Survey of Safety Nets Practices in Military ATM - … · Survey of Safety Nets Practices in Military ATM ... The Survey of Safety Nets Practices in Military ATM extends the SPIN

EUROPEAN ORGANISATION FOR THE SAFETY OF AIR NAVIGATION

EUROCONTROL

EUROPEAN AIR TRAFFIC MANAGEMENT PROGRAMME

Survey of Safety Nets Practices in Military ATM

Edition Number : 1.0 Edition Date : 23/12/05 Status : Released Issue Intended for : Restricted Audience


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DOCUMENT CHARACTERISTICS

TITLE


EATMP Infocentre Reference: 05/12/23-01

Document Identifier Edition Number: 1.0

Edition Date: 23/12/05

Abstract This report provides the most relevant findings of the Survey of Safety Nets Practices in Military ATM

Keywords Safety Nets STCA TCAS SNET MSAW Implementation policies APM APW

Contact Person(s) Tel Unit Ben Bakker 93146 DAS/ATS

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EATMP Infocentre EUROCONTROL Headquarters 96 Rue de la Fusée B-1130 BRUSSELS Tel: +32 (0)2 729 51 51 Fax: +32 (0)2 729 99 84 E-mail: [email protected] Open on 08:00 - 15:00 UTC from Monday to Thursday, incl.

DOCUMENT APPROVAL

The following table identifies all management authorities who have successively approved the present issue of this document.

AUTHORITY NAME AND SIGNATURE DATE

Please make sure that the EATMP Infocentre Reference is present on page ii.

Technical Manager

B. Bakker

Domain Manager

M. Griffin

Head of DAS/ATS

P. Dias


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DOCUMENT CHANGE RECORD

The following table records the complete history of the successive editions of the present document. EDITION NUMBER

EDITION DATE

INFOCENTRE REFERENCE REASON FOR CHANGE PAGES

AFFECTED

1.0 23 Dec 2005 First issue, prepared by Luca Save. all


Edition: 1.0 Released Issue Page v

CONTENTS

DOCUMENT CHARACTERISTICS.............................................................................. ii

DOCUMENT APPROVAL ........................................................................................... iii

DOCUMENT CHANGE RECORD............................................................................... iv

EXECUTIVE SUMMARY.............................................................................................. 1

1. PURPOSE OF THE SURVEY................................................................................ 2

2. SURVEY METHOD ................................................................................................ 3

2.1 Investigation process ................................................................................................................ 3

2.2 On-site Interviews in Military Units............................................................................................ 4

2.3 Web based questionnaire for Military Units .............................................................................. 4

2.4 Survey response rate ................................................................................................................ 5

3. AREAS OF CONCERN FROM THE SPIN SURVEY ............................................ 5

4. AREAS of CONCERN incoporating military issues........................................ 11

4.1 Update and integration of the 14 Areas of Concern ............................................................... 11

4.2 New Areas of concern............................................................................................................. 15

5. Glossary .............................................................................................................. 17


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EXECUTIVE SUMMARY

This report has been produced by Deep Blue under contract to EUROCONTROL (Contract Number C/1.185/00/NB /TRS/018/04/SubtaskA05-02).

The SPIN -Survey of Practices in safety Nets- consisted of four surveys, conducted in 2004, concerning four different aspects of Safety Nets (SNET): ground based safety net implementations; studies and R&D actions; existing practices in the airborne domain; and current industrial capabilities and practices. The Summary Report (EATM Infocentre Reference: 05/02/14-01) presents the results of the four surveys, in particular the 14 identified Areas of Concern.

The 2004 Survey investigated primarily the practices of the 35 ANSPs of the ECAC area and consequently military aspects were not explicitly addressed. It was therefore decided to conduct a complementary survey in 2005: practices in Military ATM comprising a full-scale investigation of current practices related to STCA (Short Term Conflict Alert), MSAW (Minimum Safe Altitude Warning) and APW (Area Proximity Warning) in Military Units. This survey highlighted, amongst others, that most Areas of Concern identified in the previous surveys equally or stronger apply in Military Units.

