Originally Posted by chimbu warrior
US FAR's provide more clarity than Australian CAR's on this. They effectively state that the duration of any absence from the flight deck should be limited to the time needed to accomplish physiological needs
Not really.
121.543
(b) A required flight crewmember may leave the assigned duty station—
(1) not relevant
(2) If the crewmember's absence is in connection with physiological needs; or
(3) not relevant
I suppose that one could say that there is an implication of a time limit but it certainly doesn't say that explicitly.