Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. 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:
The 3 supporting blocks [installed on hydraulic lines] were made of Teflon, which is unsuitable material for this application. Excessive wear of the blocks was discovered on numerous aircraft, as well as several cases of chafing between the loosely supported tubes. In one case, hydraulic fluid was lost due to fatigue failure of an inadequately supported tube. Loss of hydraulic fluid causes subsequent multiple failures of hydraulically operated systems.
Multiple failures of hydraulically operated systems (for the flight air brake actuators, brake system, right thrust reverser, etc.) could result in reduced controllability of the airplane.The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.