This report recalls the Areas of Concern from the previous surveys and indicates how they apply in Military Units. The Areas of Concern related to safety nets practices in Military ATM are:

• Lack of common understanding of purpose and policies;

• Need to review regulations and guidance material to overcome discrepancies;

• Lack of common strategies for validation;

• Human Machine Interface issues;

• Lack of common optimization strategies and knowledge of optimization methods;

• Need for consistent implementation of MSAW and APW;

• Need for Civil-Military Interoperability;

• Lack of information and training to controllers;

• Use of CFL in STCA;

• Clarity of organisational roles and management involvement;

• Use of STCA statistics as safety indicator;

• Role of MSAW in Military ATM;

• Role of APW in Military ATM.


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1. PURPOSE OF THE SURVEY

The Survey of Safety Nets Practices in Military ATM extends the SPIN (Survey of Practices in Safety Nets) investigation that was performed in 2004 in the framework of the Safety and Strategic Action Plan (SSAP). The 2004 investigation comprised:

• Survey 1 - Ground based safety net implementations. Full-scale investigation of current practices related to STCA (Short Term Conflict Alert), MSAW (Minimum Safe Altitude Warning) and APW (Area Proximity Warning) in the States of the ECAC Area. This survey highlighted, amongst others, that there are no harmonised or uniform optimisation procedures and validation criteria. In most cases, there is no explicit, overall policy and little or no involvement of Regulatory Authorities.

• Survey 2 - Studies and R&D Actions. Search, selection and analysis of relevant studies and R&D actions concerning ground based SNET. This survey highlighted that there is limited publicly available material to contribute to short-term SNET enhancement actions.

• Survey 3 - Existing practices in the airborne domain. Analysis of relevant aspects of airborne SNET, aimed at considering potentially useful practices for the ground domain. This survey highlighted contrasting practices for airborne SNET.

• Survey 4 - Current industrial capabilities and practices. Investigation of commercial products and services currently available in the domain of ground based SNET. Many products and services are available, but detailed information is not publicly available.

Survey 1 was in particular focused on existing implementations of STCA, MSAW and APW and was conducted in two main steps: the administration of a web-based questionnaire to different stakeholders in 35 ECAC States followed by face-to-face interviews in the ANSP headquarters of 9 selected States.

The main result of the investigation was a list of 14 Areas of Concern (AOC). However, military aspects were not explicitly addressed. It was therefore decided to conduct another survey in 2005:

• Survey 5 – Practices in Military ATM. Full-scale investigation of current practices related to STCA (Short Term Conflict Alert), MSAW (Minimum Safe Altitude Warning) and APW (Area Proximity Warning) in Military Units.

Survey 5 was conducted as a “light weight” repetition of Survey 1. The survey method is described in Chapter 2. Chapter 3 recalls the AOC identified in Survey 1-4 while Chapter 4 describes how these AOC were found to apply to ground-based safety nets in Military Units.


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2. SURVEY METHOD

2.1 Investigation process

Like Survey 1, the Survey of Safety Nets in Military ATM also includes on-site interviews and a web based questionnaire. Both were aimed at collecting sufficient data to understand if the AOC identified by the previous study were also applicable in Military Units or if there was a need to integrate and amend some of them with specific military issues.

The following figure depicts the overall investigation process followed since the previous survey to the present work. The area in grey delimits the contents addressed in the present report.

Areas of Concern updated with Military

Issues

SSAP

Identification of 14

Areas of Concern

Consolidation of 14

Areas of Concern (including

civil/military interoperability)

44 Responses to a web based

questionnaire (from 20 ANSPs out of 35 ECAC States)

On-site interviews in 9 selected

ANSPs

Survey of SNET Practices in Military ATM

On-site interviews in 2 military ANSPs

Responses to a web based questionnaire

from 8 military ANSPs

SPIN Survey of Practices in SNET



2.2 On-site Interviews in Military Units

Two on-site interviews were performed as a preliminary step of the survey to assure a basic understanding of specific military issues and to adapt the web based questionnaire used for civil ANSPs to the military context.

The Military Units selected for the interview have considerably different characteristics. One is a military ACC responsible for the control of an airspace specifically devoted to military operations. The second is an ACC including both civil and military sectors operating in the same airspace.

The first interview was based on a checklist of issues which was previously used for the interviews in civil ANSPs. To assure flexibility, the list was also open to possible new issues identified during the interview. The second interview was then conducted with an adapted checklist incorporating the experience feedback from the first interview.

