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:
In the past, some operators have reported difficulties to pressurise the hydraulic reservoirs, due to leakage of the Crissair reservoir air pressurisation check valves. * * * The leakage of the check valves was caused by an incorrect spring material. The affected Crissair check valves * * * were then replaced with improved check valves P/N [part number] 2S2794-1 * * *.
More recently, similar issues were again reported on aeroplanes with Crissair check valves P/N 2S2794-1 installed. The investigations * * * have shown that a spring, mounted inside the valve, does not meet the Airbus type design specifications.
This situation, if notcorrected, can cause hydraulic system functional degradation, possibly resulting in reduced control of the aeroplane when combined with an air duct leak, air conditioning system contamination or, if installed, malfunction of the fire extinguishing system in the Class 'C' cargo compartment.
* * * * * The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.