PPRuNe Forums - View Single Post - 787 Batteries and Chargers - Part 1
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Old 9th Mar 2013, 13:13
  #899 (permalink)  
Join Date: Feb 2002
Location: UK
Age: 54
Posts: 2,686
So, what protects the APU if it catched fire during an auto-shutdown, with no personnel present? (Must emphasise this is not a 787-specific question.)
Usually the APUC stays powered for approx 2 mins after the APU shuts down. I think the 737-3/5/500 had problems with this early on as pilots/engs were shutting the battery off as soon as the APU started to shutdown. The consequence was that on the next APU start a failure would occur as the APUC was still in shutdown mode.

Back to the 787.
If Boeing insist on a battery that 'may' fail but it's 'safe' as it will be contained then the APU needs a seperate power source. IE A PMG that will continue to power the APUC/FADEC when the APU is up and running.

If the backup can't be relied upon then the backup needs a backup.

What a mess!
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