Thrust Mode display

[Sweet19blue]

Hi,

I am trying to figure out how the thrust mode display is working in the 733.

The thrust mode sequence I am seeing seems odd to me but I can't find where to look in the FCOM to learn how is it working.

Here is what I am seeing on a typical flight with Derated TO and Derated Climb thrust :

- Takeoff :  R-TO

- After reduction to climb thrust : R-CLB

- During climb : Mine is remaining at R-CLB. Should the mode switch to CLB after a while during like on NG as thrust requirement increases at higher altitude.

- Leveling to cruise : Thrust mode switches to CRZ

- In descend : I am not sure what I should be expecting but I see R-CLB again. I was expecting the thrust mode to remain in CRZ.

- Landing : Thrust mode displays GA. But what are the requirements for GA to display. Being below 2000ft RA?

I would be glad if someone could explain how is it working or point me to the right FCOM chapter , my curiosity is at high level^^

Best regards,

Pierre

 

 

 

 

Edited July 13, 2016 by Sweet19blue

[dr_anthony]

45 minutes ago, Sweet19blue said:

- During climb : Mine is remaining at R-CLB. Should the mode switch to CLB after a while during like on NG as thrust requirement increases at higher altitude.

It should be and it does. If you look at CDU page N1 and at N1 bugs on ENG instr you will see after 15000 it changes from R-CLB to CLB regarding to N1 value, but on thrust modes on ENG instr and in CDU N1 page it remains R-CLB.

So many words ))). For example: R-CLB 85 CLB - 91. And it changes to 91 past FL150 if you look to N1 eng instr value. But CDU and trust mode shows R-CLB. For my opinion its a FMC model bug.

45 minutes ago, Sweet19blue said:

- In descend : I am not sure what I should be expecting but I see R-CLB again. I was expecting the thrust mode to remain in CRZ.

I think so too.

45 minutes ago, Sweet19blue said:

- Landing : Thrust mode displays GA. But what are the requirements for GA to display. Being below 2000ft RA?

Yes, it changes for GA below 2000 AGL, and provides reduced GA thrust on first press of TO/GA button, and full GA thrust on second.

Edited July 13, 2016 by dr_anthony