SA CIVIL AVIATION REGULATIONS
PART 91: GENERAL AVIATION AND OPERATING FLIGHT RULES
91.02.3 Crew member responsibilities

(1) No person shall act as a crew member of an aircraft—

(a) whilst using any psychoactive substance which may affect his or her faculties in any manner that may jeopardise safety;

(b) within 24 hours following scuba diving by such flight crew member;

(c) within 72 hours following blood donation by such flight crew member;

(d) if the crew member knows or suspects that he or she is suffering from or, having due regard to the circumstances of the flight to be undertaken, is likely to suffer from fatigue to such an extent that it may endanger the safety of the aircraft or its occupants; or

(e) if the crew member is in any doubt of being able to accomplish his or her assigned duties on board the aircraft.