Summary
We are revising an earlier NPRM for the products listed above. This action revises the earlier NPRM by expanding the scope. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated 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:
Periodic operational check of the firewall hydraulic shutoff valves, made during routine maintenance, has revealed that the failure rate of that component is significantly higher than expected. Such a dormant failure, when combined with further possible failures, such as engine fire, may lead to an unacceptable reduction of safety margins.
The unsafe condition is failure of the firewall hydraulic shutoff valve, which, in combination with an engine fire, could result in loss of hydraulic pressure or spread of an engine fire beyond the firewall. The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.