*3.1. Taxonomy Inter-Rater Concordance*

Altman [18] categorises levels of agreemen<sup>t</sup> for Cohen's Kappa as shown in Table 3.


**Table 3.** Levels of agreement, adapted from Altman [18].

The Kappa value for this study's inter-rater concordance, derived using IBM SPSS Statistical Software, is given in Table 4. The derived agreemen<sup>t</sup> statistics are provided in Table 5.


inter-rater

concordance.

Determined

**Table5.**Derivedagreemen<sup>t</sup> statisticsacrossalllevels.


This shows a good to very good strength of agreemen<sup>t</sup> between the researcher and SME when utilising the MxFACS taxonomy and consequently indicates a high level of rigour for this qualitative research.

### *3.2. Distribution of Serious Incidents and Accidents for 2003–2017*

**Table 4.**

From the data collection process, 112 accidents and serious incidents were identified as maintenance-related for 2003–2017. The global distribution for these events can be seen in Figure 4a,b.

The results shown in Figure 4a vary quite significantly from the maintenance threat levels given by IATA [19]. IATA [20], do however highlight that air accident investigations require greater cooperation on global standards; of around 1000 accidents over the last ten years, accident reports are only available for approximately 300. They state that of those reports, many contain insufficient information or lack rigorous analysis [20]. Consequently, this may provide some justification for the disparity.

(**a**) 

(**b**) 

**Figure 4.** (**a**) Number of serious incidents and accidents identified for 2003–2017. (**b**) Number of serious incidents and accidents (2003–2017) by operator location.

A comparison of the number of EASA Member State events identified for the same time period as EASA's 2014–2017 Annual Safety Reviews (ASR) is shown in Table 6.

**Table 6.** Comparison of study data with EASA ASRs.


A plausible explanation for this disagreement may be due to interpretation of "CAT" used within the studies. EASA's ASR focus on CAT aeroplane airline operations for aircraft greater than 5700 Kg maximum take-off weight (MTOW), which they describe as covering "the bulk of the commercial

air transport activity" [7]. Comparatively, this study analysed events for any flight which could be acknowledged as CAT under Commission Regulation (EU) no. 965/2012, regardless of number of passengers, aircraft type, or MTOW.
