History of the nuisance alert problem in the studied context

straightforward in complex, high-consequence organisations. Organisations may develop different views about the specific hazard and develop their response accordingly. To support this point it is useful to review the main aspects of the history of the nuisance alert problem that have emerged from the analysis presented in the previous section. 1. First, the evidence collected in this study shows that the MSAW-related nuisance alert

problem could not be analysed as an individual problem, as expected at the beginning of the study: its trajectory was strictly related to what has been classified as the “controller lack-of-response” concern, i.e., the tendency by controllers to neglect a reliable alert generated by the MSAW. The first, initial analysis (§ 5.3.1) suggested this latter was the main concern that the NTSB noticed regarding the use of the alarm, as this concerned recurred across five safety letters. At the same time the issue of nuisance alerts appeared to be debated as a sub-item in the context of this concern. In particular, it was considered as a contributory cause to this concern together with

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issues in the areas of alarm HMI design and response procedures, as shown by the evidence presented under section 5.3.2.

2. Second, the first NTSB safety recommendation addressing the nuisance alert problem was issued in 2006, after nearly thirty years of operational life of the alarm (§ 5.3.2). Up to that year the majority of the NTSB efforts to address the lack-of-response problem focused on requesting changes directed (i) at modifying the MSAW HMI design (10 safety recommendations=77%) and (ii) the procedure defining the response to the alert (2 safety recommendations=15%)—both areas encountering some resistance by the FAA. It is in 2006 that the NTSB acknowledged the (primary) contributory role of the nuisance alert to the lack-of-response problem.

3. From a safety perspective, this finding is somewhat surprising because it would suggest that the NTSB neglected the nuisance alert problem up to that year. However, the subsequent analysis of the specific changes contrasted by the FAA (§ 5.3.3) showed this was not the case:

o NTSB’s mentions of the problem were found in 1981, 1984, and 1990; however, in these years the problem was not translated in a corresponding nuisance-alert specific safety recommendation. It was mentioned, instead, as a justification for another change to the FAA: disambiguating between the MSAW and CA aural alerts (i.e., RC1). This was the case because to the NTSB, this design change would have increased the ability of the aural alerts of both systems to attract the attention of controllers towards the specific risk the alarms were intended to avoid. The reason was that controllers were found to be exposed to nuisance alerts on continual basis, and a more salient aural alert would have been more attention capturing.

o In turn RC1 received a negative response by the FAA. To the latter, differentiating the aural alerts would have not enhanced the alerting sequence envisaged for the MSAW (and the CA): both the MSAW and CA aural alerts functioned only as attention grabber; it was the visual alert—displayed on the radar display—that provided information about the type and the entity of the danger. In short, when hearing the aural alert (general alert), controllers had then to check the visual alert (informative alert). To the FAA this envisaged alerting sequence would have not been improved by a more informative aural alert: after hearing it, the controller’s check of the visual alert was still needed.

Chapter 5. Study 1 results

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4. It has to be noted that the NTSB (i) recognition of existence of the nuisance alert problem, noted in relation to RC1 (mentioned here above), contrasts with the recognition of (ii) the MSAW as a reliable system, noted by the agency in relation to RC7. This latter assumption was used as part of the argument which justified the NTSB request to change existing regulations in order to make more mandatory for controllers the transmission of the alert to the pilot (§ 5.3.3.2). The two positions seems incompatible because the same system, in principle, cannot be both seen as reliable and an unreliable at the same time.

To summarise, up to 2006 two main findings have emerged with the history of the nuisance alert: first, the problem of nuisance alert was known, however not seen as an individual target for improvement by the NTSB, but as a justification for a change— disambiguating between the MSAW and CA aural alert alerts—aimed at solving another problem, the “controllers’ lack of response” concern. This was the main issue with the MSAW (according to the NTSB), not the nuisance alert. In turn, this change turned out to be highly contrasted by the FAA.

Second, the NTSB seemed to maintain a contradicting position about the nuisance alert problem: while recognizing it as a justification for RC1, the agency appeared to neglect it in order to justify RC7. With the available data, it is not possible to explain this contradiction and why and how the NTSB came to realise the importance of treating the nuisance alert problem a standalone problem. However, for the broader objective of the thesis—the development of a framework of organisational precursors to HAI issues—the history of the nuisance alert problem in the US is important because it shows that interpreting the significance of a HAI issue is not necessarily an easy endeavour in safety- critical service provider organisations. While the nature and the significance of the problem may be relatively simple when seen from the perspective of the front-end practitioners that uses the concerned automated system, for stakeholders at higher organisational levels the same problem may turn into an ambiguous (and contrasted) issue—as it happened in the case reported here.

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