from the above mentioned site...
There has been much written and said about this incident by parties outside of the maintenance organization. Many members of the company have requested more facts about this incident particularly regarding maintenance’s role. The purpose of this memo is to explain why the aircraft did what it did, to communicate that the aircraft worked as designed,and to reiterate that our maintenance team handled the situation extremely well and ensured safety of flight.
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.) Within 5 minutes of the APU being hutdown, the aircraft went dark. The jet bridge was re‐attached to the aircraft and ground power was re‐connected to the aircraft.
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. After it started, the mechanics told the flight crew that in their assessment the APU was in serviceable condition and they were okay to sign it off however, they needed the crew to complete a log book entry with their discrepancies. That is when the crew pushed back saying that they did not feel comfortable with the status of the APU and that they wanted it “fixed.” The mechanics then gave the crew another option to have the APU deferred on an MEL. After some continued conversation with the flight crew, the flight crew finally elected to have the APU MEL’ed so hey completed a log book write‐up for “APU failed at gate, unable to restart.” The mechanics removed the logbook after the log page was completed by the flight crew so that they could complete the MEL deferral for the APU. More 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. Maintenance later learned that the original flight crew was being replaced as they did not feel comfortable with the aircraft particularly with the APU being on MEL and the aircraft batteries only providing 3‐4 minutes of power to the aircraft on the ground. It should be noted that at no time did maintenance personnel pressure the crew into taking the ircraft. They did explain the limitation of the APU being on MEL which was that the aircraft would be limited to 120minute ETOPS. But, they did not question the Captain’s authority to refuse the MEL. uring the transition from the original flight crew to the replacement flight crew, maintenance personnel did clear the APU MEL after the ECB was replaced. 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. Maintenance observed this “test” being done again and witnessed the same results. After further consultation with MOC to confirm that there are no battery drain tests in the AMM, the aircraft batteries were changed as a precautionary measure. The “test” was performed again with the fresh batteries and the aircraft remained powered for 30 minutes. It should be noted that the aircraft at this time was not in a flight configuration, as previously “tested”, meaning the electrical draw on the DC ESS and AC ESS buses was less. The replacement crew, then, told maintenance that they were okay taking the aircraft as is; however, since the ETOPS Check had expired, a new ETOPS Check was required to be ompleted. After the ETOPS check was completed and the passengers were re‐boarded, the flight left almost 11 hours late. It should be noted that the ECB that was removed to clear the APU MEL came back from the repair vendor as No Faults ound. Also, both batteries were returned from the battery vendor after inspection with no corrective actions needed on either battery. n summary, our entire team handled this situation extremely well. They thoroughly reviewed each FDML write‐up, took very precaution to ensure they were addressed, and delivered a safe and airworthy aircraft to the flight crew.
Technical Clarification: One technical issue raised during this event that Maintenance could not quickly explain was why the aircraft batteries only provided power for less than 5 minutes. Detailed below is a technical clarification on that issue:
In this situation, with an A330 on the ground with no AC power available (No Integrated Drive Generator (IDG), Auxiliary Power Unit (APU), or ground power), BAT1 and BAT2 will power the DC BAT, DC ESSENTIAL, and AC ESSENTIAL buses when the BAT pushbutton switches are in AUTO. The DC ESSENTIAL SHED bus is disconnected when on battery power only. Once one of the battery voltages drops below 23V for 16 seconds and the LGCIU detects the nose landing gear downlocked and compressed; the Battery Charge Limiters (BCLs) will disconnect both batteries from the DC BAT, DC ESSENTIAL, and AC ESSENTIAL buses. This is done to prevent completely discharging the batteries while the aircraft is on the ground (Reference AMM 24‐38‐00). When the BCL disconnects the batteries from the DC ESSENTIAL us, the VHF 1 radio become unavailable. To reconnect the contactors, the flight crew must switch the BAT push button switch to OFF, then AUTO. This would restore the VHF 1 radio. (Reference ‐ USA A330 Controls & Indications Manual) The amount of time the batteries will power these buses will be dependent on the capacity of the batteries and the lectrical load they are holding. The nominal capacity of an A330 battery is either 37 Amp‐Hour or 40 Amp‐Hour,
depending on the battery part number. In the air, the AC and DC buses will be supplied by the IDGs and if running, the APU. If both IDGs and the APU become unavailable, the Constant Speed Motor/Generator (CSM/G) will supply the AC and DC buses. The CSM/G is powered by the green hydraulic system as pressurized by the engine driven hydraulic pumps or the Ram Air Turbine (RAT) should power be lost in both engines. If the CSM/G is unavailable then the aircraft batteries will power the DC BAT, DC ESSENTIAL, and AC ESSENTIAL buses. The BCLs will not disconnect the batteries when one is discharged below 23V; hey will continue to power the hot battery buses, DC BAT bus, DC ESSENTIAL bus, and the AC ESSENTIAL bus as long as possible.
There was some discussion during this event that the aircraft batteries must provide at least 30 minutes of power as the aircraft was certified to that. To clarify that point, the A330 is certified to provide battery power to the DC BAT, DC ESSENTIAL, and AC ESSENTIAL buses for at least 21 ½ minutes while in flight. There is no certification requirement for how long the batteries need to power the A/C on the Ground before the BCLs disconnect the Batteries.