Originally Posted by
cessnapete
The Cruise only pilot has no defined part in the aircraft operation, no Normal ,Abnormal or Emergency Checklist procedures involve a third man. Presumably if any in flight emergencies occur with the Capt in rest, he is immediately called, and retakes the front seat with the trained F/O, and the S/O again becomes an observer.
If the S/O is in the seat when the proverbial happens, then he completes whatever checklist/ECAM/EICAS actions are necessary with the other pilot, whether he is the Captain or an FO. The bloke who is off duty may be called back, or he may not, but if I arrive back on the cockpit I expect the procedures to be complete.
And, having had major event when operating 3 man, the SO made himself extremely useful whilst carrying out the jobs that you dismiss.