All Parts Part 135 Subpart C—Aircraft and Equipment § 135.147
§ 135.147

Dual controls required

No person may operate an aircraft in operations requiring two pilots unless it is equipped with functioning dual controls. However, if the aircraft type certification operating limitations do not require two pilots, a throwover control wheel may be used in place of two control wheels.

Sourced from eCFR · Title 14 CFR · for educational reference only — fly the latest regs.