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JamesDinsdale

Legs Cruise altitude disagree

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Good day everyone,

 

Been a very long time since I last flew the 777 (over 8 months ago) due to being out of the country & away from my computer. But having just come back to it and started all over again, I am still confused over an issue that bugged me when I flew this plane more regularly:

 

My cruise altitude selected in the VNAV ECON Cruise page of the FMC is F350 under CRZ ALT, on the right hand side of the page its preloaded the STEP TO FL370. But when I go to my LEGS page the first waypoint has the altitude set at .MACH/FL370. 

 

Why is this? I have 35000 set in my autopilot panel but as I reach TOC the flight plan automatically changes to FL370 as a type of 'step climb' (which is enabled). But why does it do this when I want to cruise at FL350 initially? Is it because of the STEP TO FL370 AT NOW? If so how can I delay the step climb until I want it to?

 

Hope that makes a bit of sense to someone,

 

Thanks

 

James Dinsdale

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Is it because of the STEP TO FL370 AT NOW?

 

What are the OPT, MAX and RECMD flight levels on the VNAV ECON CRZ page? Probably the weight of the aircraft is already low enough to climb to a higher cruise altitude, and there is no "need" to wait with the step climb.

 

 

 

If so how can I delay the step climb until I want it to?

 

You can put a letter "S" to the altitude on the LEGS page. So instead of ".mach/FL370" you write ".mach/FL370S" for the waypoint at which you want to perform the step climb to FL370.

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You have enabled auto step climb, a convenience feature the real 777 doesn't have. So when you reach cruise the FMC steps to 370 because the conditions for a step climb are satisfied. Try it with auto step climb disabled. The legs page will probably still show 370 as the optimum level but altitude will remain at the cruise altitude selected by you.

 

While relearning the 777 it's probably best to turn off the auto cruise feature so you remain in control. I'd recommend leaving it off to stay realistic, but that's just my opinion.

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