My last post, (as some will have realised)
was deliberately over-dramatised.
The batteries areonly as good as their reliability and state of charge,
To pretend to oneself that they meet their functional requirements, is tobe in denial.. they have caused 50 aircraft to be grounded and god knows how many completed airframes to back-up at the factory out-door.
there have been at least 2 out-of fuel instances, plus the BA incident, plus the "Sully" incident, that i can recall in my lifetime. in commercial Pax-carrying Aviation.
Composite -structures have totally different Thermal properties to Aluminium Alloys... to have blind faith in a bunch of feckwits who designed wings that wouldn't fit. a faulty electrical system that can backfeed and flatten the second battery (if neither becomes incendiary in the interim!)...is naive in the extreme.
IMHO, they haven't had enough operating experience to really know if fuel-freezing /starvation will ever be an issue.
Prudence suggests one plans for a worst-case scenario and the multiple-backups are/ should be predicated on this
IF both main-engines fail to produce enough power (for whatever reason)
It's all in the lap of an unsafe, unreliable battery-system to start the APU
As it stands, that can't be assured, so I stand by my assertion that 2 holes line up. It cannot be denied there is a safety-critical weak link in the design...the American authorities themselves decided that grounding was more important than national pride.
As a matter of National Pride, the US Government will make sure Boeing survive this crisis...but it won't be due to the expertise of the current management of the company.