Thanks for you reply alatriste,
So in a sense what is says is if you have an actual TOW of 63t
you should calculate the performance for a weight of 66.2t (66.15)?!
What if your actual is already at max? 72.5t. Then what?
(Probably not alot of flex left in the engines but anyway).
So, is this document still valid or was it lost in the Boeing merger?
Also, if one wanted to be a stickler for word interpretation. The only "real" derating on the MD is the ART system.
The assumed temperature is not a derate in itself, or so I was told by a performance engineer. But I'm sure that was not what MDC meant.