ILS and Localizer Only

Page Table of Content

Introduction & BackgroundDesignator & NameAerodrome ServedHours of OperationMagnetic VariationFrequencyPositionLocalizer Course (bearing)Localizer WidthLocalizer antenna rwy end distance & ILS glideslope antenna TRSH distance, ILS DME antenna TRSH distance & ILS marker TRSH distanceStation DeclinationGlide Path AngleRDHType of Supported OperationOperating AuthorityFacility CoverageServed Runway DirectionNavaid Component

ILS/Localizer without DMEILS/Localizer with DME

Coding ExamplesReferences

Introduction & Background

This topic contains only those PANS-AIM requirements, which are relevant for an Instrument Landing System (ILS) and a Localizer only system. For general PANS-AIM requirements valid for all kind of Radio navigation aids, see topic and subordinated pages.Navaid [NAV]

According to ICAO Annex 10, Volume I , the ILS shall comprise the following basic components:[1]

a) VHF localizer equipment (for horizontal guidance),

b) UHF glide path equipment (for vertical guidance),

c) VHF marker beacons, or distance measuring equipment (DME) (for range information).

A standalone instrument approach installation without an associated glidepath is a Localizer system (also called Localizer only or Localizer without GP, etc.)

Also locators (NDB) may be used as a supplement to the ILS/localizer system. They should be located at the sites of the outer and middle marker beacons. Where only one locator is used as a supplement to the ILS, preference should be given to location at the site of the outer marker beacon.

For an ILS & Localizer system, PANS-AIM requires some specific properties as part of the minimum AIP data set. These are

... identification, name, aerodrome served, hours of operation, magnetic variation, frequency..., position, ..., magnetic bearing, true bearing, ...

In addition, PANS-AIM AD 2.19/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.

The diagram below shows the AIXM classes, including the relevant data types and code lists, needed to encode that information. The main classes are and , which are specialisations of the .Localizer Glidepath NavaidEquipment

Designator & Name

The will have a  coded.Localizer designator

In general, the will not have a value for the attribute. If yes, it shall be identical to the designator of the localizer.Glidepath designator

The shall carry the same as the Navaid designator Localizer.

In general, neither the nor the nor the will have a . However, local naming conventions may be applied (e.g. Navaid Localizer Glidepath name ILS ). In case naming conventions are applied they should be consistent for all data provided by the same data 27R or LLZ RWY 27R or GP RW-27R

provider.

Aerodrome Served

See topic .Basic Data for Navaid

Hours of Operation

See topic .Hours of Operation for Navaid

Magnetic Variation

For ILS, PANS-AIM Appendix 1 requires the magnetic variation to be provided. For details about the encoding including rules see the topic Magnetic .Variation

Frequency

The attribute is used to code the value of the frequency of the localizer.Localizer.frequency

The attribute is used to code the value of the frequency of the glidepath.Glidepath.frequency

This can be any decimal value greater than 0. However, there is a coding rule that defines a range of acceptable values.

The corresponding data type contains an attribute. For both and , only the value ' ' shall be ValFrequencyType uom Glidepath Localizer equal-to MHZused.

According to ICAO Annex 10, Volume 1 [1]

The localizer shall operate in the band 108 MHz to 111.975 MHz.

The glide path equipment shall operate in the band 328.6 MHz to 335.4 MHz.

Localizer and glidepath frequency will be paired according to ICAO Annex 10, Volume I.

Position

For more details see topic .Navaid Position & Elevation

Localizer Course (bearing)

The magnetic bearing of a Localizer (or Localizer course) is the measured angle between the localizer beam and Magnetic North at the localizer antenna and is coded using the attribute. This is the inbound course value, when going towards the Localizer antenna, Localizer.magneticBearingas normally provided in AIS publications. In addition, the is used to provide the corresponding accuracy value. Localizer.magneticBearingAccuracyIn general, this information is published on an approach chart.

At some locations of the world, rather a true than a magnetic bearing may be published for the Localizer course. Anyhow, PANS-AIM also requires to code the true bearing, i.e. the measured angle between the localizer beam and True North at the localizer antenna. This also is an inbound course value, when going towards the Localizer antenna. The and attributes are used to code that Localizer.trueBearing Localizer.trueBearingAccuracyinformation.

