---
kind: "section"
citation: "14 C.F.R. § 171.263"
title: "14"
number: "171.263"
heading: "Localizer automatic monitor system."
url: "https://uscodex.org/cfr/14/171.263"
---

# §171.263. Localizer automatic monitor system.

- (a) The ISMLS localizer equipment must provide an automatic monitor system that transmits a warning to designated local and remote control points when any of the following occurs:
  - (1) A shift of the mean course line of the localizer from the runway centerline equivalent to more than 0.015 DDM at the ISMLS reference datum.
  - (2) For localizers in which the basic functions are provided by the use of a single-frequency system, a reduction of power output to less than 50 percent of normal or a loss of ground station identification transmissions.
  - (3) Changes of displacement sensitivity to a value differing by more than 17 percent from nominal value for the localizer.
  - (4) **Failure of any part of the monitor itself.** Such failure must automatically produce the same results as the malfunctioning of the element being monitored.
- (b) Within 10 seconds of the occurrence of any of the conditions prescribed in [paragraph (a)](#a) of this section, including periods of zero radiation, localizer signal radiation must cease or the navigation and identification components must be removed.

## Notes

### Source

Source: Docket 14120, 40 FR 36110, Aug. 19, 1975, unless otherwise noted.

### Authority

Authority: 49 U.S.C. 106(g), 40103-40107, 40109, 40113, 44502, 44701-44702, 44708-44709, 44711, 44719-44721, 45303, 46308.

### Source

Source: Docket 5034, 29 FR 11337, Aug. 6, 1964, unless otherwise noted.