Anybody here ever tried an in-flight alignment?
I've tried an on-ground IRS alignment during a maintenance tow on a 747-400 (similar generation). Even on the straight sections with few bumps in the tarmac and minimal speed changes, the IRS MOTION message eventually appears and the countdown restarts (although not always immediately after the selector knobs are set to NAV).
Old and new IRSs? I can't see them retrofitting 767s/744s (with GPS) with new systems that can align in flight simply because of a few cases of operator error. Have any in-flight incidents proved fatal? I seem to recall a PPRuNe message thread on an incident in Nepal.