The accuracy required by PANS-AIM is 1/100 degree.

In case either the true or the magnetic bearing is provided, for the other attributes a should be provided.nilReason

Localizer Width

This information is not required by PANS-AIM. Also, the ARINC 424   "Airport and Heliport Localizer and Glideslope Records (PI)" contain a [2]

"Localizer Width (LOC WIDTH)" data field.

In AIXM the attribute may be used to code the localizer's course width, in degrees.Localizer.courseWidth

In addition the corresponding attribute may be coded.Localizer.courseWidthAccuracy

In some AIPs this information is published.

AIP context

The example show the publication of a true bearing in an AIP.

Localizer antenna rwy end distance & ILS glideslope antenna TRSH distance, ILS DME antenna TRSH distance & ILS marker TRSH distance

The "Localizer antenna rwy end distance" defines the location of the facility antenna relative to one end of the runway in terms of a distance.

The" ILS glideslope antenna TRSH" distance defines the location of the antenna with respect to the runway threshold.

 It indicates the distance from a line drawn at right angles to the runway at the antenna position to the threshold of the runway.

Also the distances form the ILD DME and/or ILS marker to the threshold of the runway might be provided.

This information is not required as minimum/conditional data for the AIP data set, but is defined in PANS-AIM Appendix 1 (Aeronautical Data Catalogue). In ARINC 424  for the record type "Airport and Heliport Localizer and Glideslope (PI)"  contains corresponding data fields for the [2]

Localizer & Glidepath Position.

In AIXM 5.1(1) this information can only be coded by providing a corresponding for the and/or feature,annotation Localizer Glidepath

This information may also be found in AIPs,

AIP context

The example below shows the publication of the LLZ course width in an AIP.

Station Declination

The station declination for an ILS is the angular difference between true north and magnetic north at the localizer antenna site at the time the magnetic bearing of the localizer course was established.

It is coded using the attribute.Localizer.declination

Glide Path Angle

For the minimum/conditional AIP data set, the angle of the glide path is actually not required by PANS-AIM (it is only listed in the PANS-AIM Appendix 1). However, in most AIP this information will be published. Also the corresponding ARINC 424 record type for "Airport and Heliport Localizer/Glideslope" contains a "Glideslope Angle (GS Angle)" data field.

The angle of the glide path is coded using the and the attributes.Glidepath.slope Glidepath.angleAccuracy

ICAO Annex 10 defines the ILS glide path angle as follows:[1]

The angle between a straight line which represents the mean of the ILS glide path and the horizontal.

AIP context

The example below shows the publication of the distances from various components of the ILS facility to the runway threshold.

According to ICAO Annex 10 the glide path angle has to be between 1° and 5°.

Normally it is adjusted to an approach angle of 3°.

RDH

For the minimum/conditional AIP data set, the Reference Datum Height (RDH) is actually not required by PANS-AIM (it is only listed in the PANS-AIM Appendix 1). However, in most AIP this information will be published.

According to ICAO PANS-OPS the RDH is[3]

The height of the extended glide path or a nominal vertical path at the runway threshold.

 The corresponding ARINC 424 record type for "Airport and Heliport Localizer/Glideslope" contains a data field for "Threshold Crossing Height [2]

(TCH)" which is defined as

...the TCH value will be the Glideslope Height at the landing threshold for runways with ILS...

The value of the ILS Reference Datum Height (ILS RDH) is coded using the and the attributes.Glidepath.rdh Glidepath.rdhAccuracy

Accoding to ICAO Annex 10, the height of the ILS reference datum for ILS will be 15 m (50 ft). A tolerance of plus 3 m (10 ft) is permitted.

The corresponding data type for the RDH value contains an attribute. For a , only the value ' ' (meter) or ' ' (feet) shall be uom Glidepath equal-to M FTused.

