Originally Posted by
mduell
Sorry I was unclear - I understand the definitions in the advisory circular. I was wondering what the original source for the 50000 flight hours was. I've seen it a lot of places, but the first place I saw seemed like the 50k was a guess.
Assuming the battery chemistry is the problem. Recall that NiCds are also subject to thermal runaway, and have had thermal runaway incidents on aircraft before.
The 50,000 hours are Boeings estimate to flight hours since certification IIRC. Thus the incidents per 50,0000 hours/
The NiCad incidence is very, very low. Look it up.