The list below summarizes the main topics addressed during the interviews:

1. SNET general Policy

2. SNET implementation strategy

3. Setting of SNET Regions and Parameters

4. HMI of the SNET Alerts

5. Monitoring of Performances and Optimisation

6. SNET Verification and Validation

7. Local Instructions

8. SNET related training

9. SNET acceptance by ATCOs

10. Experience with Safety Nets

Every topic was addressed separately for STCA, MSAW and APW.

2.3 Web based questionnaire for Military Units

The web based questionnaire follows the same basic structure of the questionnaire adopted for the civil survey. It is only adapted to fit with specific military issues, also based on the experience from the two on-site interviews. During the survey it was accessible through a secured web server, protected by a password to guarantee the confidentiality of collected information.

The questionnaire is composed of 70 questions, which can be grouped in the following categories:

• Identification of the respondent (3 questions)

• General SNET Policy (3 questions)

• STCA (36 questions)



• APW (20 questions)

• MSAW (5 questions).

Invitations to answer the questionnaire were sent by email to all member of the EUROCONTROL Military Team, with representatives of 27 States in the ECAC area.

2.4 Survey response rate

Reactions to the survey came from 19 States out of the 27 represented in the Military Team. Direct contributions were 10 (including 2 interviews and 8 questionnaires), while the reminder of 9 respondents did not contribute to the survey for the following reasons: no Military ATM present in the country (7 cases), SNET still under design (1 case) and lack of sufficient resources to contribute in the survey timeframe (1 case).The situation is summarized in the table below.

27 States represented

19 States Active reaction

8 States No reaction

10 States Direct contribution

9 States No contribution

2 ANSPs Interview

8 ANSPs Questionnaire

7 ANSPs No Military

ATM

1 ANSP SNET still

under design

1 ANSP No

resources available

Note that 5 of the directly contributing ANSPs have their sectors co-located in civil ATC Units, while the other 5 have pure Military Units.

3. AREAS OF CONCERN FROM THE SPIN SURVEY

This chapter contains a summary of the main output from the 2004 SPIN investigation. Findings are summarized in a list of AOC which identify a potential field of action.

Each AOC is presented in a 2 columns table. The left side column indicates the specific SNET concerned by the AOC, while the right side column provides a short description of the AOC.



1 COMMON VISION ON ‘SNET’ PURPOSES

STCA MSAW

APW

The implementation of SNET in the ECAC Area is based on a variety of different solutions for parameters, HMI, validation and optimization techniques. The differences are related to considerably different policies and reflect the lack of a common vision among the ANSPs, particularly with regard to STCA.

Differences in design solutions are inevitable, due to local operational needs and to particular airspace characteristics. Nevertheless the lack of common definitions and of a shared understanding of SNET purposes does not assure consistent and effective policies. For example some ANSPs declared to intend SNET as systems to support separation assurance, while other ANSPs put more emphasis on the collision avoidance function.

Generally speaking ANSPs with more experience have a limited knowledge of the approaches adopted at different sites, while the less experienced ANSPs have limited opportunities to consider the advantages and disadvantages of the solutions adopted elsewhere. Furthermore, in some ANSPs the STCA is perceived as a purely technical feature of MRT systems and CWPs, with no direct involvement of the management in the definition of implementation policies.

With regard to MSAW and APW –which are less mature than STCA– there is an expectation that a common vision established in a timely manner would help in preventing some of the discrepancies and inconsistencies occurred with the STCA (see also following AOC 7).

2 HARMONIZATION WITHIN AND BETWEEN COUNTRIES

STCA MSAW

APW

The pressure towards standardisation of SNET is substantially limited by both the already existing implementations and the different operational needs at local level, especially for what concern STCA. It is to be noted that differences are present not only between ANSPs, but also within the same ANSP. SNET implementations can vary between one Air Traffic Management Unit and the others in the same country. A potential consequence of the inconsistencies is the dissipation of useful experience feedback and best practices.

Thus there is a need to understand in which cases it is reasonable to have:

- Common standards

- Common system specifications

- Shared guidance material.

While it is still not apparent which level of harmonization is possible to achieve, it is common opinion that standards should not involve design issues.



3 REVIEW OF RELEVANT ‘SNET’ REGULATIONS AND DOCUMENTS

STCA MSAW

APW

There is a need to review currently available regulations and guidance material pertaining to SNET, in order to overcome discrepancies that can potentially impair the definition of well established policies.

