Text in force at CS25-28: from CS25-18, effective 24 Jun 2016.
(See AMC 25.1523) The minimum flight crew must be established (see AMC 25.1523) so that it is sufficient for safe operation, considering –
(a) The workload on individual crew members;
(b) The accessibility and ease of operation of necessary controls by the appropriate crew member; and
(c) The kind of operation authorised under CS 25.1525. The criteria used in making the determinations required by this paragraph are set forth in Appendix D.
ED Decision 2016/010/R · Source