Introduction & Background
This topic contains only those PANS-AIM requirements relevant for a Microwave Landing System (MLS). For general PANS-AIM requirements valid for all kind of Radio navigation aids see topic Navaid [NAV] and subordinated pages.
ICAO Annex 10, Volume I:
MLS is a precision approach and landing guidance system which provides position information and various ground to air data. The position information is provided in a wide coverage sector and is determined by an azimuth angle measurement, an elevation angle measurement and a range (distance) measurement.
An MLS consists of two main components
- Azimuth equipment: An SHF transmitter and associated equipment, radiating signals in a volume of airspace served by the MLS, thereby furnishing azimuth indications to aircraft approaching the runway or back azimuth indications to aircraft departing from the runway or performing a missed approach procedure.
- Elevation equipment: SHF transmitter, and associated equipment radiating signals within a volume of airspace served by the MLS, thereby furnishing elevation information as an angular value to aircraft approaching the runway.
The range measurement is provided by a related DME.
For an MLS PANS-AIM requires some specific properties as part of the minimum AIP data set. These are
... identification, name, ... hours of operation, ..., channel..., position, ..., magnetic bearing, true bearing, ...
In addition, PANS-AIM AD2.19/AD 3.18 require
...type of supported operation for ILS/MLS, ... and for VOR/ILS/MLS also station declination ...used for technical line-up of the aid;
...If the operating authority of the facility is other than the designated governmental agency, the name of the operating authority shall be indicated in the remarks column. Facility coverage shall be indicated in the remarks column.
AIP context
The figure below shows an outdated publication of an MLS in an AIP.
The diagram below shows the AIXM classes, including the relevant data types, needed to encode that information. The main classes are Azimuth and Elevation, which is a specialisation of the NavaidEquipment.
Designator & Name
The Azimuth will have designator coded.
In general, the Elevation will not have a value for the designator attribute. If yes, it shall be identical to the designator of the localizer.
In general, neither the Azimuth nor the Elevation will have a name.
Hours of Operation
See topic Hours of Operation for Navaid.
Azimuth Channel
The Azimuth.channel attribute is used to code indicating the channel on which the Microwave Landing System is operating.
The corresponding data type class CodeMLSChannelType provides a list of values in a range from '500' to '699'.
Position
For more details see topic Navaid Position & Elevation.
Glide Path Angle
For the minimum/conditional AIP data set, the normal glide path angle of an MLS is actually not required by PANS-AIM (it is only listed in the PANS-AIM Appendix 1).
The angle of the glide path is coded using the Elevation.angleNominal and the Elevation.angleAccuracy attributes.
Station Declination
PANS AIM Appendix 1 requires a station declination for an MLS.
AIXM 5.1(.1) issue_031_Azimuth Station declination
In contrary to the VOR and ILS class, for the Azimuth no declination and Zero Bearing Direction attribute is provided. In AIXM 5, this information can only be coded with a Note.
Workaround AIXM 5.1(.1): Code a corresponding Note.
Status AIXM 5.2: To be reported to the CCB
Type of Supported Operation
In AIXM 5, the type of supported operation (e.g. CAT IIIA) is coded using the Navaid.signalPerformance attribute. Hence, the signal performance level indicating the precision of an MLS is not encoded for a particular component, but the whole MLS system.
Note
In addition, the Azimuth.type attribute may be used to code if the MSL is a 'normal' ('FWD') or 'back' ('BWD') azimuth equipment.
For more information about the coding of an MLS system, see topic Navaid Component & Navaid Colocation.
Operating Authority
See topic Operating Authority for Navaid.
Facility Coverage
See topic Facility coverage.
Served Runway Direction
In AIXM 5, the runway direction the MLS is provided for has to be coded using the Navaid.runwayDirection property. The corresponding relationship isInstalledAt indicates that the navaid (i.e. the MLS system) is installed at a particular landing area. Hence, not a component of the MLS, but the whole MLS system will be related to a particular runway direction. For more information about the coding of an MLS system, see topic Navaid Component & Navaid Colocation.
Coding Rules for MLS
| Identifier | Data Encoding Rule | Justification | Data Verification Rule (UID) | Remarks |
|---|---|---|---|---|
| MLS-101 | The Azimuth.designator attribute is mandatory. | Minimum AIP data set | TBD | |
| MLS-102 | The Azimuth.channel attribute is mandatory. | Minimum AIP data set | TBD | |
| MLS-103 | The Azimuth.location property is mandatory. | Minimum AIP data set | TBD | |
| MLS-104 | The Elevation.location property is mandatory. | Minimum AIP data set | TBD | |
| MLS-105 | The Elevation.angleNominal attribute is mandatory. | PANS-AIM | TBD | |
| MLS-106 | The Elevation.angleAccuracy attribute should be provided. | PANS-AIM | TBD | |
| MLS-107 | The Elevation.angleMinimum attribute should be provided. | PANS-AIM | TBD | |
| MLS-108 | Either the Azimuth.magneticBearing or the Azimuth.trueBearing attribute shall be provided. | Minimum AIP data set | TBD | |
| MLS-109 | If the Azimuth.magneticBearing is provided than the Azimuth.magneticBearingAccuray should be provided. | PANS-AIM | TBD | |
| MLS-110 | If the Azimuth.trueBearing is provided than also the Azimuth.trueBearingAccuray should be provided. | PANS-AIM | TBD | |
| MLS-111 | If Navaid.type equal-to 'MLS or 'MLS_DME' the Navaid.signalPerformance shall be provided. | PANS-AIM | TBD | |
| MLS-112 | The Navaid.signalPerformance and the related RunwayDirection.precisionAppraochGuidance shall be consistent. | Data consistency | TBD | For example, if signalPerformance is CAT IIIA also the precisionAppraochGuidance shall be CAT IIIA. |
| MLS-113 | If Navaid.type equal-to 'MLS' or 'MLS_DME' it must have exactly one NavaidEquipment which is an Azimuth. | Data consistency | TBD | |
| MLS-114 | If Navaid.type equal-to 'MLS' or 'MLS_DME' it must have exactly one NavaidEquipment which is an Azimuth. | Data consistency | TBD | |
| MLS-115 | The value of the DME.channel of the related DME must be paired with the Azimuth.Channel as described by Table A, ICAO Annex 10, Vol.1. | EAD | ||
| MLS-116 | The Azimuth.location must be plausibly close (less than 1 KM) to that of the end of the related (through Navaid.runwayDirection) RunwayDirection. | EAD / Data consistency | TBD | |
| MLS-117 | The difference between Azimuth.magneticBearing and the related RunwayDirection.magneticBearing (through Navaid.runwayDirection) cannot exceed 10 degrees. | EAD / ICAO Doc 8168, PANS OPS | TBD | |
| MLS-118 | The difference between Azimuth.trueBearing and Azimuth.magneticBearing has to be consistent with the value of the AirportHeliport.magneticVariation of the related AirportHeliport (through Navaid.servedAirport), taking in consideration the current date and the annual rate of change (AirportHeliport.magneticVariationChange). | EAD | TBD | |
| MLS-119 | The Elevation.location must be plausibly close (less than 1 KM) to that of the threshold of the related (through Navaid.runwayDirection) RunwayDirection. | EAD | TBD | |
| MLS-120 | Elevation.angleNominal must be greater than Elevation.angleMinimum. | EAD/ ICAO Annex 10, Vol. 1 | TBD |
Coding Examples
As there is hardly any MLS installation in the world remaining, it is not considered necessary to provide an example of an MLS in the scope of the DONLON AIXM AIP data set.