*3.4. Level 2—System*/*Component Failure*

When coding the dataset at Level 2, 112 events were coded at the system/componen<sup>t</sup> level, as demonstrated by Figure 6.

**Figure 6.** Level 2 top level system/componen<sup>t</sup> failures.

Inevitably, due to differing taxonomies, it is not possible to directly compare the study's findings with previous research. However, when looking at similarities between the results of the UK CAA [2,3], considerable homogeneity exists. In both UK CAA [2,3] studies, powerplant, landing gear, and flight controls are respectively ranked as the second to fourth most populous areas for maintenance error. These three systems are ranked in the same order, but as the first to third most coded, within the top-level coding for MxFACS Level 2 (the 'engine' category can be used interchangeably with 'powerplant').

Given that the CAA studies were of low-level occurrences identified in MORs, and this comparison evidences the trend continuing to permeate through to the higher-level serious incidents and accidents, these three systems can be said to be of continuing significance from 1996 through to present day. Without further research into the targeted actions of maintenance organisations, it is not possible to postulate whether or not this trend continuation is due to inattention to this area of aircraft maintenance. It does however highlight key areas for regulators to target in their risk identification and assessment processes and when proposing oversight measures.

A plausible explanation for equipment and furnishings not attracting a higher frequency of coding within the findings of this study is the severity of the events analysed. In the analysis of low-level, low-severity MORs, it is understandable that frequent occurrences involving the equipment and furnishings listed in ATA 25 will arise. It would, however, be rare for such events to propagate into a serious enough outcome for a serious incident, or even accident, to transpire. Thus, one can expect to see a significantly lower number of occurrences related to ATA 25 within this study.

After identifying the initial event type for each occurrence, more detailed coding of the nature of these events was undertaken. The loss of control events a ffiliated with 'flight controls' can be seen as the third-highest ranking event type. This area is identified as of high risk by the UK CAA [2] and EASA [4], so this prevalence within the dataset therefore indicates a high frequency of event for a high-risk event.
