Summary

Introduction

Discussion

2.1 IFATCA Policy on Mixed Mode Operations (MMO)

2.1.1 The Policy on MMO was developed to enable Member Associations (MAs) to cope with change in the dynamic environment in which Air Traffic Control (ATC) has ended up. Controllers more often are working in an environment with multiple surveillance technologies, multiple communication means and multiple navigation methods and accuracies.

2.1.2 The Policy consists of four statements, each with its own function.

2.1.3 The first Policy Statement is a definition, which is required to clearly describe what MMO are.

2.1.4 The second Policy Statement is to give MAs guidance how to deal with existing MMO.

2.1.5 The third statement is created to give guidance to MAs in which way new MMO should be avoided.

2.1.6 The last Statement clearly lays out under which conditions MMO are acceptable if these cannot be avoided. This includes assessing what needs to be done in order to ensure that the individual change is considered on a system-wide bases.

2.2 IFATCA Policy on Intrinsic and Tactical Safety

2.2.1 Intrinsic safety is defined as:

2.2.2 Tactical safety is defined as:

2.2.3 IFATCA Policy in relation to intrinsic safety and airport and airspace design is:

2.2.4 The Policy on MMO is based on the above definitions of intrinsic- and tactical safety.

2.3 IFATCA Policy on Mode S

2.3.1 Current Policy on Mode S contains the following statement;

2.3.2 First of all, the MMO in this Policy Statement refers to the combination of Mode S and other surveillance sources in one area of controller responsibility, with different procedures for ATC. Therewith it fits in the definition and is considered as MMO.

2.3.3 Let us consider the introduction of Mode S in an environment where other surveillance is already in use. In this case the second Policy Statement on MMO is applicable:

If MMO is avoided by the creation of intrinsically safe solutions, then there also is no need for simulations and training for all concerned.

2.3.4 Then we consider a situation in which the implementation of Mode S as additional surveillance next to e.g. Secondary Surveillance Radar (SSR) has taken place and the MMO already is operational. In this case the following two Policy Statements on MMO are valid:

Firstly and ideally, efforts must be undertaken to eliminate the MMO. This could be done by eliminating the difference in procedures, and is the easiest solution to ATC.

If the ideal solution cannot be implemented and therefore MMO cannot be avoided, then assessment must take place to avoid the situation in which the controller’s workload is increased to an unacceptable level. Part of this assessment can be simulations and training, but there are other ways to manage this workload e.g. airspace capacity limitations and/or system support. Policy on MMO covers a greater range of solutions, but certainly includes simulations and training.

2.3.5 IFATCA Policy on MMO is much broader and certainly covers the requirement mentioned in the above Mode S Policy Statement. The latter is therefore recommended for deletion.

2.4 IFATCA Policy on Mixing Data Link Equipages

2.4.1 Policy on mixing data link equipages consists of two Policy Statements. The first is as follows;

2.4.1.1 The use of more than one operationally disparate data link system in any unit of airspace is only considered MMO if there are different procedures associated with each of these data link systems.

2.4.1.2 The first part of the statement is very restrictive and does not allow for multiple data link system in on unit of airspace at all. This appears to contradict the Policy on MMO, where a more pragmatic and realistic approach is taken. The above data link statement needs to be amended or deleted in light of this, more recent, MMO Policy.

2.4.1.3 Let us consider an operational environment in which more than one operationally data link system are in use in any unit of airspace, e.g. the use of Future Air Navigation System (FANS)-1/A and Aeronautical Telecommunications Network (ATN) in a single unit of airspace controller by Maastricht Upper Area Control Centre (MUAC). The data link Policy Statement above simply considers this situation unacceptable.

The MMO Policy considers such an environment differently. There can only be MMO if the controller has to apply different procedures due to variances in characteristics of airspace users. In the above example this would mean that the controller has to use different message sets to communicate to the different data link equipages. But, in the MUAC example this is not the case, as the controller uses a single button for a clearance, while the ‘translation’ to the right datalink message set is done within the system and without any action (or even consideration) by the controller. This is an example with mixed equipage but without MMO.

2.4.1.4 The MMO Policy implies that the use of more than one operationally disparate data link system is acceptable as long as either intrinsically safe solutions are found (the MUAC example) or if the workload is not increased to an unacceptable level. Either way the MMO Policy covers the data link Policy Statement and provides more flexibility and guidance.

