Originally Posted by
RandomPerson8008
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).
why do you have to do that .It is not mandatory.Your choice for normal nadp 1 or 2 .If you can’t cross that altitude you have to tell ATC for alternate procedures or other runways. If altitude is 10000 feet then you have to maintain V2+10 and TOGA thrust until reaching 10000 feet?
HKG SID requires 4000 and speed at 210 kt because of TERRAIN not NADP .In this situation you have to choose which NADP is practical,1 or 2 , normally 1 is suitable.Ok if you choose NADP 2 the acceleration is initiated at normal altitude to 210kt and thrust reduction is initiated at any point along acceleration segment even the first flap is not retracted.(In normal routine the easy way to do that is to select the next flap in take off ref page for thrust reduction and thrust is not reduced in this case) . Anyway if this SID is not practical , choose other SIDs or other RWs .No such NADP as you said in the world.