Mooney: Yes, mostly the BS statements were towards CAs that need to reinvent the wheel. And primarily towards our training dept and how they teach things.

If I came off aggressive then my apologies too.

As for the topic at hand. We press the IAS/MACH bug button at FL280 because most usually for temperatures that are close to ISA, the point where 290IAS equals .74M is at FL280. It just happens to be that way, and since we climb at 290 and transition to .74 when the two marry each other to the TOC that's why there's this notion that it's a company thing to always transition from IAS to MACH at FL280. While in fact, the company just says climb at 290/.74 (or 250/.70 or 320/.7something that i don't remember) and doesnt specify where or when to press that button except in order to meet 290/.74 profile. I guess i'm nit picking about the wording...

As for reasons from captains. I have no problem what so ever with CA saying something to the effect of, i am more comfortable with X let's do it that way. No questions asked there, we know who is in charge and who'se name is on the line. But I have a major pet peve (read dislike) for people that tell me do it this way because it says it in the book, when clearly our books state something different... that to me is reinventing the wheel, micromanaging and doing it with sheer ignorance.

higney:

FL320 is an arbitary number, it is by no means a scientific altitude that predicates guarenteed transition at all. All I mentioned is, that our books call for a slow climb at 250/.70 and that these two usually marry eachother at *around* FL320.... do not get hanged on this number.

As for your question FL316.... I honestly do not know a good answer. If you have one, please share. If I had to venture/guess, I would think it had to do with two things. 1) An arbitary altitude that signifies where the high altitudes start on high weights, warm temperatures days and finer A/P functions are needed to avoid upset of the small buffet margins.
2) Again, a GUESS. They prolly demonstrated good fuel numbers on a 250/.70 climbs and for some average tempreture they determined FL316 to be the point where you transition from one to the other. All in order to demonstrate good fuel numbers on the sheets.... just like they based every performance number on 25%MAC.

All guesses.