The logic behind FLT DIR?

But since you activate both of these modes on the ground in the 777, I thought there might be something extra I didn't know about...

You can arm LNAV and VNAV in both the 777 and in the later FMC revisions for the NG (including the revision modelled in the NGX). Activation occurs at 50 FT RA for LNAV and 400 FT RA for VNAV.

Usage of the Flight Director in the NG and 777 is similar:

• switch goes on during the preflight flows
• switch goes off during the shutdown flows
• when intentionally deviating from flight director indicates (e.g. visual approach or visual circling), in the NG, you recycle the switch to clear the bars; in the 777, the switch simply goes off because recycling will give you HDG/TRK HOLD and VNAV ALT. In both aircraft, pressing a TO/GA switch will bring up the flight director bars in TO/GA TO/GA regardless of the flight director switch position.