A relevant example are the definitions of SNET provided by SRC Policy Document 2 and IFACTA from one side and the definition of STCA and MSAW provided in ICAO Doc 4444 §15.6.2 and 15.6.4 on the other side.

While the first two definitions describe SNET as systems/functions with the sole purpose of avoiding collisions (including both collision with other aircraft and with the terrain), the ICAO Doc 4444 refer to alerts aimed at preventing the infringement of respectively separation minima and minimum safe altitudes.

Despite SNET implementations can reflect more than one of these definitions, it is deemed necessary to clarify the implications of the different approaches and to consider if there is a need to propose modifications to SRC Policy Document and/or to ICAO regulations. Also the definitions provided in EUROCONTROL specifications should be reviewed accordingly.

4 VALIDATION CRITERIA AND VALIDATION PROCESSES

STCA MSAW

APW

There is a lack of common strategies to validate SNET.

In some ANSPs validation is exclusively based on acceptance tests with controllers before making the system operational. In other cases validation is also based on a formalized method to perform validation exercises, i.e. STCA functioning is simulated based on an encounter model allowing a statistical analysis of the alerts. The statistical analysis serves to check if system performances are consistent with the requirements, running a range of different scenarios.

Generally speaking the STCA is perceived as system functioning in an ever-changing environment. Thus well defined performance objectives are rarely identified and it is common that validation processes are not clearly distinguished from optimisation processes.

5 HUMAN MACHINE INTERFACE OF THE ‘STCA’

STCA MSAW

APW

HMI features of the STCA are considerably different at different sites.

Relevant differences include:

- Levels of alerting: single vs multilevel

- Kind of alerting: only visual vs visual and aural

- Kind of visual display: flashing vs coloured alerts

- Addressing of the alerts on CWPs: only to concerned radar controllers, also to planning controller, also to supervisor, also to next way point controller, to all situation pictures irrespective of active filters.

- Possibility to switch of the STCA or to inhibit specific alerts: allowed vs not allowed.

It is generally agreed that standardization should not involve specific HMI design issues, to let the ANSPs identify the solutions that better fit their own operational need and cultural constraints. However most of the ANSPs are interested in understanding characteristics and potential advantages/disadvantages of solutions adopted elsewhere.



6 OPTIMIZATION OF ‘STCA’

STCA MSAW

APW

There is a lack of common methods and sufficient knowledge to optimize STCA performances and achieve an appropriate trade-off between nuisance alerts reduction and anticipated warning time. The following factors where identified among those limiting the definition of adequate optimization strategies:

- Lack of common and agreed definitions of terms like false alerts, nuisance alerts, unnecessary alerts and undesired alerts, etc.

- Lack of a clearly perceived distinction between validation and optimization/tuning processes.

- Limited perception of the operational consequences of a non optimized STCA by ANSPs managers

- Lack of adequate techniques to divide airspaces in different parameter regions and to adapt parameters to different operational constraints.

- Limited perception of nuisance alerts as a real concern by ANSPs still having low traffic levels.

- Lack of sufficient knowledge and/or resources available to perform optimization processes.

7 CONSISTENT IMPLEMENTATION OF ‘MSAW’ AND ‘APW’

STCA MSAW

APW

MSAW and APW are less mature than STCA in terms of knowledge, achieved results and lessons learnt.

Several ANSPs – especially those that are presently facing investments to purchase and/or implement these SNET - are interested in acquiring and sharing information about their implementation, validation and optimisation strategies.

There is an expectation that a common vision on MSAW and APW would help in avoiding some of the errors occurred for STCA.

Another important point raised during the SPIN survey is the need to define Approach Path Monitoring (APM) as a separate SNET, while originally APM function was included under the MSAW umbrella.

8 MANAGEMENT OF INTERACTIONS BETWEEN ‘STCA’ AND ‘TCAS’

STCA MSAW

APW

Despite TCAS TAs and RAs are normally expected to activate as a last barrier, only after the activation of STCA on CWP, several cases have been reported in which STCA alerts are triggered after TCAS. This can happen in TMAs and in particular circumstances, such as high traffic density, holdings, etc. Such behaviour is explained by the functional and technical independence of the two systems, but can result particularly problematic from the controller’s point of view, as it drastically reduce his/her possibility to effectively recover from hazardous situations.

In this respect, a better understanding of interactions between TCAS and STCA in case of separation infringements is deemed beneficial, at least for an appropriate setting of STCA parameters.

