Summary

During the past 2015 Conference held in Sofia a paper about satellite approach and landing systems pointed to policies ADME 2.8 and ADME 2.10 as being outdated. The present paper deals with both policies, reviewing their meaning and objectives and proposes changes for their update.

Introduction

1.1 During the Conference of Sofia in 2015 the paper entitled Introduction to GNSS Landing Systems was presented as Working Paper 84, agenda item B.5.3. Such paper is included as an appendix.

1.2 Although it was presented as an information paper, the report pointed some policy items that were outdated. The extension of the revisions made advisable to present a separate paper included in the working program of the next Conference.

Discussion

2.1 The policies included in the Technical and Professional Manual (TPM) as ADME 2.8 and ADME 2.10 were identified in the working paper presented in Sofia and mentioned in 1.1 as relevant to the subject and worth of revision. These policies are as follows:

2.2 A third policy, the one on Mixed Mode Operations, was considered as relevant and still valid. It will be used in the revision of the other two.

2.3 The policies quoted in 2.1.1 and 2.1.2 require an explanation to be understood. They were approved at the Conference of Geneva in 2001. Fourteen years later the situation concerning new approach systems has changed and the Federation has also evolved. A summary of the circumstances in which the policy was created is required.

2.3.1 The Future Air Navigation Committee of ICAO (FANS) was stablished in 1983 and was charged to study the existing systems for their capabilities and potencial for development as well as to study new concepts and technologies.

2.3.2 FANS identified the systems being used at the time and the proposed systems for the future. For terminal areas the ILS was mentioned as a system in place but it was not considered to have a place in the future. MLS was expected to be the future standard system for approach and landing.

2.3.3 MLS is a system technically more advanced than ILS. It was designed to allow approaches with different glide slopes, curved approaches, provide operational information via datalink, etc. At present GNSS landing system is considered as the best option to replace the ILS (see appendix) but in the 1990s the substitution of the well known ILS for the MLS and its advanced features seemed imminent. 2010 was sometimes quoted as the year when the transition to MLS from ILS would probably be completed.

2.3.4 While the air navigation system seemed to be evolving quickly, the situation of IFATCA was very different from today. At present IFATCA participates in ICAO panels and activities and is present at the Air Navigation Commission. IFATCA’s voice is taken in account and its opinion is respected. But in the 1990s IFATCA was not yet in such a position, having no chance to contribute in the drafting of documents issued by ICAO. In those days IFATCA had no chance to be proactive and was forced to be reactive whenever any kind of change was foreseen.

2.3.5 Combining both elements, a change in the air navigation system that was presented as inminent and a Federation forced to be reactive, is no wonder that the policies concerning the change were very long and defensive to address some concerns that at present would be discussed at a higher level.

2.4 Discussion on ADME 2.8 and ADME 2.10

2.4.1 The policy ADME 2.8 concerning Advanced Approach Procedures dates from 2001. The same is true for the most of ADME 2.10 which deals with new approach and landing aids. Both are closely related and could be combined under a policy covering the introduction of new approach and landing systems and procedures. Paragraphs will be reviewed one by one except when two paragraphs are so related that can be examined together.

It seems clear that any procedure not demonstrating some kind of benefit would hardly be implemented so the first sentence seems to be unnecessary. About the second sentence it is covered by the Mixed Mode Operations policy quoted in 2.2 so the whole paragraph is proposed for deletion.

2.4.2

The paragraph is confusing for it proposes to classify a procedure already designated as advanced as basic or (again) advanced. The idea lying under this policy was to call advanced approaches the more complex ones (curved approaches) in opposition to ILS-like approaches. Being this terminology not used in any other document the paragraph is not needed and should be deleted.

2.4.3

This policy under ADME 2.8 and the following under ADME 2.10 are basically the same.

In the flight plan format implemented by ICAO in 2012 the capability of the aircraft is included in box 10. For example, ILS is coded by the letter L, GBAS by A, MLS by K etc. The mission of the policy under ADME 2.10 can be therefore considered as fulfilled.

Nonetheless the policy in ADME 2.8 not only refers to the flight plan but also states the need to have the controller aware of the capability of the aircraft. This second provision needs some discussion.

