Originally Posted by
jbcarioca
None. The FAA, in the document that I linked as well as a number of others, provides statistical definitions for each of these terms. "Probable" in English, is defined by them as "likely to happen at least once in the lifetime of a given aircraft" (BTW, that is memory, I did not go back to read the exact words. By definition 'probable' events that the FAA allows are minor ones. If an event that should be more rare proves not to be there is prima facie evidence of a serious problem. Such events may trigger certification reviews (one of those produced the modern type rating system) or a variety of slightly lesser actions. They also can trigger emergency groundings as in the cases of the B787 now and the DC-10 in 1979.
I hope that helps. If not we can start a thread for FAA-specific terms, definitions and uses. As a general rule those are useful only to manufacturers, fleet operators and anal-compulsive people.
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.
Originally Posted by
mitchmu
One solution to that problem is to replace the Lithium Ion batteries with old style NiCad batteries. If done properly, then fire risk on 787 should fall to the level accepted on all existing aircraft. Right?
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.