14 CFR § 135.245

Except as provided in paragraph (b) of this section, no certificate holder may use any person, nor may any person serve, as second in command of an aircraft unless that person holds at least a commercial pilot certificate with appropriate category and class ratings and an instrument rating.

A second in command of a helicopter operated under VFR, other than over-the-top, must have at least a commercial pilot certificate with an appropriate aircraft category and class rating.

No certificate holder may use any person, nor may any person serve, as second in command under IFR unless that person meets the following instrument experience requirements:

Use of an airplane, powered-lift, or helicopter for maintaining instrument experience. Within the 6 calendar months preceding the month of the flight, that person performed and logged at least the following tasks and iterations in-flight in an airplane, powered-lift, or helicopter, as appropriate, in actual weather conditions, or under simulated instrument conditions using a view-limiting device:

Six instrument approaches;

Holding procedures and tasks; and

Intercepting and tracking courses through the use of navigational electronic systems.

Use of an FSTD for maintaining instrument experience. A person may accomplish the requirements in paragraph (c)(1) of this section in an approved FSTD, or a combination of aircraft and FSTD, provided:

The FSTD represents the category of aircraft for the instrument rating privileges to be maintained;

The person performs the tasks and iterations in simulated instrument conditions; and

A flight instructor qualified under § 135.338 or a check pilot qualified under § 135.337 observes the tasks and iterations and signs the person's logbook or training record to verify the time and content of the session.

A second in command who has failed to meet the instrument experience requirements of paragraph (c) of this section for more than six calendar months must reestablish instrument recency under the supervision of a flight instructor qualified under § 135.338 or a check pilot qualified under § 135.337. To reestablish instrument recency, a second in command must complete at least the following areas of operation required for the instrument rating practical test in an aircraft or FSTD that represents the category of aircraft for the instrument experience requirements to be reestablished:

Air traffic control clearances and procedures;

Flight by reference to instruments;

Navigation systems;

Instrument approach procedures;

Emergency operations; and

Postflight procedures.