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ID:

AIXM-498

target version:

AIXM 5.2

version:

1.0

last updated:

24 JUN 2021

status:

PROPOSED

Table of Contents
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Description

The list of values for approachType attribute of the InstrumentApproachProcedure class is updated. Some values (such as GALILEO, DME_DME, etc.) are removed, while other values (such as SRA, GLS, etc.) are added.

Rationale for change

See: https://aixmccb.atlassian.net/browse/AIXM-249, https://aixmccb.atlassian.net/browse/AIXM-250

In the earlier AIXM versions (4.5), the IAP feature has an attribute called CODE_TYPE_RTE defined as “a code indicating the type of Instrument Approach Procedure. E.g. VOR/DME Approach, Instrument Landing System (ILS), NDB Approach, GPS Approach, etc.”  The list of values was directly derived from the ARINC 424 Route Type for Airport Approach (PF) records and it includes values such as “N (NDB)”,  “L (Localizer only)”, “E (RNAV, GPS Required)”, etc.

In AIXM 5, this attribute was replaced by the approachType attribute, defined as “A name describing the type of radio navigational aid/system”. The list of values of the new attribute kept most of the values of the previous model version attribute that referred to a navaid system.

The purpose and the intended use of this attribute needs to be clarified. Although the definition does not say it explicitly, the intention is to identify the navigation equipment/system that is used for the final approach segment and that is normally part of the procedure identifier. This is based on the PANS-OPS rules for conventional procedures identification (Volume II, Part I, Section 4, 9.5.1.2.1): “The chart identification for procedures requiring ground-based navaids shall only contain the name describing the type of radio navigation aid providing the final approach lateral guidance. Precision approach systems such as ILS or MLS shall be identified by the system name (ILS, MLS, etc.). If two radio navigation aids are used for final approach lateral guidance, the chart identification shall only include the last radio navigation aid used.

For example: if an NDB is used as the final approach fix and a VOR is used as the last navaid on the final approach to runway 06, the procedure shall be identified as VOR Rwy 06. If a VOR is used for the initial approach followed by a final approach to Rwy 24 using an NDB, the procedure shall be identified as NDB Rwy 24.

For Performance-based Navigation (PBN) approaches, PANS-OPS, Volume II, Part III, Section 5, indicates that the same requirements for procedure publication as for conventional procedures apply, unless there are specific requirements in Section 5. Item 1.4.2 essentially requires that, after November 2022, the term “RNP” is used to identify such procedures (e.g. “RNP RWY 23”) except for the GBAS precision approaches that are identified using the term “GLS”. This can be followed by a “parenthetical suffix” in particular conditions, such as “(LPV only)” when the procedure has only an LPV Minima line, “(AR)” for an RNP AR APCH navigation specification. There are also two transitional values specified, applicable until 30 Nov 2022: “RNAV (GNSS)” and “RNAV (RNP)”, but the term RNAV is no longer used in the PBN procedures identification after that date. Therefore, the type RNAV needs to be preserved for the moment, but to be used only for non-PBN approaches.

On the other hand, there are many examples of procedure chart identifiers that do not strictly follow the ICAO rules. For example, “NDB/DME”, “VOR/DME”, etc. - although DME is not providing lateral guidance for the final leg. Therefore, the definition of the approachType attribute correction needs to take into consideration both the ICAO rules and the fact that there are several common deviations from this rule.

The ARINC 424 list of values for Airport Approach (PF) and helicopter Approach (HF) records is also considered in this change proposal.

Thus, the CodeApproachBaseType list of values is updated to contain only the values that correspond to one of the following criteria:

  • values that identify the navaid equipment used for lateral guidance on the final approach, such as ILS, VOR, GLS, etc.
  • values that identify a combined navaid equipment, although only one of the components is used for lateral guidance on the final approach but which appear frequently in the procedure name, such as VOR/DME, NDB/DME.

The proposed changes are discussed in detail in the following table:

Coded value

Definition

Reason to change

[new] SRA

Surveillance Radar

PANS-OPS provides procedure design guidelines for surveillance radar.

ASR

Airport surveillance radar (ASR)

No change

ARA

Airborne radar approach (ARA)

No change

ARSR

Air Route Surveillance Radar

No change

PAR

Precision Approach Radar

No change

ILS

Instrument landing system (ILS)

No change

ILS_DME

Instrument landing system with Direction measuring equipment

DME is a not a type of lateral guidance system for final approach. From the PANS-OPS point of view, it is an ILS approach. It is also not in the ARINC 424 list of values.

ILS_PRM

Instrument landing system using a Precision runway monitor

“Precision runway monitor” is not a type of lateral guidance system. A separate change proposal will deal with PRM and parallel approaches.

LDA

Localizer Type Directional Aid

No change

LDA_DME

Localizer Type Directional Aid with Distance Measuring Equipment.

No change. It’s a combined equipment used as such in the procedure names.

LOC

Localizer only

No change.

LOC_BC

Localizer Back course

No change.

LOC_DME

Localizer with Distance Measuring Equipment

The final lateral guidance is provided by the Localizer. It is not a combined equipment and it does not appear in the ARINC 424 list of values.

LOC_DME_BC

Localizer with Distance Measuring Equipment back course

The final lateral guidance is provided by the Localizer back course. It is not a combined equipment and it does not appear in the ARINC 424 list of values.

MLS

Microwave Landing System

No change.

(new) MLS_AZM

Microwave Landing System - Azimuth Only

Non-precision approach type in PANS-OPS

MLS_DME

Microwave Landing System with Distance Measuring Equipment.

