4.2.4. Occurrence Category

Any occurrence category that resulted in less than 5% of the total were grouped into an 'other' category. The results showing the associated occurrence categories in Figure 4 are not surprising, with system component failure non-powerplant (SCF-NP) the most common, followed by system component failure powerplant (SCF-PP). While in the ICAO official accident statistics SCF are common, they are more common in accidents with maintenance contributions. The increase in SCF occurrences is balanced by slightly less than expected abnormal runway contact (ARC) and runway excursions (RE); more significant is the lack of 'other' for accidents with maintenance contributions, and the fact that 'other' for ICAO official accidents includes turbulence (TURB) which is second most common cause in the ICAO official accident statistics.

**Figure 4.** Distribution of occurrence categories for accidents with maintenance contributions.