Type of Supported Operation

According to ICAO Annex 10, Volume I , the lowest authorized ILS minimums, with all required ground and airborne systems components operative, [1]

are:

(a) Category I. Decision Height (DH) 200 feet and Runway Visual Range (RVR) 2,400 feet (with touchdown zone and centre line lighting, RVR 1,800 feet);

(b) Category II. DH 100 feet and RVR 1,200 feet;

(c) Category IIIa. No DH or DH below 100 feet and RVR not less than 700 feet;

(d) Category IIIb. No DH or DH below 50 feet and RVR less than 700 feet but not less than 150 feet; and

(e) Category IIIc. No DH and no RVR limitation.

In AIXM 5, the type of supported operation is coded using the attribute. Hence, the signal performance level indicating Navaid.signalPerformancethe precision of an ILS is not encoded for the localizer and glidepath separately, but for the whole ILS or Localizer system.

Note

RDH and TCH

The FAA Aeronautical Information Manual (AIM) defines Threshold Crossing Height (TCH):[4]

The theoretical height above the runway threshold at which the aircraft’s glide slope antenna would be if the aircraft maintained the trajectory established by the mean ILS glide slope or MLS glidepath.

The Transport Canada Aeronautical Information Manual (AIM) defines Threshold Crossing Height (TCH):[5]

The height of the glide path (GP) above the runway threshold.

Threshold Crossing Height is referred to as Achieved Reference Datum Height (ARDH). It is often assumed that RDH and TCH are the same. Indeed, in an ideal world, with perfectly flat terrain, they would, to all intents and purposes be the same.

However, in AIXM 5 there is no dedicated field to record the TCH. Thus, unless explicitly stated that TCH and RDH are different, the RDH attribute may also be used to encode the TCH value. If TCH and RDH are different, the TCH may be recorded as for the .Note Glidepath

At some aerodromes, a localizer "back course" is provided. This allows for a non-precision approach in the opposite direction to a front course approach without glide path information.

In case the localizer radiates a usable backcourse signal, the attribute will be encoded with ' '.Localizer.backCourseUsable YES

In case it shall explicitly be stated that the localizer is not useable backcourse, the attribute shall be encoded with ' '.Localizer.backCourseUsable NO

Operating Authority

See topic .Operating Authority for Navaid

Facility Coverage

See topic .Facility coverage

Served Runway Direction

In AIXM 5, the runway direction for which the localizer/glidepath has been set up is coded using the property. The Navaid.runwayDirectioncorresponding relationship indicates that the navaid (i.e. the ILS or Localizer system) is installed at a particular landing area. Hence, not isInstalledAtthe localizer or glidepath, but the whole ILS system will be related to a particular runway direction.

Note

In AIXM 5, the degree to which navigation aids provide accurate approach guidance for a runway direction will be encoded using the precisi attribute of the class. In case data is provided for both attributes, it has to be ensured that it is onApproachGuidance RunwayDirection

not contradictory, i.e. the ILS category defined for the runway direction cannot be higher than the one of the ILS system serving the runway direction.

AIXM 5.1(.1) issue_030_precisionApproachGuidance CATIID

RunwayDirection.precisionApproachGuidance has a value ' ' .ILS_PRECISION_CAT_IIID

Workaround: Do not use CAT_IIID

Status: see CCB AIXM-159

Navaid Component

ILS/Localizer without DME

According to ICAO Annex 10, Volume I , for an ILS without a collocated DME, there shall be two marker beacons in each installation. A third marker [1]

beacon may be added.

The marker beacon system shall be adjusted to provide coverage over the following distances, measured on the ILS glide path and localizer course line:

a) inner marker (where installed): 150 m plus or minus 50 m (500 ft plus or minus 160 ft);

b) middle marker: 300 m plus or minus 100 m (1 000 ft plus or minus 325 ft);

c) outer marker: 600 m plus or minus 200 m (2 000 ft plus or minus 650 ft).

The marker beacons shall operate at 75 MHz with a frequency.