Another possibility, currently investigated in R&D initiatives (e.g. FARADS project), is the RA downlink to CWPs. The availability of information concerning TCAS RAs is expected to increase the controller’s situation awareness and to prevent him/her from issuing contradictory or distracting instructions to pilots.



9 CIVIL- MILITARY INTEROPERABILITY

STCA MSAW

APW

A number of factors, including the expected increase of traffic levels, the Single European Sky Initiative and the evolution of ATM concepts (e.g. the ‘Flexible Use of Airspace’ concept) are pushing towards an enhanced cooperation between civil and military sides of the ATM. Ground based SNET (namely STCA and APW) are expected to play a relevant role in assuring a safe interoperability. Thus there is a need to increase the mutual knowledge about SNET policies and implementations on the two sides and to identify specific issues and problems of military Air Traffic Management Units.

10 CONSIDERATION OF ‘SNET’ BY REGULATORS

STCA MSAW

APW

SRC Policy Doc 2 defines SNET as “engineered systems which are designed and operated for the sole purpose of collision avoidance”. In addition it considers “any safety benefits which may be provided by a SNET” as an “additional overlay to that provided by the ATM systems”. Thus it states that SNET should not be considered in the determination of the Target Level of Safety of the ATM system, as defined in ESARR 3 and 4. This approach is not fully agreed in the ATM community and raises a number of questions in the definition of SNET policies:

- Should all SNET (including ground based and airborne SNET) be considered at the same level from a regulatory point of view?

- Should STCA be considered as a mere collision avoidance system, or as function “to assist the controller in maintaining separation between controlled flights” as stated in ICAO DOC 4444.

- Should SNET be excluded from Safety Argument and Safety Cases in the assessment of ATM system?

- What role should the regulators play in the definition of SNET policies?

11 INFORMATION AND TRAINING TO CONTROLLERS

STCA MSAW

APW

ANSPs have considerably different strategies with regard to the provision of information about SNET functioning to ATCOs.

Nearly none of the ANSPs has a specific training for SNET. In addition a large majority of them don’t have specific written instructions relating to STCA and MSAW (as indicated in ICAO Doc 4444 §1.5.6.2.1 and §1.5.6.4.1).

Some of the ANSPs consider very useful that ATCOs are informed about the technical functioning of SNET. For example, motivated explanations of an unexpected behaviour of the STCA are deemed essential for improving ATCO’s confidence in the reliability of the system. However only few cases there is an increasing interest in the improvement of paper/software manuals and of training to include explanations of SNET features.



12 USE OF ‘CLEARED FLIGHT LEVELS’ AS DATA SOURCE FOR ‘STCA’

STCA MSAW

APW

As far as strip-less systems are introduced there is an increasing use of the digital input of Cleared Flight Levels by ATCOs as data source to improve STCA prevision capabilities (and potentially to reduce the number of unnecessary alerts). However the adoption of this feature is still limited for the following reasons:

- Some of the ANSP don’t consider CFL as a reliable data, as there are frequent cases in which ATCOs do not (or cannot) systematically input the CFL.

- Some of the ANSP don’t consider CFL as a reliable data, as the following compliance of the pilot with cleared flight level is not guaranteed.

- Some of the ANSP repute that only the downlink of Executive Flight Levels (what is actually input by pilots) will be a reliable solution in future.

Other ANSPs representatives argue that only a user friendly HMI allows ATCOs to do a systematic use of CFL and thus to provide a reliable data to STCA.

In conclusion advantages and disadvantages of the adoption of CFL for the STCA are still not completely clear.

13 ORGANISATIONAL ROLES AND MANAGEMENT INVOLVEMENT

STCA MSAW

APW

Organisational roles and responsibilities with regard to the adoption and use of SNET are not clear and well defined in some of the ANSPs.

In most of the cases SNET are perceived as a pure technical issue, without a clear involvement of the management in the definition of their implementation policy.

In most of the cases, Safety Managers play a very limited role in the definition of SNET implementation policies. It is still not clear whether their role should be increased in this domain or whether it is better to delegate the function to other organisational roles.