The approach capability of the aircraft is useful to an approach controller who is planning a sequence. But the current policy goes too far by requesting a data display system thus entering in the description of the user requirements of the system. The policy thus is to be reviewed. The following wording is proposed to substitute both paragraphs:

2.4.4

This paragraph is intended to consider the need to integrate different flows of traffic when flying complex approaches as curved ones. This feature is theoretically possible when using MLS or GBAS systems even if so far the GBAS approaches in use define an ILS-like straight path (see appendix).

A graphic example is the picture below depicting the merging of two different approaches. More approach paths could be added to the example thus increasing the complexity and making the integration of the different flows impossible to achieve without help from automation and the use of specific procedures. The policy is therefore valid but must be reworded to avoid the use of the term advanced approach.

The following wording is proposed:

2.4.5

This policy, included in ADME 2.8, has the same intention than the following one which is part of ADME 2.10:

The idea under both statements is to maintain the workload of the controller at a reasonable level by reducing the number of approaches. Nonetheless one of the reasons to introduce new approach systems is the possibility to fly more efficient paths that would eventually merge as seen in the picture. It adds complexity, true, but this complexity should not be a challenge provided that appropriate tools are available. Both paragraphs can therefore be deleted because the policy reviewed under 2.4.4. requested such kind of tools.

2.4.6

This paragraph seems unnecessary: being the controller the one who clears the aircraft to any approach, if the controller considers that the situation is too complex he/she can decide to use temporarily only part of the available approaches. The paragraph is then proposed for deletion.

2.4.7

This policy presumes that an instrumental approach can only be performed under surveillance which is not necessarily true, and enters in details about how a system must be designed. This kind of details are part of the user requirements which should not be included in the TPM but provided by the local controllers of the facility where the system is to be implemented. About the involvement of controllers in the design and development of a system, in a general sense, there is policy in the Manual:

The general involvement of controllers in the implementation of a new system is covered by this AAS 1.13 policy, being part of their role, as specifically quoted in the policy, to establish user requirements that would include, if necessary, the use of video map displays and the information to be included in them. The policy reviewed is not therefore needed and proposed for deletion.

2.4.8

This paragraph is proposed for deletion because it seems unnecessary to have a policy requesting the application of ICAO standards and recommended practices.

2.4.9

The validity indicator of an approach or departure standard procedure is defined in the Annex 11 of ICAO, appendix 3 as follows.

For example, the STAR BAN3D to Madrid airport is composed of:

• The basic indicator BAN (the name of Barahona VOR where the STAR begins
• The validity indicator 3 (the 3rd version of a STAR beginning in BAN)
• The route indicator D (indicates a route to the runway 32)

The original reason of the inclusion of this policy is unclear. The question of the responsibility of the accuracy of the data transmitted by datalink should not be limited to a very particular piece of information (the validity indicator) in a specific phase of flight (the arrival). This question should be treated in a general datalink policy instead of in a policy about approach systems. Accordingly it is proposed for deletion.

2.4.10

This paragraph can be examined jointly with the next one:

Both paragraphs refer to what they call aborted approach. This term is hardly used in ICAO documents. More common is the expression go-around but no definition of it exists either while missed approach procedure is defined in several documents. About go-around, the term may be found in the following definition in the Annex 4:

So, go-around is considered a common language expression not deserving a specific definition and it is used as a synonym of aborted approach. About missed approach the following definition may be found, for example, in the Annex 4:

It is meaningful that the expression go-around is not defined but included in a definition of visual approach procedure while there is no definition of missed approach but of missed approach procedure. According to it we can consider that go-around is a common term (hence not needing definition) referring to the process of interrupting an approach (visual or not) while the procedure to be followed during a go-around is a missed approach procedure.

About how a missed approach procedure is included in the charts, that is, how the missed approach procedure is considered, the Annex 4, chapter 11 states:

ICAO thus states that any published instrument approach must include a missed approach procedure which of course must be designed to provide separation with terrain as every instrument flight procedure must, according to ICAO Doc 8168 V1:

In conclusion both paragraphs of the policy studied here are not necessary because any approach based on a new approach system will have to comply with these ICAO provisions and include a missed approach procedure that will provide obstacle clearance. Having a published procedure, there is no need to provide radar vectors during the missed approach, specially considering that the workload for the pilot is very high during such an event and radar vectors increase it. The idea behind the policy is therefore correct but it is already considered by ICAO. Both paragraphs are accordingly proposed for deletion.