The lateral guidance is provided by the MLS system. It is not a combined equipment and it does not appear in the ARINC 424 list of values.

NDB

Non-Directional Beacon.

No change.

NDB_DME

Non-Directional Beacon with Distance Measuring Equipment.

The final lateral guidance is provided by the NDB. However, it is  a combined equipment and it also appears in the ARINC 424 list of values.

(new) DF

High frequency direction-finding (VDF) station

There exist real world procedures with this type.

SDF

Simplified Directional Facility.

There exist real world procedures with this type.

TLS

Transponder Landing System.

There exist real world procedures with this type.

VOR

VHF Omnidirectional Radio

No change.

VOR_DME

VHF Omnidirectional Radio with Distance Measuring Equipment.

The final lateral guidance is provided by the VOR. However, it is  a combined equipment and it also appears in the ARINC 424 list of values.

TACAN

UHF Tactical Air Navigation beacon

No change

VORTAC

VHF Omnidirectional Radio with UHF Tactical Air Navigation beacon

The final lateral guidance is provided by the VOR. However, it is  a combined equipment and it also appears in the ARINC 424 list of values.

DME

Distance Measuring Equipment

DME does provide lateral guidance. It is not a combined equipment and it does not appear in the ARINC 424 list of values.

DME_DME

Distance Measuring Equipment with Distance Measuring Equipment.

This is probably an RNP approach for which DME/DME navigation is authorised. But it remains an RNP approach.

RNP

Required Navigation Performance.

No change.

GPS

Global Positioning System

This will be kept for the moment because these are not PBN procedures. They are legacy procedures based on GPS only.

GLONASS

GLONASS

This is an RNP approach type. The GNSS system used will be coded through a direct association, see the new GNSS model proposal.

GALILEO

GALILEO

This is an RNP approach type. The GNSS system used will be coded through a direct association, see the new GNSS model proposal.

RNAV

Area Navigation (not PBN)

Transitional term, used only until DEC 2022.

IGS

Instrument Guidance System

No change.

(new) GLS

GBAS Landing System

Approach type listed in PANS-OPS and in the real-world.

OTHER

Other

 

Note: the InstrumentApproachProcedure.name attribute can be used to provide the final approach identifier, such as “ILS RWY 08”, “GLS RWY 26”, “RNP RWY 23 (LNAV/VNAV only)”, etc. This can also accommodate approach procedures that apply a non-standard or transitional naming, such as “LOC/DME Procedure West”, “IGS-Z RWY 34”, “RNAV (GNSS) RWY 23”, etc.

Impact assessment

When receiving data from AIXM 5.1(.1) implementations, AIXM 5.2 systems will have to be able to map forward the values that were removed into OTHER:... values, as described in the mapping rules further in this document.

When receiving data from AIXM 5.2 implementations, current AIXM 5.1(.1) systems will have to be able to map back the new values into OTHER:... values, as described in the mapping rules further in this document.

Change Proposal details

In the UML model:

  • In the InstrumentApproachProcedure class update the definition of the approachType to read “The component of the procedure identifier that indicates either the ground-based navigation system used for the final approach segment (usually limited to the system used for lateral guidance), or an indication that it is an RNP or (legacy) RNAV approach.
  • In the CodeApproachBaseType list of values make the following changes:
    • add SRA = Surveillance Radar
    • add MLS_AZM = Microwave Landing System - Azimuth Only
    • add DF = High frequency direction-finding (VDF) station
    • add GLS = GBAS Landing System
    • modify LOC = Localizer only
    • modify RNAV = Area Navigation (not PBN)
    • remove ILS_DME
    • remove ILS_PRM
    • remove LOC_DME
    • remove LOC_DME_BC
    • remove MLS_DME
    • remove DME
    • remove DME_DME
    • remove GLONASS
    • remove GALILEO

The following UML class diagram shows the modified list of values:

Mapping AIXM 5.1.1 to AIXM 5.2 (forward)

[MAPC-01] The following algorithm shall be applied:

  • For each InstrumentApproachProcedure that has the following approachType values:
    • Replace “ILS_DME” with “ILS”
    • Replace “ILS_PRM” with “ILS”
    • Replace “LOC_DME” with “LOC”
    • Replace “LOC_DME_BC” with “LOC_BC”
    • Replace “MLS_DME” with “MLS”
    • Replace “DME” with “OTHER:DME”
    • Replace “DME_DME” with “OTHER:DME_DME”
    • Replace “GLONASS” with “OTHER:GLONASS”
    • Replace “GALILEO” with “OTHER:GALILEO”
    • Replace ‘OTHER:SRA” with “SRA”
    • Replace ‘OTHER:MLS_AZM” with “MLS_AZM”
    • Replace ‘OTHER:DF” with “DF”
    • Replace ‘OTHER:GLS” with “GLS”

Mapping AIXM 5.2 to AIXM 5.1.1 (backward)

[MAPC-01] The following algorithm shall be applied:

  • For each InstrumentApproachProcedure that has the following approachType values:
    • Replace ‘SRA” with “OTHER:SRA”
    • Replace ‘MLS_AZM” with “OTHER:MLS_AZM”
    • Replace ‘DF” with “OTHER:DF”
    • Replace ‘GLS” with “OTHER:GLS”

Mapping example

(Note: for mapping test data see: https://github.com/aixm/mapping_52_511/tree/master/AIXM-xxx

AIXM 5.2AIXM 5.1(.1)
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