Text in force at 29-59: from 29-0, effective 1 Feb 1965.
(a) If there are mixture controls, each engine must have a separate control, and the controls must be arranged to allow--
(1) Separate control of each engine; and
(2) Simultaneous control of all engines.
(b) Each intermediate position of the mixture controls that corresponds to a normal operating setting must be identifiable by feel and sight.
29 FR 16150 · Source