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I used to think that for commercial aircraft from Airbus, Boeing, Embraer, etc., the take off power was always maximum and selected by the TOGA selection on the thrust levers. But I have been told that some companies would lower the takeoff power to save money (at the expense of a longer take-off length).

So the question is: for regional, continental, and long-haul aircraft, is the takeoff power always maximum or can it be adjusted depending on the configuration? And can lowering takeoff power allow savings?

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Takeoff power is almost never maximum engine power.

  1. Maximum power affects engine life as it brings significant wear to the engine. IIRC, if max power is used on takeoff, the crew must log an entry in the logbook to notify maintenance.
  2. Turbo-fans produce a lot of power. If you require max power to takeoff, you better double-check your numbers, or you're operating with a pretty narrow margin.

The reality is the reverse: airlines love to do low power takeoffs, and they avoid a high power takeoff as much as practical. Occasionally, a condition such as high ambient temperature (resulting in high pressure altitude), heavy load, obstacle on departure path may demand a max power takeoff. Possible wind shear may also prompt the crew to select a higher takeoff power.

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  • $\begingroup$ Typically, how much margin is available above takeoff power for max engine power? $\endgroup$ – curious_cat Feb 9 '17 at 6:05
  • $\begingroup$ Also if take off power isn't max engine power, when is max engine power used? Any circumstances you can think of? Is go around thrust at max engine power? $\endgroup$ – curious_cat Feb 9 '17 at 6:06
  • $\begingroup$ @curious_cat: max power is used in unusual situations, such as in turbulence, wind shear, go around, engine failure etc. Usually, around 90~95% N1 is sufficient on takeoff. In very good conditions, it may even be slightly below 90% (e.g. 87 or 88%). $\endgroup$ – kevin Feb 9 '17 at 9:59
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Is the takeoff power always maximum?

No, unless it is required.

Disadvantages for using full power on takeoff is higher fuel consumption, noise, and engine wear.

Instead, takeoff performance is calculated and the appropriate thrust setting is used.

You need lower setting if:

  1. runway is long
  2. no obstacle to clear during climb
  3. runway is dry
  4. temperature is low
  5. headwind is fast
  6. airport is low (altitude)

All the above would increase your allowed payload and/or fuel load, and/or allow reduced thrust.

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