14 CFR § 61.191
Additional flight instructor ratings
July 13, 2020
(a) A person who applies for an additional flight instructor rating on a flight instructor certificate must meet the eligibility requirements listed in §61.183 of this part that apply to the flight instructor rating sought.
(b) A person who applies for an additional rating on a flight instructor certificate is not required to pass the knowledge test on the areas listed in §61.185(a)(1) of this part.
[Doc. No. 25910, 62 FR 16298, Apr. 4, 1997; Amdt. 61-103, 62 FR 40907, July 30, 1997]