14 USE OF ‘STCA ALERTS RECORD’ AS SAFETY INDICATOR

STCA MSAW

APW

As for AOC 4 and 6, the way STCA alerts are analysed is not homogeneous. Only a few ANSPs make a systematic monitoring of STCA alerts, based on the use of specific tools. These tools help them in deriving information about STCA functioning and can potentially contribute to the assessment of general safety conditions.

In most of the other cases the monitoring is only performed manually, based on the analysis of specific cases. As a matter of fact some ANSPs do not or cannot record STCA alerts and some others have too many false and nuisance alerts to clearly distinguish true and false alerts (see again AOC 4 and 6). In addition there are cases in which the monitoring is limited by Trade Union agreements that do not allow investigating STCA records.

Generally speaking analysis of controllers’ and pilots’ reports and other kinds of analysis not directly triggered by STCA alerts –such as those based on ATM Safety Monitoring Tool (ASMT)- are preferred to specific STCA monitoring. However there is a perception that an improved STCA could be used as a safety indicator, for example in supporting the identification of “hot spots” and in monitoring the effects of changes in equipments and in airspace design.



4. AREAS OF CONCERN INCOPORATING MILITARY ISSUES

4.1 Update and integration of the 14 Areas of Concern

In this chapter the 14 AOC resulting from the 2004 SPIN investigation are confronted with the new data coming from the survey in Military ATM.

Each AOC is categorized as follows:

• Not applicable (the AOC does not apply to Military ATM)

• Information not available (the AOC cannot be verified based on available data)

• Partially confirmed (the AOC is only partially corroborated by the new data)

• Confirmed (the AOC is corroborated by the new data)

• Increased (the AOC is stronger in military ATM than in civil ANSPs).

The categorization of each AOC is reported in the left column of the table, together with the concerned SNET. While the right column of the table describes how the AOC is confronted with new data.

1 COMMON VISION ON ‘SNET’ PURPOSES

INCREASED

STCA MSAW

APW

In Military ATM the lack of a common vision on SNET purposes is stronger than in Civil ATM. Awareness of the importance of ground based SNET is generally low.

In case of co-located sectors, it is common that military sectors have exactly the same systems as civil sectors. While in case of pure Military Units, SNET implementations tend to be perceived as an additional feature of MRT systems, with no specific policy implications and with little involvement of managerial levels.

One case has been reported in which military sectors have exactly the same SNET as civil sectors, except for the opportunity given to the former to switch off SNET visualization on the CWP when convenient.

2 HARMONIZATION WITHIN AND BETWEEN COUNTRIES

INFORMATION NOT AVAILABLE

STCA MSAW

APW

The number of responses is too limited to derive conclusions about standardization levels (see information about the response rate in section 2.4).

However, the responses show that both SNET management strategies and SNET implementations are at least as heterogeneous as in the civil Units.



3 REVIEW OF RELEVANT ‘SNET’ REGULATIONS AND DOCUMENTS

CONFIRMED

STCA MSAW

APW

This AOC applies equally in Military ATM.

Although ICAO rules are not mandatory for OAT, discrepancies between SRC Policy Document 2 and ICAO Doc 4444 §15.6.2 and 15.6.4 are deemed problematic, due to the need for civil/military interoperability and to the co-location of many military sectors with civil sectors.

4 VALIDATION CRITERIA AND VALIDATION PROCESSES

CONFIRMED

STCA MSAW

APW


There is a lack of knowledge and of common strategies to validate SNET.

Only 1 out of 10 respondents declared to perform an analysis of STCA alert rates to perform STCA validation. The majority of respondents only perform acceptance tests with controllers before making the system operational. For some respondents SNET are not mature enough to undergone validation processes.

5 HUMAN MACHINE INTERFACE OF THE ‘STCA’

CONFIRMED

STCA MSAW

APW


HMI features of the STCA are considerably different at different sites.

Examples of differences include:

- Levels of alerting: 3 out of 10 ANSPs use multilevel alerts. The remainder use one level alerts.

- Kind of alerting: 4 out 10 ANSPs use also acoustical alerts while 2 out of 10 declare to have an acoustical alerts system under design. The reminder use only visual alerts.

- Addressing of the alerts on CWPs: 3 out of 10 ANSPs address the alerts to all situation pictures irrespective of active filters, 2 of them to the concerned controllers and to the supervisor, other 2 to the concerned controllers and to the next way point controllers, 3 only to the concerned controllers.

