Shortly after takeoff an aircraft will pull the thrust back a bit. This is called Derating but how do I know how much to pull the thrust back? Any Real World Pilots our Airline pilots out there that wouldn’t mind giving advice? Thanks in advance!
I think the person for this question is @Yuan_Tugo.
De-rating is limiting the take-off thrust applied during the take-off roll. It’s used where full engine performance is not required to safely adhere to the departure profile thus saving wear on the engines.
What you are referring to is the acceleration altitude where the aircraft is nosed down and accelerated. The thrust is reduced from take-off thrust to climb power predominantly for noise abatement procedures. The engineers don’t like us pesky pilots using full power as it dramatically shortens the life and service intervals of the engines!!!
In general, climb to 1000’ above airfield level (AAL) and bring the power back from T/O thrust by approx 10%. Lower the nose and allow the aircraft to accelerate, if you’re heavy then you might be close to a level segment. When the aircraft is ‘clean’ then keep the thrust setting and raise the nose to climb at your fixed airspeed/Mach No.
Thanks for the helpful response! To avoid going over 250kias under 10,000ft should I pull the power back even more or should I just pitch up a bit?
Off-topic but what is the meaning of ‘clean’?
And would there be instances where de-rating is not needed?
«Clean» refers to flaps retracted and gear up. You have a clean configuration of the aircraft to minimize drag.
As Andre_S has replied!
There are some instances where de-rating is not allowed. If the departure performance required full power, if you as the operating Captain demand a full power take off, when an MEL item requires full power, in Windshear conditions and departing from a contaminated runway.
Those are the ones I can think of off the top of my head. I’m sure there are probably others.
V2+15-25 is what I usually do. And I almost never take off with more than 90% N1.
Use your pitch to control the speed and accept the V/S it gives you.
AKA if you’re going too fast, then pitch higher, and if you’re going to slow, then pitch lower.
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