Hello,

At one point of you approach, typically when established on final, you need to change current set ALT to missed approach ALT. When I fly an ILS approach and the G/S is captured I just can turn the ALT up to the desired value and the T7 stays on G/S captured.

Flying a RNAV approach I would need to do that change after the last WPT with a vertical restriction. Now what I experience is that when I change to the higher ALT quickly, the T7 stays on VNAV and continues, but when I just change over slowly it may initiate a VNAV capture. Is that the real behavior you need to pay attention to?

Have a look at this PDF you can download from Smartcockpit:

 

http://www.smartcockpit.com/aircraft-ressources/B777-Instrument_Approach_(Using_VNAV).html

 

Basically, the correct procedure is, while on final, to set the MCP to the missed approach altitude once you have descended through 300ft below the missed approach altitude.

 

I'm not sure about the "quick" and "slow" knob turning behaviours, but I use the above procedure and it works every time.

 

Hope it helps.

 

Mathieu