Originally Posted by
RandomPerson8008
To make crossing restrictions some crews are maintaining takeoff flaps and climbing at ~ V2 + 10 to 4000 on NADP 2 runways. Thrust reduction on NADP 2 is based on flaps reaching 5 (selected at V2 + 40) while takeoff flaps are 10 or 20 for the 747. So, thrust reduction is not happening until 4000 when the first crossing restriction is met, which can take more than 3 minutes in a 980,000 lb airplane on a 35C day.
I've been flying for a while and despite not being familiar with HKG, surely if climb gradient is an issue, you'd be flying NADP 1, not 2.
While technically it is true that thrust should be reduced with flap retraction, that's too much work for my little brain, and I prefer my capacity is to be used for something else, so we just let FMC and A/T do it at a specified level (we use 1500ft AAL). If climb gradient is an issue (fairly rarely on the 737), we can play around with thrust reduction and acceleration altitudes in the OPT to meet the SID requirements.
Keeping takeoff thrust (and probably full rated one at that) for 3 minutes routinely during normal takeoffs... I wouldn't want to be the one paying your mx bill, that's for sure.