- SNET and specific tracks inhibition: in 1 out of 10 ANSPs ATCOs can switch off the STCA visualization, in a second one ATCOs can manually inhibit specific tracks (preventing the alert), while in a third one ATCOs are only allowed to acknowledge the alert (they stop the flashing, although the alert will remain highlighted). In all the other cases switching off and inhibitions by ATCOS are not allowed.



6 OPTIMIZATION OF STCA

INCREASED

STCA MSAW

APW

The lack of methods to optimize STCA is stronger than in Civil ATM.

The acceptance of STCA by military ATCOs is generally low. At least 4 out of 10 ANSPs consider STCA not very useful due to the particular needs of military operations and to the high rate of nuisance alerts. Among these ANSPs there is one in which STCA is frequently switched off by ATCOs and another one in which the STCA is normally ignored. Nuisance alerts are not considered an issue only in 2 out of 10 cases.

Due to the particular needs of military operations, a typical optimization strategy adopted in Civil ATM (i.e. the definition of multiple parameters regions) is seldom adopted (2 out of 10 cases reported) and only in ANSPs using exactly the same system for civil and military sectors.

Cleared flight levels to reduce nuisance alerts are used only in 2 out of 10 ANSPs, while another solution is the use of “Block Flight Level”, adopted in one Military Unit (see also AOC 12).

Two cases have been reported in which also primary tracks are considered by STCA, due to local operational needs. This feature is often causing nuisance alerts, difficult to accept for controllers.

In 7 out 10 cases formation flights are managed allowing only the formation leader to squawk, in order not to have alerts triggered by the other a/c in the formation. While no special solutions are reported in order to manage air defence intercepts or air to air refuelling (except for the use of STCA Suppression Areas and High Manoeuvring Codes).

7 CONSISTENT IMPLEMENTATION OF ‘MSAW’ AND ‘APW’

PARTIALLY CONFIRMED

STCA MSAW

APW

As for Civil ATM, MSAW and APW are less mature compared to STCA. Only 1 out of the 10 respondents has MSAW fully operational, while other 2 have it under design. Then only 2 respondents out of 10 have APW fully operational, while other 2 have it still under design. However there at least 2 important differences with respect to Civil ATM:

1- There is much less interest in the implementation of MSAW, because of the particular nature of military operations (see also AOC 15).

2- There is much more interest in the implementation of APW, as this system can be a very important support to keep military aircraft inside the appropriate airspace blocks and to help civil aircraft remain out of these airspace block (see also AOC 16).

8 MANAGEMENT OF INTERACTIONS BETWEEN ‘STCA’ AND ‘TCAS’

NOT APPLICABLE

STCA MSAW

APW

The management of interactions between STCA and TCAS can apply only partially in Military ATM. In most of the cases military aircraft are not equipped with TCAS and not subject to ICAO regulations.



9 CIVIL- MILITARY INTEROPERABILITY

CONFIRMED

STCA MSAW

APW

This AOC obviously apply equally in Military ATM. It was the main reason triggering the present survey.

The understanding and management of civil/military interoperability is of paramount importance especially for the optimization of STCA and APW in all the operational contexts characterized by interfaces between OAT and GAT.

10 CONSIDERATION OF ‘SNET’ BY REGULATORS

INFORMATION NOT AVAILABLE

STCA MSAW

APW

This aspect was beyond the scope of the survey.

11 INFORMATION AND TRAINING TO CONTROLLERS

CONFIRMED

STCA MSAW

APW

This AOC applies also in Military ATM.

8 out of 10 respondents consider SNET related training as part of the normal training. While 2 out 10 have a specific training program.

7 out of 10 respondents don’t have specific written instructions related to SNET, while 3 out 10 have written instructions not compliant with ICAO Doc 4444 §1.5.6.2.1 and §1.5.6.4.1.

12 USE OF ‘CLEARED FLIGHT LEVELS’ AS DATA SOURCE FOR ‘STCA’

CONFIRMED

STCA MSAW

APM APW


Cleared flight levels (CFL) to reduce nuisance alerts are used only by 2 out of 10 respondents. In another case CFL are integrated with Block Flight Levels (BFL), which consist of a lower and an upper Flight Level to be processed for the STCA. This solution appears to fit with the particular needs of certain military operations, in which aircraft are not expected to fly in a specific level, but in a defined band of different levels.

However, as in Civil ATM, advantages and disadvantages of the adoption of CFL and BFL are still not completely clear.



