Review Policy on Separation Lateral and Longitudinal

  • Home 2005 Review Policy on Separation La....

Review Policy on Separation Lateral and Longitudinal

44TH ANNUAL CONFERENCE, Melbourne, Australia, 17-22 April 2005

WP No. 89

Review Policy on Separation Lateral and Longitudinal

Presented by TOC

Introduction

1.1. As part of the 2004/2005 Work Programme, TOC was tasked to review policy on lateral and longitudinal separation.

1.2. Present IFATCA policy dates from 1986.

Discussion

2.1. The lead-in text of IFATCA policy, reference IFATCA Manual 3273, para 7.2, states:

“The rules governing the application of lateral and longitudinal separation which are contained in PANS-RAC Part 3 are deficient in several respects and many ATC administrations have found it necessary to amplify or extend their provisions.

Therefore IFATCA Policy is that:

“IFATCA has grave reservations concerning the application and interpretation of horizontal non-radar separation as detailed in ICAO PANSRAC Doc 4444. Of particular concern are those minima laid down for lateral separation and for aircraft on crossing tracks. IFATCA is of the opinion that ICAO should conduct an urgent review of these non-radar separation minima and should take steps to ensure that they are unambiguous.”

 

Since 1986, ICAO has published several amendments to the former PANS-RAC, now called PANS-ATM, relative to this subject:

  • Amendment 1 to the 13th Edition, applicable 6 November 1997
    Source: Air Navigation Commission.
  • Amendment 2 to the 13th Edition, applicable 5 November 1998
    Source: Review of the General Concept of Separation Panel, Ninth Meeting (1996).
  • Amendment 1 to the 14th Edition, applicable 28 November 2002
    Source: Review of the General Concept of Separation Panel, Tenth Meeting (2000).

The reference above, PANS-RAC Part 3, was the chapter on Area Control Service and the separation of aircraft in the provision of area control service. The following paragraphs will discuss the policies in detail. Whether or not this lead-in text is still applicable depends on the outcome of these discussions.

2.2.

“In conducting this review ICAO should have regard to the following:

1. Except in accordance with PANS-RAC 3-12 and 4-1, separation standards shall not be reduced below ICAO minima.”

 

In the absence of a 1986 edition of the PANS-RAC, TOC is of the opinion that the references PANS-RAC 3-12 and 4-1 correspond to “Clearances to fly maintaining own separation while in Visual Meteorological Conditions” and “Reduction in separation minima” respectively.

“Clearances to fly maintaining own separation while in Visual Meteorological Conditions” was significantly amended in Amendment 3 to the 13th Edition, applicable 4 November 1999, source: Air Navigation Commission, reference PANS-ATM 5-9. “Reduction in separation minima” stipulates in what circumstances separation minima may be reduced. The 14th Edition of the PANS-RAC, re-titled PANS-ATM, provides for a comprehensive update of this paragraph and reflects provisions and procedures relating to safety management of Air Traffic Services.

PANS-ATM 2-6 “Safety Assessments” and in PANS-ATM 5-11 “Reduction in separation minima” now states:

“Provided an appropriate safety assessment has shown that an acceptable level of safety will be maintained, and after prior consultation with users, the separation minima detailed in 5.4.1 and 5.4.2 may be reduced in the following circumstances…”

As the PANS-ATM is concurrent with IFATCA policy, it is proposed to delete this policy.

2.3.

“2. Published separation standards are to state that they contain an element of separation to allow for track keeping errors or time keeping errors. This element should be published within the source documents on ATC separation standards”.

The application of Lateral Separation, PANS-ATM 5-4-1 refers, states that this application should account for navigational inaccuracies plus a specified buffer. This buffer shall be determined by the appropriate authority and included in the lateral separation minima as an integral part thereof.

As the PANS-ATM is concurrent with IFATCA policy, it is proposed to delete this policy.

2.4.

“3. Publications promulgating separation standards are required to include guidance material on practical methods of application and the associated phraseology”.

This policy remains valid and it is therefore proposed for retention.

