Text in force at 27-51: from 27-0, effective 1 Feb 1965.
The minimum flight crew must be established so that it is sufficient for safe operation, considering--
(a) The workload on individual crewmembers;
(b) The accessibility and ease of operation of necessary controls by the appropriate crewmember; and
(c) The kinds of operation authorized under Sec. 27.1525.
29 FR 15695 · Source