---
kind: "section"
citation: "14 C.F.R. § 171.319"
title: "14"
number: "171.319"
heading: "Approach elevation monitor system requirements."
url: "https://uscodex.org/cfr/14/171.319"
---

# §171.319. Approach elevation monitor system requirements.

- (a) The monitor system must act to ensure that any of the following conditions do not persist for longer than the periods specified when:
  - (1) There is a change in the ground component contribution to the mean glidepath error component such that the path following error on any glidepath exceeds the limits specified in [§ 171.317(d)](/cfr/14/171.317.md?p=d) for a period of more than one second.
  - (2) There is a reduction in the radiated power to a level not less than that specified in [§ 171.317(a)(4)](/cfr/14/171.317.md?p=a-4) for a period of more than one second.
  - (3) There is an error in the preamble DPSK transmission which occurs more than once in any one second period.
  - (4) There is an error in the time division multiplex synchronization of a particular elevation function such that the requirement specified in [§ 171.311(e)](/cfr/14/171.311.md?p=e) is not satisfied and this condition persists for more than one second.
  - (5) **A failure of the monitor is detected.**
- (b) The period during which erroneous guidance information is radiated must not exceed the periods specified in [§ 171.319(a)](#a). If the fault is not cleared within the time allowed, radiation shall cease. After shutdown, no attempt must be made to restore service until a period of 20 seconds has elapsed.

## Notes

### Source

Source: Docket 20669, 51 FR 33177, Sept. 18, 1986, 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.