Summary
This supplemental NPRM revises an earlier proposed airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
During manufacture of high-pressure (HP) compressor stage 1 discs, a small number of parts have been rejected due to a machining defect that was found during inspection. Analysis of the possibility of less severe examples having been undetected and passed into service has concluded that action is required to reduce the risk of failure. It was therefore necessary to reduce the life limit.
The HP compressor stage 1 disc is part of the HP compressor stage 1-4 shaft, part number (P/N) FK32580. We are proposing this AD to prevent failure of the HP compressor stage 1 disc, uncontained engine failure, and damage to the airplane.