Sorry !!  >:(

If this happen to experts like you Markoz,  think about the struggle a newbie like me has to undergo.

I do all the things as per the tutorials and half way through the flight the VNAV gets disengaged !  :(  

All further adjustments are to be made manually and it is nothing better or special - just like the normal aircrafts where you do all the settings in  AP (GPS and NAV).  This is after doing all the fixes as suggested by you Markoz in a different tutorial.

My biggest problem is I am unable to understand one thing - after doing every thing in FMC if I have to again go on manipulating the A/P (speed and altitude)  then what is great or special about this aircraft ? But every one claims so and I would definitely like to know the tricks so that I can also call this aircraft a great one !!

Awaiting your tutorial

tupulur