2.5.

“4. ICAO should define procedures in order that ATS is always made aware of a known divergence from track”.

In accordance with Annex 2, pilots intending to deviate from the centre line of an ATS route are required to obtain authorization.

However, ICAO has published guidelines to use lateral offsets as a safety measure to reduce the risk of collision in the event of loss of vertical separation. The authorization required by Annex 2 can be achieved by coordinated publication of approved offset procedures, by NOTAM and in Aeronautical Information Publication (AIP), by all States concerned. In airspace where the use of lateral offsets has been authorized, pilots are not required to inform ATC that an offset is being applied. IFATCA does not oppose these guidelines and supports a standardized and coordinated application.

As Annex 2 is concurrent with IFATCA policy, it is proposed to delete this policy.

2.6.

“5. ICAO should define the terms ‘Crossing track’, ‘Diverging track’ and ‘Converging track’ noting that the definition will require a stated angular value between tracks.”

PANS-ATM has renamed and re-defined the terms, including a stated angular difference:

  • Lateral separation: Intersecting Tracks, (reference PANS-ATM 5.4.1.2.1.5)
  • Longitudinal separation: Same Track, Reciprocal Track and Crossing Track, (reference PANS-ATM 5.4.2.1.5)

PANS-ATM has published definition on the respective terms. This makes the policy redundant and it is therefore proposed for deletion.

2.7.

“6. ATC are required to establish that all aircraft about to be separated by methods involving track difference are established on those appropriate tracks before applying the separation.”

PANS-ATM 5-4 requires that “both aircraft are established on…”

PANS-ATM is concurrent with IFATCA policy. This makes the policy redundant and it is therefore proposed for deletion.

2.8.

“7. When DME readings are used to apply longitudinal separation between aircraft on the same track, the same ‘on track’ DME station should be used by both aircraft.”

PANS-ATM 5-4 requires that “each aircraft utilizes “on-track” DME stations”.

PANS-ATM is concurrent with IFATCA policy. This makes the policy redundant and it is therefore proposed for deletion.

Conclusions

3.1. ICAO has conducted an extensive review of the non-radar separation minima.

3.2. With the exception of one, all policies concur with ICAO publication.

3.3. The policy statement regarding additional guidance material remains valid.

Recommendations

It is recommended that;

4.1. IFATCA policy on page 3 2 7 3 para 7.2:

“IFATCA has grave reservations concerning the application and interpretation of horizontal non-radar separation as detailed in ICAO PANS-RAC Doc 4444. Of particular concern are those minima laid down for lateral separation and for aircraft on crossing tracks. IFATCA is of the opinion that ICAO should conduct an urgent review of these non-radar separation minima and should take steps to ensure that they are unambiguous. In conducting this review ICAO should have regard to the following:

1. Except in accordance with PANS-RAC 3-12 and 4-1, separation standards shall not be reduced below ICAO minima.

2. Published separation standards are to state that they contain an element of separation to allow for track keeping errors or time keeping errors. This element should be published within the source documents on ATC separation standards.

3. Publications promulgating separation standards are required to include guidance material on practical methods of application and the associated phraseology.

4. ICAO should define procedures in order that ATC is always made aware of a known divergence from track.

5. ICAO should define the terms ‘Crossing track’, ‘Diverging track’ and ‘Converging track’ noting that the definition will require a stated angular value between tracks.

6. ATC are required to establish that all aircraft about to be separated by methods involving track difference are established on those appropriate tracks before applying the separation.

7. When DME readings are used to apply longitudinal separation between aircraft on the same track, the same ‘on track’ DME station should be used by both aircraft.”

be deleted.

4.2. IFATCA Policy is:

Publications promulgating separation standards are required to include guidance material on practical methods of application and the associated phraseology.

And be included in the IFATCA Manual on page 3273.

References

ICAO Annex 2.

ICAO PANS-ATM, Doc 4444.

Last Update: September 29, 2020  

March 26, 2020   272   Jean-Francois Lepage    2005    

Comments are closed.


  • Search Knowledgebase