The company further contends that there have been more than 1,200 similar head-to-barrel failures in 520/550 cylinders manufactured by other production approval holders, but FAA has not taken action in those cases.
FAA is proposing initial and repetitive inspections, replacement of cracked cylinders and replacement of cylinder assemblies at reduced times-in-service. It would further prohibit installation of the affected assemblies into any engine.
The proposed AD would break the affected cylinders into two groups based on Serial Number (S/N): SN 1-33696 (Group A) and S/N 33697-61176. (Group B). The proposal would require removing Group A cylinder assemblies from service within 25 hr. of the effective date if the operating hours are either fewer than 500 hr. or more than 1,000 hr. Group B cylinder assemblies with 1,000 or more operating hours would need replacement within 25 operating hours following the effective date of the AD.
The proposed AD would require repetitive visual inspections, compression tests and leak checks for cracks on Group A assemblies with between 500-1,000 operating hours and on Group B assemblies with fewer than 1,000 hr.
The proposed AD further would bar installation of the affected assemblies onto any engines, and calls for reporting the removed assemblies to FAA.
FAA is accepting comments on the AD through Oct. 11.