Review Issues Regarding ATC Systems Capability to Monitor Relevant Controller Intervention Buffer (CIB) Parameters

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Review Issues Regarding ATC Systems Capability to Monitor Relevant Controller Intervention Buffer (CIB) Parameters

41TH ANNUAL CONFERENCE, Cancun, Mexico, 15-19 April 2002

WP No. 87

Review Issues Regarding ATC Systems Capability to Monitor Relevant Controller Intervention Buffer (CIB) Parameters

Presented by SC1

Introduction

1.1 WP 82/2001 presented by SC1 at Geneva reviewed the concept of Controller Intervention Buffer as it relates to the development and application of ATC separation standards and procedures.

1.2 After discussion of the contents of the paper, Committee B at conference recommended the adoption of the following IFATCA policy:

  • The Controller Intervention Buffer be defined as:
    • The time required for the Air Traffic Controller to intervene ensuring that a collision would be averted in the event that a separation standard being applied breaks down. This will include an allowance;
      • to recognize the ‘blunder’,
      • to formulate a solution,
      • to convey instructions to the pilot,
      • for the pilot to react and cause the aircraft to achieve the required change of trajectory.
  • A Controller Intervention Buffer should be included in the development and specification of any separation minima where controller intervention is used as a risk mitigator.
  • All of the parameters used to determine the Controller Intervention Buffer should be part of the documentation of any such separation minima.

1.3 The paper also proposed an additional clause for inclusion in the policy:

ATC systems should be developed with the capability to monitor relevant CIB parameters and warn controllers when they fall outside the values used in determining separation standards in use so that alternative standards can be applied.

This clause was not included in the policy recommendation and the questions, which arose during discussion, were referred to SC1 for further work.

1.4 Discussion within SC1 has confirmed that the reference to the Controller Intervention Buffer in the above clause should in fact have been to the Controller Intervention Capability.

1.5 The purpose of this paper is to clarify the relationship between Controller Intervention Buffer (CIB) and Controller Intervention Capability (CIC), to discuss how each of these attributes relates to ATC system performance and to submit a revised final clause of the policy on CIB/CIC for consideration.

Discussion

2.1 The need for IFATCA to consider these issues first arose as the ICAO SASP (formally RGCSP) used the terms Controller Intervention Buffer/Capability to refer simply to the communications capability and performance required to support particular separation standards. This in the absence of a clear definition of the concept of Required Communications Performance (RCP).

2.2 The CIB as so far defined in previous SC1 work, does not refer solely to the Controller as an individual but rather to the ATC system of which the Controller is a part. The characteristics of the ATC system as a whole define the Controller intervention Capability (CIC).

2.3 Contrary to comments made in relation to the Geneva paper the concept of the CIB/CIC should not be considered an attempt to set performance standards for individual controllers. Rather it seeks to define the capabilities of the ATC system as a whole.

2.4 In the same way that the RNP concept provides a navigation system performance parameter upon which separations and procedures can be predicated, the CIB could be developed into an ATC system performance parameter or standard with a similar purpose.

2.5 Taking the RNP analogy a little further it might be possible to express the CIB as the maximum length of the controller intervention time within a given confidence interval.

2.6 In seeking to define CIC it is worth returning to the work referred to in the Geneva paper (WP 82/2001) here, Dr Anderson (Dr David Anderson – An extended methodology for ADS longitudinal separation standards. RGCSP10 WP/7 May 2000) refers to the Controller Intervention buffer primarily in terms of communication turnaround time but also makes allowances for screen update, message composition and transit, pilot response and aircraft inertia.

2.7 If we consider an ATC system being used to apply the separations being proposed in this work then the attributes of that system that ensure that controller intervention is possible and effective within the CIB specified in the standard could be said to make up the Controller Intervention Capability (CIC).

2.8 As the title of this paper suggests, the problem is then to determine how such a parameter can be measured, monitored and maintained in any given ATC system. Arguably the problem is essentially one of Quality Assurance and breaks down into two main areas:

  • system design and implementation; and
  • system maintenance.

2.9 Each of these areas can be further subdivided into technical and human factors areas.

2.10 Human Factor elements will necessarily be estimates based the conflict recognition and reaction times of properly qualified controllers operating as part of the system under measurement. Quality assurance in these areas should be based on such things as:

  • Training, experience and qualification including familiarisation and recency requirements
  • Medical requirements
  • Working environment including duty hours provisions
  • Performance monitoring and support. Again it is important to emphasise that real time performance monitoring or on shift supervision will not provide a dynamic measure of the CIC but will simply function as one quality assurance element.

2.11 Technical elements will include all of the hardware aspects which may influence the extent of the CIB, such as:

  • Surveillance system characteristics and performance
  • Communications system characteristics and performance
  • Controller interface which may include specific tools such as:
  • Cleared Level Adherence Monitoring (CLAM)
  • Route Adherence Monitoring (RAM)
  • Danger Area Infringement Warning (DAIW)
  • Short Term Conflict Alert (STCA)
  • Flight Plan Conflict Probe (FPCP)
  • Minimum Safe Altitude Warning (MSAW)
  • Deviation Alerts (PRM)

2.12 In most cases the contribution of elements or groups of elements to the CIC could not be directly measured. Credible estimates will need to be derived using appropriate simulation or modelling techniques. The development of the Precision Runway Monitor system (PRM, Precision Runway Monitor Demonstration Report DOT/FAA/RD-91/5 Feb 1991) is a good example of this process.

2.13 Depending on the criticality of an individual ATC system element to the CIC required for the application of a particular standard, it may be necessary to separately estimate the contribution of those elements so that degraded modes of ATC system operation can be appropriately responded to.

Conclusions

3.1 A definition for the Controller Intervention Buffer (CIB) in relation to the formulation of separation standards has previously been proposed.

3.2 The need for a CIB to be included in the specification of new separations standards that rely on controller intervention as a risk mitigator has been accepted.

3.3 It follows that if a certain CIB is allowed for in a separation standard then there should be some means to provide assurance that the ATC system in use in applying that standard is capable of performing consistently within that CIB.

3.4 This requires an understanding of the Controller Intervention Capability (CIC) of ATC systems. In some circumstances (e.g. PRM) it will be necessary to provide real time monitoring of some of the elements that contribute to the CIC.

Recommendations

It is recommended that the current policy on CIC/CIB be amended to include the following additional clause:

4.1 ATC systems should be developed with the capability to monitor relevant Controller Intervention Capability (CIC) parameters and warn controllers when they fall outside the values used in determining separation standards in use so that alternative standards can be applied.

Last Update: September 29, 2020  

March 14, 2020   245   Jean-Francois Lepage    2002    

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