I’m asking because of the new HKG SID’s.
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.
A genx2b67 failed and this technique was blamed due to it staying in takeoff thrust for 3 minutes (even though it’s rated to stay in takeoff thrust for 5 minutes or 10 if an engine failure has occurred on another engine).