Do I always have to use the APU ? Kind regardsNigel Thomas-Smith

Nope, you can make the elderly go up inside the engines and make them use the little air in their lungs to get the fans spinning, and after 2 hours when they reach 20%N1 you will yell fuel on and they will jump out so they don't get ingested.Apu is mandatory for the PMDG 737, because it does not have external air functionality.As for the 747, Apu for engine start if optional if you have ground/air power selected in the menu(it is by default) you can use that. I'm sure you know how to do the regular start procedure( you know, pulling the the button and fuel cutoff to on etc...) so i will not waste time explaining it.

THANKS. All is revealed.Kind regardsNigel Thomas-Smith