Get ready folks, this is about to get issued. Seems to affect most/all E4 Series engines.
Occurrences of E4 series engines have been reported recently. Investigation of the occurrences has shown in some cases the failure of one inner main bearing screw. Subsequent investigations have determined that certain batches of inner main bearing screws were produced at the lower end of the material strength tolerance for Class 8.8 screws. Depending on the magnitude of the screw’s strength properties, the potential for screw failure, leading to engine failure, exists in cases where abnormal operating conditions are experienced such as fuel quality issues or significant deviations from the fuel system requirements. To address this possible unsafe condition, this Service Bulletin requires the replacement of the inner main bearing screws, with screws having highest safety factor, to be completed within the timeframe specified in §1.6.
Table 1 engines:
A single ferry flight to the next maintenance station to meet the requirements of this service bulletin is allowed. The maximum flight duration is 3 hours and is limited to VFR condition.
Table 2 engines
Before accumulating 300 Flight Hours or with the next scheduled maintenance action, whichever occurs first
Labour effort: 8 hours for main bearing screws replacement according to WI-MSB-E4-042
