14 C.F.R. § 139.327
(a) In a manner authorized by the Administrator, each certificate holder must inspect the airport to assure compliance with this subpart according to the following schedule:
(b) Each certificate holder must provide the following:
(3) Procedures to ensure qualified personnel perform the inspections. Such procedures must ensure personnel are trained, as specified under § 139.303, and receive initial and recurrent instruction every 12 consecutive calendar months in at least the following areas:
(c) Each certificate holder must—