2.4.11

This policy has exactly the same intention than the following paragrah of ADME 2.10.

The only difference between both statements is that ADME 2.8 refers to procedures and ADME 2.10 to technology. Both emphasize the need to provided adequate training but the manual has a clear policy on training included in its professional part:

This policy covers both systems and procedures. The statements in ADME 2.8 and ADME 2.10 are therefore not needed and both are proposed for deletion.

2.4.12

This is the first paragraph in ADME 2.10 and clearly needs a revision if only because the term RNP (Required Navigation Performance) is now encompassed with RNAV in the PBN (Performance Based Navigation) concept. But the analysis may go further. According to ICAO Doc 9613, PBN Manual (relevant parts have been underlined).

The conclusion of the statement is clear: a precision approach and landing system which provides vertical guidance (such as MLS, GLS and the venerable ILS) is not considered part of the RNP system. There is no definition for vertical RNP at the moment.

The policy does not make the mistake to claim that a new approach and landing system must be RNP but based on the principles associated with RNP which is a vague statement. Anyhow, trying to define how a new system must be designed is out of the scope of the manual. Consequently this policy is proposed for deletion.

2.4.13

Annex 10 volume 1 defines critical and sensitive areas for ILS and MLS. In both cases a critical area is one where vehicles, including aircraft, are excluded during operations while a sensitive area is an extension of the critical area where the parking and movement of vehicles, including aircraft is controlled to prevent interferences and disturbances in the system signal.

Nothing in the annex 10 allows for a reduction of a critical or sensitive areas due to a second aid being installed. On the contrary, one reason to install systems like GBAS or MLS is the reduction in the critical areas which make possible an increase in the runway throughput but this benefit is not completely achieved until ILS operations cease completely due precisely to the need to maintain those areas protected during ILS operations (see paper included as appendix, paragraphs 2.6.1 and 2.7.6).

An example of how the co-existence of several aids to approach and landing involves the existence of all of the critical areas is found in the Annex 10 vol 1, attachment G:

It is clear that ICAO considers the need to protect the critical and sensitive areas of all the systems in place.

In view of all the above, it is not necessary to have this policy which is accordingly proposed for deletion.

2.4.14

The reason for this policy is again in what seemed to be the imminent deployment of MLS. Using this system there is a need to have an OFZ (obstacle free zone, that it is just one of the protected areas just mentioned in 2.4.13) cleared before issuing a clearance for the landing of an incoming aircraft. In low visibility conditions the only way to ensure that precedent traffic had cleared the OFZ was to use a SMR (the policy was approved in 2001, at present ADS-B or Multilateration should be considered) but the SMR was not a requirement to operate an MLS. The policy tried to ensure that it was in place so the potential of the MLS could be used.

Reading the policy 15 years later, with no need to hurry for what was expected to be the imminent arrival of MLS, the policy is puzzling and its meaning obscure without an explanation. It is therefore proposed for deletion.

2.4.15

This part of the policy was introduced in 2007. The idea behind it was that a controller should not need to issue the details of an RNP or RNAV approach. As an example of subcategories we may see the following table from ICAO Doc 8168 volume 2 (Table III-5-1-1)

The suffix here is the subcategory of the approach. According to the policy the controller does not need to know every detail and could clear an aircraft to an RNP approach to runway 23 no matter if the RNP approach is LPV (vertical guidance provided by GNSS, or LNAV/VNAV (vertical guidance based on barometric inputs). The same would apply to ILS with the controller clearing to ILS approach being the crew responsible to determine if they perform a CAT I or CAT II approach.

The same apply to the minima, the aircrew being responsible to determine them. Again, an example helps to clarify it: in the case of an ILS approach the crew should determine if the aircraft equipment is certified as well as if they are qualified to operate CAT I or CAT II being the minima dependent on that.

Seeing no reasons to change this policy, it is to be retained.

Conclusions

3.1 Policies ADME 2.8 and ADME 2.10 were approved at a time where both IFATCA and the expected evolution of the Air Navigation System were very different from today.

3.2 The need for IFATCA in those days to be reactive instead of proactive joined with what seemed an imminent change in the navigational aids used for approach and landing produced a very defensive policy on the subject.

