbook page was filled out by the flight crew, the mechanics were given a new logbook write‐up for the same APU failure and unable to restart plus it contained a discrepancy for the batteries lasting only 3‐4 minutes and unable to communicate on VHF #1 after the aircraft lost battery power. The mechanics after consulting with MOC regarding the alleged battery failure were requested to perform two A330 AMM Tasks. One was a BITE Test of the BCL and the other was the Operational Test of the DC BAT BUS and DC ESS BUS Isolations. Both of hese tasks checked okay. The VHF #1 was also tested and it, too, checked okay. Maintenance cleared these reported discrepancies and closed out the log page without any deferrals except for the APU MEL from the previous log page.
When the replacement flight crew showed up in the flight deck, they started to perform an undocumented “aircraft battery drain test” and got the same results that the previous crew got at pushback – only 3‐5 minutes of battery power before the aircraft went dark. When this replacement flight crew was asked by maintenance personnel where this “test” was coming from, the mechanics were told by the flight crew that it did not come from any manual. However, they did say that they were told in flight training that the aircraft batteries needed to provide at least 30 minutes of power.