I would like to correct something that has been said... All 747s (from the prototype -100 series) came with triple INS capability when delivered new from Boeing. However, you always had the option to fly it using only navigation radios. The switch you talk about allows you to feed INS data to the flight director and autopilot, or you could use the navigation radios (VOR, ILS) instead. Now, some 747s were later modified to include GPS or IRS units to replace the INS because it was bulky, heavy and expensive to maintain. Some were even fitted with full-blown FMSs. I don't know of any operator who removed the INS units and did not replace them with something equivalent - this is a long-range airplane. I know about the Japanese domestic 747SRs, and those had INSs too. So if you want to fly a 747 Classic without messing with the INS, you can do that and simply slave the needles to the nav radios and just use the INS to indicate present position, drift, wind, or whatever without loading a flight plan. On another note, I have some good resources/manuals for P&W 747 Classics so if there is something I can help with, let me know. I also have a good buddy who flew it recently so he should be able to answer some technical questions (P&W, INS and FMS models). Finally, I am greatly looking forward to this. The 747 is my favorite plane of all time, and I even have some time in the 747-300 full motion sim - she was a beauty to fly, powerful, and very stable. I managed to fly without crashing or damaging it, even though I was only a student pilot at the time. - Stekeller KORD