2.4.1.5 The second part of the Policy Statement clearly highlights the need for a functionally identical interface in case of aircraft equipped with multiple types of data link functionalities. This would then mean that there would be no different procedures for ATC, therewith avoiding MMO. This would be a perfect example of the third MMO Policy Statement in practice:

The intrinsically safe solution in this example is the fact that the presentation and the procedures are the same, regardless the equipage of the aircraft. This second part of the Policy Statement is covered by MMO Policy.

2.4.1.6 The first part of the Policy on Mixing Data Link Equipages is completely covered by MMO Policy and is therefore recommended for deletion.

2.4.2 The second Policy Statement on Mixing Data Link Equipages is as follows;

2.4.2.1 This Policy Statement is considered in two parts. The first part “In addition to the interface presented to the controller, procedures and systems events must be operationally identical…” simply states the same as the following MMO Policy Statements:

An intrinsically safe solution is created by creating operational identical procedures, interface and system events. This is therefore considered a duplication of the MMO Policy.

2.4.2.2 The second part of the Policy Statement reads;

This states that MMO are acceptable provided that safety and controller workload are not adversely impacted. The relevant MMO Policy Statement reads;

The dissimilar implementation refers to a mixed mode operation, and according MMO Policy this can only be done provided that the controller workload is not increased to an unacceptable level. The only thing not directly covered if the MMO Policy Statement is compared to the data link Policy Statement is the part about safety. This is not separately addressed in the MMO Policy, as safety must be managed by a safety management system (SMS) that has been developed in accordance with ICAO rules and regulations. Part of this SMS is a safety assessment that must ensure that appropriate safety levels are met.

2.4.2.3 As a conclusion of the above arguments, the second Policy Statement on Mixing Data Link Equipages is also recommended for deletion.

2.5 IFATCA Policy on New Technology Approach & Landing Aids

2.5.1 The following relevant Policy Statement can be found in the IFATCA Technical and Professional Manual under New Technology Approach & Landing Aids:

2.5.2 First of all, reductions in spacing can only be undertaken if the new operation is proven to be safe. Safety must be demonstrated via appropriate assessments and managed in an SMS.

2.5.3 Secondly, the following is stated in the MMO Policy:

The Policy statement on New Technology Approach & Landing Aids points out the need to demonstrate safety when any MMO is introduced. Safety in general needs to be demonstrated when new operations are introduced, as indicated above in 2.5.2. This also applies to the introduction of any MMO. However, in order to stress the need to prove that the workload does not increase to an unacceptable level, the MMO Policy goes further and nevertheless stresses the need for assessment of complexity.

2.5.4 Thirdly, IFATCA Policy on New Technology Approach & Landing Aids makes reference to “any remedial measures identified must be carried out”. These remedial measures are the same as mitigating actions, as used in the ICAO SMS. These mitigating actions are part of the demonstration of safety, and safety cannot be demonstrated if those remedial measures are not carried out. This part of the Policy Statement appears to be redundant on its own.

2.5.5 Both ICAO rules and regulations on SMS, and IFATCA MMO Policy indicate that the above Policy Statement on New Technology Approach & Landing Aids is redundant and therefore recommended for deleted.

Conclusions

Recommendations

It is recommended that;

4.1  IFATCA Policy on page 3 2 1 6 of the IFATCA Technical and Professional Manual:

“Where Mixed Mode operations are conducted simulations and training must be provided to all concerned.”

is deleted.

4.2  IFATCA Policy on page 3 2 1 14 of the IFATCA Technical and Professional Manual:

“Controllers must not be required to utilize more than one operationally disparate Datalink system in any unit of airspace. If aircraft equipped with more than one type of Datalink functionality are operating in the same airspace, the interface presented to the controller must be functionally identical.

In addition to the interface presented to the controller, procedures and systems events must be operationally identical except where an operational advantage can be achieved by dissimilar implementations and where there is no adverse impact on safety or controller / pilot workload.”

Is deleted.

4.3  IFATCA Policy on page 3 2 2 12 of the IFATCA Technical and Professional Manual:

“A safety assessment should be carried out before any mixed mode operations or reductions in spacing are undertaken and any remedial measures identified must be carried out.”

Is deleted.