Laboratory investigations of the returned parts have highlighted some galling marks at the interface
between the mating surface of the hose elbow and the QRC, which may be attributed to the effects of
vibration.
While this investigation was proceeding, it was noted some cases of hydraulic leakage were
coinciding with piston housing loose on MLG brakes in service. Quality investigation identified a batch
of potential defective bolts which are suspected to be the root cause of the piston housing loose
issue, that could generate vibration of the brake unit. These bolts have been delivered on new brake
units and as spare parts. Quality issue has been corrected and the MLG brake unit fitted at delivery
since MSN 5800 have compliant bolts.
More information on this issue is provided in document Ref. 1 and Ref. 4.