Take-off power question

Why do pilots when they take off put around 40-50% trust then put the required take off trust? Why don’t they put straight to take off thrust?

Same reason you don’t put your foot flat on the accelerator in a car. Plus you don’t want to blow a jet engine. They’re expensive


I should be more technical…Most takeoffs use “derated” thrust to save engine wear. For each takeoff, performance is calculated, the necessary power setting is determined and the thrust setting is made. Usually this is below the maximum available level and is known as a derated thrust takeoff. Derates improve engine life and reliability. In addition to lowering operating costs, they decrease the likelihood of an engine failure.


If you are refering to why they put around 40% or 50% N1 or equivalant EPR before going takeoff thrust, I think it is to do with ensuring that all engines are producing simlar levels of thrust and are spooling up in a similar rate or something like that


Yeah they move the throttles up, check all the gauges and make sure EPR has stabilized, and then they go to take off power. It’s so they can check gauges at low speed


Thanks guys.

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I always thought they did it to warm up the engines. To get them ready for takeoff. 😂

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They move it slowly to 30% to check if they are running up and stabilizing normally :)

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I believe they also do it to a certain rpm and speed then go to necessary power for takeoff for the calculated power for the amount of weight they have on board

it’s T-H-R-U-S-T not T-R-U-S-T

Assuming that you meant to type “thrust”, he pilots put a smaller amount of power on to make sure the engines are stabilized after spooling up slightly. If they’re not stablized, it might cause a compressor stall. Nothing too badly wrong with that other than it causing a very loud bang and perhaps sending some flames out the back.

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Even you can’t spell it correctly XD


As many people mentioned here before, stabilizing + preventing compressor stall.

It’s T-H-R-U-S-T.

ok sorry I just woke up when I typed it in
only NRL fans know what I mean

Pilots spool the engines up to ~50% n1, to ensure the engines are performing normally and equally. Then, on boeings, the autothrottles are engaged, which automatically advances the thrust levers to takeoff thrust, which is predetermined by the fmc based on several factors. Airbuses are effectively the same, except TOGA thrust (100%) or flex thrust (not 100%) is selected.

They have to make sure the N1 is stabilized to about 30% percent then they set take-off thrust, this is mainly used to make the sure the engines are ready for take-off, and to warm them up, if you may, it is also to make sure they are operating together, and have the same N1 overall, basically, stabilized, safe, and synchronized that’s why pilots do that, but there are still other reasons, however those are the main reasons.

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@Nicholas_L I think you’ve misunderstood. TO/GA does not mean 100%, but rather around ~90%. The aircraft itself calculates how much TO/GA should be, based on mutliple factors such as runway length, wind, all that stuff.


They put it to about 40% first so that both engines spool up to 40% and then increase to about 90%. One of the reasons is that sometimes both engines spool up at different rates so to avoid unequal thrust and preventing getting off alignment with the centreline of the runway, In addition to the reason others have mentioned above.

Thank you everybody. I was a bit confused when they had to do that but now I know the main reason of why they do it. Thanks.

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