I am confused, t-bag. Addmitedly not knowing how 787 FMC speed schedule works, but at at the moment I am scratching my head around your description.
1) At FL370, a reasonable actual level for your scenario, M84 = 277 kt IAS.
2) ATC issued a speed reduction, and the FMS / crew (*) carried 0.84 in the descent, accelerating until reaching the crossover altitude.
3) At some point, your non-compliance become a concern and questions were raised as ATC can see the actual IAS. At that point, your IAS was probably being observed for quite some time already, before they spoke up.
a) In a perfect world, the ATC would have said just "reduce speed 250 kts", as your IAS was already higher - opposite from the typical crossover sceanrio.
b) A perfect pilot (quarterback's), in a situation similar to the originally described, could have said:
- reducing 250 kt now, or
- unable, minimum clean 2xx kts [where it is more than 250]
- roger, 250 kts as soon as we can. [min Mach restricted]
I wonder if 787 falls into the 3rd option?
Last edited by FlightDetent; 22nd Jun 2017 at 13:42.