could someone plese explain how an INS system works hence, on the older 747's? thanks!!!INS=Inertial Navigation System

Do you mean a detailed technical description, or a description of how to use it?Anyway, to not leave you totally empty handed:Technical description (you'll see that I'm not an expert): It is a bunch of gyros and accelerometers that work together to sense the movement of the aircraft. It's quite accurate, down to a few NM. The IRS (Inertial Reference System), that you will see on for example the 747-400 and 767s, is a development of the INS. The IRS is more accurate though. On many newer aircraft they call the IRS something even more fancy, like ADIRU (Air Data Inertial Reference Unit) on the 777, and ADIRS (same as on the 777 but with "System" at the end instead of "Unit") on the Airbuses.Operationally, the INS is a little more complicated to use than the IRS coupled with an FMS. Unlike an FMS, the INS doesn't have a database of waypoints, so every waypoint must be entered with its coordinates. Also an INS usually has a relatively small memory, and can only hold 10-20 waypoints or so, so if the flight is long you can only enter the first waypoints before departure, and the rest as more memory becomes available.MartinIt's a lot like life and that's what's appealing

THANKS! so it's like a 'mini FMC..just none of the new cool buttons like on a 744 and 777

not fmx at all...just a computer giving wind pos and nothing else and of course the memory is limited to 9 points for carrousel IV to +92 pts in last one... with a lot infos on last one for some 747 like fmc including cruise and climb perfs but antoher story...you ll see it into ralf toffelmire with classic 742 panel...

Worth having a look at Ralph's Classic package - the new VMAX project looks well