@FASRP
Peterwe's method of analysis is valid (I haven't checked the numbers) if you assume a constant failure rate, which is typical in mid-life of most objects subject to failure - including people.
The failure rate typically follows a "bathtub curve" with a high initial failure rate, a constant and (hopefully) low rate in mid-life, and then another increase due to old age.
The initial failures are normally screened off by factory stress testing or burn-in - one would hope that the parts Boeing are using have been sufficiently screened. The old-age failures would be avoided by mandating replacement before the bathtub curve starts rising.
From a reliability point of view, what we're seeing with these batteries is either an unexpectedly long infant mortality period, an elevated mid-life failure rate, or a premature ageing: we don't have the numbers to plot the graph and determine which, but Boeing certainly does, and has probably covered these bases with the proposed actions (the other two that don't get much mention here, not the containment vessel which is there just to keep the FAA happy).
Last edited by fizz57; 24th Mar 2013 at 18:15.