Many Thanks for the data and explanations.
Regarding the quick align thing, it sounds a bit odd to me that attitude and orientation (as I understand it's the case - I may be wrong) are allowed not to be reset at any possible occasion given their critical importance.
As for the transfer switch on the 73 CL, more precisely, my question is to know whether when selected to one side (out of "normal" mode), the opposite side IRS is still taken into account by the FMC for navigation if it does not show any fault...
Many Thanks