On 22 June 2017, the engine manufacturer released service bulletin SB 72-0531 to all operators of CT7-5A2/9B/-9B1/-9B2 series engines. The SB applied to all PGBs that had accumulated over 30,000 hours’ time-in-service if the PGB main propeller shaft had not been replaced within 10,000 hours.
The SB was focused on the hub flange region and required an inspection for cracking, corrosion and wear damage using both detailed visual and non-destructive methods. The following compliance timeframes were recommended for operators to follow:
- for PGBs that had accumulated over 46,000 hours service, compliance should be within one month, but before accumulating an additional of 150 flight hours
- for PGBs that had accumulated between 40,000 and 46,000 hours, compliance should be within four months, but before accumulating an additional 500 flight hours
- for PGBs that had accumulated between 30,000 and 40,000 hours, compliance should be within eight months, but before accumulating an additional 1,000 flight hours.
At the time of the release of this report, there had been six PGB shaft rejections as a result of the inspections in accordance with SB 72-0531. The rejections were related to corrosion and fretting around the dowel pin holes and the face of the flange. There were no reports of any cracking on any of the inspected shafts.