14 C.F.R. § 171.273 – Maintenance and operations requirements.

(a) The owner of the facility must establish an adequate maintenance system and provide qualified maintenance personnel to maintain the facility at the level attained at the time it was commissioned. Each person who maintains a facility must meet at least the Federal Communications Commission's licensing requirements and show that he has the special knowledge and skills needed to maintain the facility, including proficiency in maintenance procedures and the use of specialized test equipment.
(b) In the event of out-of-tolerance conditions or malfunctions, as evidenced by receiving two successive pilot reports, the owner must close the facility be ceasing radiation, and issue a “Notice to Airman” (NOTAM) that the facility is out of service.
(c) The owner must prepare, and obtain approval of, an operations and maintenance manual that sets forth mandatory procedures for operations, periodic maintenance, and emergency maintenance, including instructions on each of the following:
1. (1) Physical security of the facility.
2. (2) Maintenance and operations by authorized persons.
3. (3) FCC licensing requirements for operations and maintenance personnel.
4. (4) Posting of licenses and signs.
5. (5) Relation between the facility and FAA air traffic control facilities, with a description of the boundaries of controlled airspace over or near the facility, instructions for relaying air traffic control instructions and information, if applicable, and instructions for the operation of an air traffic advisory service if the facility is located outside of controlled airspace.
6. (6) Notice to the Administrator of any suspension of service.
7. (7) Detailed and specific maintenance procedures and servicing guides stating the frequency of servicing.
8. (8) Air-ground communications, if provided, expressly written or incorporating appropriate sections of FAA manuals by reference.
9. (9) Keeping of station logs and other technical reports, and the submission of reports required by § 171.275.
10. (10) Monitoring of the ISMLS facility.
11. (11) Inspections by United States personnel.
12. (12) Names, addresses, and telephone numbers of persons to be notified in an emergency.
13. (13) Shutdowns for periodic maintenance and issue of “Notices to Airmen” for routine or emergency shutdowns.
14. (14) Commissioning of the ISMLS facility.
15. (15) An acceptable procedure for amending or revising the manual.
16. (16) An explanation of the kinds of activities (such as construction or grading) in the vicinity of the ISMLS facility that may require shutdown or recertification of the ISMLS facility by FAA flight check.
17. (17) Procedures for conducting a ground check of the localizer course alignment, width, and clearance, glide path elevation angle and course width, and marker beacon power, and modulation.
18. (18) The following information concerning the ISMLS facility:
  1. (i) Facility component locations with respect to airport layout, instrument runways, and similar areas.
  2. (ii) The type, make, and model of the basic radio equipment that provides the service.
  3. (iii) The station power emission and frequencies of the ISMLS localizer, glide path, beacon markers, and associated compass locators, if any.
  4. (iv) The hours of operation.
  5. (v) Station identification call letters and method of station identification and the time spacing of the identification.
  6. (vi) A description of the critical parts that may not be changed, adjusted, or repaired without an FAA flight check to confirm published operations.
(d) The owner or his maintenance representative must make a ground check of the ISMLS facility periodically in accordance with procedures approved by the FAA at the time of commissioning, and must report the results of the checks as provided in § 171.275.
(e) Modifications to an ISMLS facility may be made only after approval by the FAA of the proposed modification submitted by the owner.
(f) The owner or the owner's maintenance representative must participate in inspections made by the FAA.
(g) Whenever it is required by the FAA, the owner must incorporate improvements in ISMLS maintenance.
(h) The owner or his maintenance representative must provide a sufficient stock of spare parts, including solid state components, or modules to make possible the prompt replacement of components or modules that fail or deteriorate in service.
(i) FAA approved test instruments must be used for maintenance of the ISMLS facility.
(j) The mean corrective maintenance time of the ISMLS equipment may not exceed 0.5 hours, with a maximum corrective maintenance time of not greater than 1.5 hours. This measure applies to failures of the monitor, transmitter and associated antenna assemblies, limited to unscheduled outage and out-of-tolerance conditions.
(k) The mean time between failures of the ISMLS equipment may not be less than 1,500 hours. This measure applies to unscheduled outages, out-of-tolerance conditions, and failures of the monitor, transmitter, and associated antenna assemblies.
(l) Inspection consists of an examination of the ISMLS equipment to ensure that unsafe operating conditions do not exist.
(m) Monitoring of the ISMLS radiated signal must ensure a high degree of integrity and minimize the requirements for ground and flight inspection. The monitor must be checked periodically during the in-service test evaluation period for calibration and stability. These tests and ground checks of glide slope, localizer, and marker beacon radiation characteristics must be conducted in accordance with the maintenance requirements of this section.