The other day (during a particularly uneventful flight) I was looking at the flight plan and in particular the TC and TD entries. It made me wonder what rates of climb and rates of descent the FMC uses to calculate such flight plan entries. Does anyone know? I had a quick skim through the manual but did not spot anything referencing this, or did I miss it? A quick calculation for the step climb changes yielded a rate of climb of 700 but not sure how accurate this is. Regards Stuart

what rates of climb and rates of descent the FMC uses to calculate such flight plan entries.

 

I think it's whatever is economical to meet CI/RTA/speed/altitude requirements. Your climb rate is going to be high if you are lightly loaded and not facing any altitude/speed constraints.