CFM 56 thrust bump on the FMC

[gumbyjan]

The questionis:

We have a 7B24 with a 24k thrust bump on the FMC N1 page. When we select this rating do we get more than 24k, and how much. Will the bugs move up to a higher N1 on the Upper DU than the a full 24k selection?

[CaptainSandL]

The take-off thrust bump will give you more than 24K, how much more I don’t know, I suspect it depends upon the ambient conditions. Yes the bugs will move higher up than normal, to figure given at N1 LIMIT 1/1 Field 1R.

TO-B is intended for emergency use only, eg windshear, terrain avoidance etc; so the extra thrust capability is not normally used.

Full details should be in your FCOM Vol 2 under Engines - EEC and also Flight management - FMC – Thrust Management

S&L

[gumbyjan]

Thanks for the help. Is TO-B the DU display that indicates that you selected 24K bump on the FMC? Cheers

[CaptainSandL]

Yes.
Actually my typo in prev post, the thrust mode display is "TO B" (not TO-B).