AD NUMBER: 2009-24-09

MANUFACTURER:  Airbus Model A330-200 and -300 Series Airplanes; and Model A340-200 and -300 Series Airplanes
SUBJECT: Airworthiness Directive 2009-24-09

SUMMARY:This 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:

An A330 operator experienced a low level of the Yellow hydraulic circuit due to a loose[ning] of check valve part number (P/N) CAR401. During the inspection on the other two hydraulic systems, the other three CAR401 check valves were also found to be loose with their lock wire broken in two instances.
A340 aeroplanes are also equipped with the same high pressure manifold check valves.
Investigations are on-going to determine the root cause of this event. Additional cases of CAR401 check valve loosening have been experienced in service on aeroplanes having accumulated more than 1000 flight cycles (FC). The check valve fitted on the Yellow hydraulic system is more affected, probably due to additional system cycles induced by cargo door operation. The loss of torque due to pressure cycles could contribute to check valve loosening, resulting in a leak and finally the loss of the associated hydraulic system and, in the worst case, of the three hydraulic systems of the airplane.

FMI: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/94E5384A63470AF08625767B00593A98?OpenDocument