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No Back Azimuth.

Part 2 Requirements
3  Safety Objective
The equipment shall provide a complete, identified, accurate and uncorrupted source of guidance information to aircraft, with levels of integrity and continuity of service which are consistent with the category of service provided.
4  System Requirements
4.1  ICAO SARPs Compliance
In addition to the requirements below, Microwave Landing Systems shall comply with the Standards and Recommended Practices (SARPs) in ICAO Annex 10, Volume 1, Chapter 2 General Provisions for Radio Navigation Aids, and Chapter 3, Section 3.11 Specification for MLS (2212).
NOTE:  Where the UK has differences filed to SARPs, these will be published in Supplements to the Annexes and in the UK AIP.
5  Integrity and Continuity of Service
5.1  The MLS shall meet the ICAO Annex 10 Volume 1 Standards and Recommended Practices (SARPS) for Integrity and Continuity of Service found in Chapter 3.11 (2213).
5.2  Maintenance shall be prescribed in accordance with the Integrity Analysis (2336).
6  Serviceability Indicators
6.1  Flight Information Service Officers and/or Air Traffic Controllers directly responsible for MLS operations (e.g. Approach Controllers) shall be provided with:
a) visual indications showing the serviceability status of all elements of the MLS including power supplies (2214); and
b) an audible alarm indicating when the visual indications have changed state (2215).
6.2  Failure of Status Communications
6.2.1  Permitting a status communications failure to shut down the MLS without a warning could unnecessarily remove the MLS signal when the aircraft is in a critical phase of the approach.
6.2.2  Failure of status communication between the MLS equipment and the remote status indicators shall cause an immediate alarm at the remote indicators (2216).
6.2.3  For Category II and III systems, failure of the status communication shall not cause an immediate MLS close-down (2217).
6.2.4  For Category I systems, it is acceptable to consider status communication failure as part of the Continuity of Service assessment (2218).
6.2.5  Following failure of the status communications, only aircraft on final MLS approach shall be permitted to complete the approach. The MLS shall then be withdrawn from service in accordance with a documented procedure (2219).
6.2.6  If the MLS is configured to close down the system after a delay following status communications failure, the delay must be long enough for the actions in paragraph
6.2.5 to be completed (2220).
6.2.7  In the event of a status communication failure, a suitably trained technician may be stationed at the MLS building(s) with a suitable means of communication to ATC. The equipment should then operate in local control, supervised by the system monitors. The monitors shall not be overridden or inhibited. ATC must be advised without delay of any change in status of the MLS (2221).
6.2.8  A reciprocal MLS shall not be put into service until the system with faulty status communications is positively disabled and cannot accidentally radiate (2222).
7  Category and Status Unit
7.1  In addition to the normal remote control and other indications, Category III facilities shall be fitted with a unit that accepts signals from the MLS equipment, its monitors and the runway direction switch, to provide ATC automatically with indications of the operational category of the MLS (2223).
NOTE:  The precise method of calculation used by the Category and Status Unit will depend on the MLS equipment from which it derives its inputs. Guidance material is provided in MLS 01 Annex 1.
7.2  The unit shall have an integrity as determined by a hazard analysis (2224).
7.3  Any change of calculated category shall cause an audible alarm to ATC (2225).
　
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