This info about buses' "bumping up" the TO thrust is news to me and that is great info, thanks a bunch.
Take that "info" with a pinch of salt: it was definitely true of my previous airline's CFM-56 powered A319/320/321s, but may be different for other operators/engine types/Airbus models.
As far as climb thrust derate washout, on our B744s it is definitely tied in with altitude, however I could see that it might make sense to tie it in with Mach No. as well. Airliners typically climb at a fixed IAS for the first part of their climb, and as temperature normally drops with altitude this fixed IAS is equivalent to a higher and higher MN as the aircraft climbs: in essence the washout would still be tied in with altitude, albeit indirectly.
Sounds complicated, then again it is Airbus we're talking about...
(Airbus guys please don't shoot, I too flew Toulouse products for seven years
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