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I have watched many aircraft takeoffs now where the flight deck announce 'Thrust Set', just after the engines are set to full.

Forgive the dumb question, but why does one announce that the thrust is set, perhaps more importantly, why is it necessary in the takeoff procedure?

I did attempt some research before posting, but the closest article I got did not make much sense to me I am afraid.

For the GE CF6 engines, N1 should be stable at 70% before the TO/GA switch is pushed to set the armed thrust limit. If TO/GA is not pushed by 50 knots, thrust must be set manually and when VNAV goes active at 400', the A/T will automatically go active in THR REF, so you don't need to select anything if the A/T is armed.

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  • $\begingroup$ The flying pilot calls "set thrust" and the non-flying pilot sets the thrust to the precomputed amount. $\endgroup$
    – Steve Kuo
    Commented Feb 26, 2018 at 21:57
  • $\begingroup$ @SteveKuo, the RAC's answer disagrees with you (pilot-looking-in is PM, PF must be looking out). $\endgroup$
    – Jan Hudec
    Commented Oct 23, 2018 at 20:59

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There was at least one incident where a Boeing 737 attempted to takeoff with the throttle levers not set to takeoff power.

The procedure is designed to ensure

  • the thrust lever is where it is supposed to be
  • the engine indications show the correct amount of power is produced

In some airlines, the procedure calls for both pilots to put their hands on the levers and advance them together. Either way, the purpose is to have both the pilot flying and pilot monitoring to ensure takeoff power is properly applied.

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    $\begingroup$ The main problem wasn't the throttle position in Air Florida 90. The engine EPR indication was incorrect due to probe icing. The thrust levers are set to a target EPR and were properly set based on the indicated values. The only thing that would have mattered is the pilot's "feel" for the proper position in this scenario. $\endgroup$
    – user71659
    Commented Feb 27, 2018 at 4:12
  • $\begingroup$ @user71659 while there are no markings along the throttle positions, an experienced pilot will naturally move them to the usual position after executing hundreds of takeoffs. In the Air Florida 90 case, the throttle were advanced to the proper position, but were eased back after the (incorrect) EPR exceeded the expected value. $\endgroup$
    – kevin
    Commented Feb 27, 2018 at 5:28
  • $\begingroup$ Qualifying Air Florida 90 (78 fatalities) as an "incident" is a bit an understatement... see aviation.stackexchange.com/questions/14074 . Might want to edit that... $\endgroup$
    – kebs
    Commented Mar 3, 2018 at 14:04
  • $\begingroup$ @user71659, these days in most aircraft either A/T that moves the thrust levers, or they are moved into a MCT/FLX detent and FMS assigns it meaning according to the programmed values, so feel does not help any more. $\endgroup$
    – Jan Hudec
    Commented Oct 23, 2018 at 20:57
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The "Thrust Set" call is an announcement by the Pilot-Looking-In to the Pilot-Looking-Out that the thrust is what they wanted, and what they need for the Takeoff.

In addition, the call has to come before the "80 knots" (or equivalent) call so that the proper amount of thrust has been set before there is too much ram-rise affecting the thrust setting.

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