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Pilot reports that twice in two weeks; attempted dc battery starts of apus had failed on B737NG aircraft. APU start capability becomes critical in the air if a dual engine failure occurs. Maintenance bite tests of apus after battery start failures indicate 'battery' fault. Apus start ok using ground power.
| Attributes | |
| ACN | 1164700 |
| Time | |
| Date | 201404 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B737 Next Generation Undifferentiated |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Parked |
| Component | |
| Aircraft Component | APU Controls |
| Person 1 | |
| Function | Captain |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical |
Narrative:
Twice in two weeks I've found myself attempting battery APU starts in B737NG. Neither one of them worked. Turns out there is an aircraft and dc [battery] APU start circuit in the newer model aircraft. Either one is deferrable; but none were written up or deferred at the time. Once we put [ground] AC power on the aircraft; the APU started and ran fine. I guess my question is that most of our APU starts are with AC power; and we don't have many opportunities to 'try' the dc APU start. The dc part of the APU start could be vital [if dual engine flameouts occur.] does maintenance check this with any regularity? Is this dc portion failure a 'trend' we need to check? (Maybe I just got lucky with 2 recent aircraft.) explore this as a failure trend that needs to be corrected. APU battery start in next generation aircraft.
Original NASA ASRS Text
Title: Pilot reports that twice in two weeks; attempted DC Battery starts of APUs had failed on B737NG aircraft. APU Start capability becomes critical in the air if a dual engine failure occurs. Maintenance BITE Tests of APUs after Battery start failures indicate 'Battery' fault. APUs start OK using Ground Power.
Narrative: Twice in two weeks I've found myself attempting Battery APU starts in B737NG. Neither one of them worked. Turns out there is an Aircraft and DC [Battery] APU Start circuit in the newer model aircraft. Either one is deferrable; but none were written up or deferred at the time. Once we put [Ground] AC power on the aircraft; the APU started and ran fine. I guess my question is that most of our APU starts are with AC power; and we don't have many opportunities to 'try' the DC APU start. The DC part of the APU start could be vital [if dual engine flameouts occur.] Does Maintenance check this with any regularity? Is this DC portion failure a 'trend' we need to check? (Maybe I just got lucky with 2 recent aircraft.) Explore this as a failure trend that needs to be corrected. APU Battery start in Next Generation aircraft.
Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.