Thread: All engine vs single engine departures
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Old 05-12-2015 | 08:04 AM
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Adlerdriver
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From: 767 Captain
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Originally Posted by cougar
In regard to all engine acceleration height, turbojet aircraft generally have to comply with NADP 1 or NADP 2 departure procedures. Some airports specify which is required, either for near or far noise sensitive areas. These departure procedures are found in AC 91-53A, JAR-OPS 1.235 or PANS OPS Vol 1 Doc 8168.

NADP 1 (Near) requires a thrust reduction at or above 800' and climb at V2 +20 until no more than 3000' accelerate and retract flaps.

NADP 2 (far) accelerates at or above 800', and reduces thrust at or after flap retraction.

It is surprising that your SOPs call for flap retraction at 400'. The regs quoted above apply to part 135, but not familiar with your aircraft certification requirements.
Those NADP procedures normally apply to aircraft operating over 75,000 lbs. TOGW. His aircraft isn’t in that category. Noise abatement procedures have no correlation with aircraft certification requirements and there are some aircraft out there that simply cannot comply with the profiles you listed.

Originally Posted by cougar
2nd segment climb starts at gear retraction to a minimum of 400'. Most operators use an EO accel height greater than 400' (800 or 1000, etc) due to net and gross flight path and obstacle clearance.

Many operators have their standard EO accel height and the all engine accel height the same (Our fleet uses 1000'). However, for obstacles in 2nd or third segment climb, the EO accel altitude will be higher.
That works fine if the aircraft has the EO performance to allow a higher acceleration altitude or the convenience of matching normal and EO acceleration altitudes in their procedures. That level of performance is usually attainable with most large transport category aircraft these days.

One part of the equation that can be a factor is the engine time limit at takeoff power. Certification limits on an engine out takeoff require that the power cannot be reduced to MCT until the aircraft is clean. I believe the minimum certification limit for jet engines at T/O power is 5 minutes. A performance limited aircraft may not have the luxury of a climb above 400 feet before accelerating and retracting flaps. To do so might require several additional minutes at T/O power and exceed that engine operating limit.
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