13 ORGANISATIONAL ROLES AND MANAGEMENT INVOLVEMENT

ICREASED

STCA MSAW

APW

This AOC applies equally in Military ATM. However, in this case awareness of the importance of SNET appears to be lower.

In most cases organisational roles and responsibilities with regard to the adoption and use of SNET are not clear and well defined. In case of co-located civil/military sectors, the responsibility for SNET is generally delegated to engineering department of the civil ANSP, without a specific consideration of military issues. Generally speaking (as for AOC 1) SNET are perceived as a pure technical issue, without a real involvement of management.

Safety Management functions have been recently established and don’t appear to be mature enough for a real commitment to SNET policies. In addition, as for civil ANSPs, it is still not clear whether Safety Manager’s role is the one that better fits with this kind of responsibility.

14 USE OF ‘STCA ALERTS RECORD’ AS SAFETY INDICATOR

PARTIALLY CONFIRMED

STCA MSAW

APW

This AOC applies equally to military ATM.

One out of 10 ASPs performs a systematic analysis of STCA alerts (although the analysis is performed by the civil part of the organization and military sectors are co-located with civil sectors). However, in the case of Military ATM it is even less clear whether an analysis of STCA alerts could play a role as safety indicator, due to the specific operational nature of Military ATM.

In most cases there are still too many optimizational issues to be addressed in order to have valuable data from the analysis of alert rates.

4.2 New Areas of concern

This subsection presents 2 new AOC not identified by the previous study with relevance for military ASPs.

15 ‘MSAW’ ROLE IN MILITARY ‘ATM’

STCA MSAW

APW

One out of the 10 respondents has MSAW fully operational, while 2 have it under design. Two respondents declared that they are planning to implement it in future (one of them is an ANSP with co-located civil and military sectors). However the 3 ANSPs currently equipped with MSAW consider this SNET not very useful, based on the particular needs of military operations.

Although 1 ANSP proposed to define a “Different minimum safety altitude for military aircrafts”, it is questionable whether it is possible to set the MSAW function to fit with military operational constraints. Military aircraft are generally allowed to fly close to the terrain and the responsibility for avoiding collisions with terrain is completely up to pilots. Thus it is common that ATCOs controlling military aircraft simply ignore MSAW alerts, questioning the actual role of MSAW in Military ATM.



16 ‘APW’ ROLE IN MILITARY ‘ATM’

STCA MSAW

APW

Two out of the 10 respondents have APW fully operational, while 4 have it still under design. Two respondents declared that they are planning to implement it in the future.

One respondent considered APW a fundamental function in case of activation of Temporary Restricted Areas (TRA). However, the observation revealed that in those circumstances APW is not only used as a mere SNET, but also as a monitoring tool. All aircraft involved in an exercise inside a TRA generate at least one alert when entering the TRA and a second alert when exiting it. Thus from the military ATCO’s point of view the function becomes also a mean to monitor the beginning and the end of an exercise in a TRA.

Despite the original purpose of APW as a SNET is confirmed (i.e. to alert controllers when an aircraft is currently in a danger area, or is at risk of entering a danger area) also the operational implications of the use as a monitoring tool should be better understood.


Edition Number: 1.0 Released Issue Page 17

5. GLOSSARY

ACAS Airborne Collision Avoidance System

ACC Airspace Control Center

ANSP Air Navigation Service Provider

AOC Area of Concern

APW Area Proximity Warning

ASMT Automatic Safety Monitoring Tools

ATM Air Traffic Management

ATCO Air Traffic Controller

BFL Block Flight Level

CFL Cleared Flight Level

ECAC European Civil Aviation Conference

GAT General Air Traffic

HMI Human Machine Interface

ICAO International Civil Aviation Organisation

MSAW Minimum Safe Altitude Warning

OAT Operational Air Traffic

RA Resolution Advisory

SNET Safety Net

SPIN Survey of Practices In safety Nets

SRC Safety Requirements Commission

SSR Secondary Surveillance Radar

STCA Short Term Conflict Alert

TCAS Traffic alert and Collision Avoidance System

TMA Terminal Control Area

TRA Temporary Restricted Area

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Survey of Safety Nets Practices in Military ATM - … · Survey of Safety Nets Practices in Military ATM ... The Survey of Safety Nets Practices in Military ATM extends the SPIN