There is
no ICAO NADP time limit for takeoff thrust. NADP is defined by
altitude, not time: the first action (thrust reduction or acceleration) is at
≥ 800 ft AAL and the noise abatement procedure is
usually completed by
~3,000 ft AAL (guidance, not a limit).
For both NADP 1 and 2 the first action is at 800 ft and the procedure is completed by 3,000 ft, with no time-based requirement.
The often-quoted “3 minutes” is a
misinterpretation: many aircraft reach ~3,000 ft in about 2–3 minutes, which has been incorrectly remembered as a time rule. The only actual time limits are
engine certification limits (5 minutes AEO, 10 minutes OEI).
B747-400: at heavy weights or with SID/obstacle constraints it is normal to hold takeoff thrust above 3,000 ft and exceed 3 minutes; this is
not an NADP violation as long as engine limits and company SOPs are respected.
Bottom line: there is no ICAO “3-minute NADP rule.”
Pertinent document