14 CFR § 125.283
Second-in-command qualifications
July 13, 2020
No certificate holder may use any person, nor may any person serve, as second in command of an airplane unless that person—
(a) Holds at least a commercial pilot certificate with appropriate category and class ratings, and an instrument rating; and
(b) For flight under IFR, meets the recent instrument experience requirements prescribed for a pilot in command in part 61 of this chapter.