3.3 After revision both policies have been judged as outdated and are accordingly proposed for revision.

Recommendations

It is recommended that:

4.1 IFATCA Policy

Advanced approach procedures should only be introduced where there is a demonstrated benefit from using these procedures. During any transition period these operations must not overload ATC or adversely affect its ability to handle all aircraft safely and efficiently.

in page 2 3 3 10 of the TPM is deleted.

4.2 IFATCA Policy

Advanced approach procedures should be designated under 2 categories: Basic and Advanced. The Basic procedure should be a straight in approach following the normal glidepath. An Advanced procedure is any procedure requiring a higher level of equipment.

in page 2 3 3 10 of the TPM is deleted.

4.3 IFATCA Policy

To permit advance planning, the approach capability of the aircraft should be included on the flightplan and displayed to the controller using the appropriate data display system. The flight plan data should be limited to an indication of Basic or Advanced procedures.

in page 2 3 3 10 of the TPM jointly with IFATCA Policy

To permit advanced planning the approach aid capability of the aircraft should be included in the flight plan and displayed to the controller using the appropriate data display system.

in page 2 3 3 12 of the TPM is deleted and substituted by:

Working procedures and/or systems should provide the approach capability of the flight to relevant controllers.

4.4 IFATCA Policy

ATC will require the provision of assistance tools for managing and integrating traffic operating on advanced approach procedures.

in page 2 3 3 10 of the TPM is amended to read

Assistant tools should be provided for managing and integrating traffic on different approaches to the same runway.

4.5 IFATCA Policy

The number of advanced approach procedures to any one runway should be kept to a minimum to reduce the complexity of the traffic flow in the terminal area.

in page 2 3 3 10 of the TPM is deleted.

4.6 IFATCA Policy

The variety of approach types, and the associated complexity to the controller, should be reduced.

in page 2 3 3 12 of the TPM is deleted.

4.7 IFATCA Policy

ATC should have the option to limit the number of advanced approach procedures in use at any one time.

in page 2 3 3 10 of the TPM is deleted.

4.8 IFATCA Policy

The controller should have a video map display showing the planned flight path of an aircraft on an advanced approach procedure and the track miles to touchdown.

in page 2 3 3 10 of the TPM is deleted.

4.9 IFATCA Policy

Advanced approach procedures should have a unique identification that is not dependent on the runway designator and should be named in accordance with ICAO Annex 11 Appendix 3, ‘Principles Governing the Identification of Standard Departure and Arrival routes and Associated Procedures’

in page 2 3 3 10 of the TPM is deleted.

4.10 IFATCA Policy

ATC must not be responsible for checking the validity indicator of an advanced approach procedure where this is transmitted to the aircraft by datalink.

in page 2 3 3 10 of the TPM is deleted.

4.11 IFATCA Policy

When advanced approach procedures are published, they must ensure that the aircraft is able to continue to navigate safely during an aborted approach until the aircraft has climbed to a terrain safe altitude.

in page 2 3 3 10 of the TPM is deleted.

4.12 IFATCA Policy

When an aborted approach is made from an advanced approach procedure, radar vectors must not be considered as the primary means of navigating the aircraft.

in page 2 3 3 10 of the TPM is deleted.

4.13 IFATCA Policy

Where advanced approach procedures are introduced, the additional staff training and equipment to integrate this traffic into the ATC system must be provided before these operations commence.

in page 2 3 3 10 of the TPM is deleted.

4.14 Where New Technology Approach and Landing Aids are introduced, any additional staff training and equipment to integrate this traffic into the ATC system must be provided before these operations commence.

in page 2 3 3 12 of the TPM is deleted.

4.15 IFATCA Policy

Operational procedures for New Technology Approach and Landing Aids should be based on the principles associated with RNP.

in page 2 3 3 12 of the TPM is deleted.

4.16 IFATCA Policy

Where more than one approach aid is in use the largest critical and sensitive areas must be protected.

in page 2 3 3 12 of the TPM is deleted.

4.17 IFATCA Policy

When SMR is required in operational procedures, the SMR must be serviceable and displayed to the controller during these operations. (Note: See SMR Policy).

in page 2 3 3 12 of the TPM is deleted.