This kind of ILS/Localizer system will be coded as a ' ' or ' ' with corresponding instances, as a Navaid.type equal-to ILS LOC NavaidEquipmentminimum with a .Localizer

In case of ' ', also a has to be coded (in case the glidepath of an ILS is inoperable, this will be coded using the Navaid.type equal-to ILS Glidepath Nav class, see also topic ).aidOperationalStatus Hours of Operation for Navaid

For the range indication one up to three instances of will be coded, each of them having a different MarkerBeacon NavaidComponent. value, i.e. ' ', ' ', ' ', see also topic .markerPosition OUTER MIDDLE INNER Marker Beacon

In case the ILS/Localizer can also be flown backcourse, an additional with 'MarkerBeacon NavaidComponent.markerPosition equal-to BACKCOUR' will be coded.SE

In case an forms part of the ILS installation, in general it will be a Locator (i.e.  ' ') see also topic .NDB NDB.type equal-to L NDB

The may be left empty, as in general an ILS will not be used as for a NavaidComponent.providesNavigableLocation SignificantPoint SegmentPoi for a route or terminal procedure.nt

For the , the will not be coded as it is not co-located with any other component of the ILS.Localizer NavaidComponent.collocationGroup

Also for the , the will not be coded as it is not co-located with any other component of the ILS.Glidepath NavaidComponent.collocationGroup

In case a is not co-located with any other component of the ILS the will not be coded.MarkerBeacon NavaidComponent.collocationGroup

A instances co-located with an   gets a unique sequential number value for the attribute, MarkerBeacon NDB, NavaidComponent.collocationGroupe.g. the outer marker will get the value ' ', the middle marker the value ' ', etc.1 2

Each that is collocated with a , will get the same number value for the attribute as the NDB MarkerBeacon NavaidComponent.collocationGroup Mar carries.kerBeacon

The and the shall have a . In general, are identified by morse code only, e.g. ' '  for the Outer marker, ' ' Localizer NDB designator MarkerBeacon - - . -for the Middle marker (Currently it is possible to code the dash and dots in AIXM 5.1(.1) for a designator. See topic  for coding details).Marker Beacon

In general, the will not have a value for the Glidepath designator.

AIP context

The figure below shows an example of how the components of an ILS may be published in an AIP in AD 2.19.

The figure below illustrates the coding of collocations of navaid equipments part of an ILS.

This ILS for Runway 30 is composed of a glidepath (GP) collocated with the DME, carrying the designator 'LJB'. In addition it comprises a locator (L) that is co-located with the outer marker (OM), both having the designator 'MG'.

The localizer (LOC) and the middle marker (MM) also forming part of the ILS are not co-located with any navaid equipment.

The following examples show an ILS for which backcourse operations are allowed and another one for which it is explicitly specified that the localizer cannot be used for backcourse.

ILS/Localizer with DME

A DME may be used as an alternative to ILS marker beacons for the range indication. The DME channel may be paired with the localizer frequency.

This kind of ILS/Localizer system will be coded as a ' ' or ' ' with corresponding instances, Navaid.type equal-to ILS_DME LOC_DME NavaidEquipmentas a minimum with a and a .Localizer DME

The of the will be identical with the one of the .designator DME Localizer

In case the is collocated with the , both will have same number value for the .DME Glidepath NavaidComponent.collocationGroup

Coding Examples

Coding examples can  be found in the :AIP Data Set - Specimen (DONLON)

No. Description XPath Expression

NAV-EX-06

LLZ-EX-01

GPT-EX-01

NDB-EX-02

MKR-EX-02

MKR-EX-03

ILS with MM and LOM //aixm:NavaidTimeSlice [@gml:id ='NAV_OXS'] |

//aixm:LocalizerTimeSlice [@gml:id ='LLZ_OXS'] |

//aixm:GlidepathTimeSlice [@gml:id ='GPT_OXS'] |

//aixm:NDBTimeSlice [@gml:id ='NDB_KL'] |

//aixm:MarkerBeaconTimeSlice [@gml:id ='MKR_OM27R'] |

//aixm:MarkerBeaconTimeSlice [@gml:id ='MKR_MM27R']

References

1. 1 2 3 4 ICAO Annex 102. 1 2 3 ARINC 424

Specification3. 1 ICAO Doc 8168,

Procedures for Air Navigation Services, Aircraft Operations, Volume I, Flight Procedures, Fifth edition - 2006

4. 1 FAA, AERONAUTICAL INFORMATION MANUAL, OCTOBER 12, 2017

5. 1 Transport Canada, Aeronautical Information Manual (TC AIM), October 11, 2018