Re; Clandestino,
"Are you seriously suggesting a) there could be two one-in-a-couple-million FH events occurring simultaneously with contamination or b) actual mechanism of SAP affecting the FMVs is somehow of concern because we need to make them SAP resistant?"
The contamination test (Ref. pg. 212 of report) requires that the system operate with a mix of particles 0 to 1500 micron size. This failure was caused by contaminant 25 micron nominal size, albeit substantially different from the quartz, road dust, etc. of the test.
When the FMUs were taken apart the report does not show which components were actually non functional. Thumb pressure is not adequate to determine if the metering sleeve was really stuck as a much larger force is available to operate it if the metering valve servo control is working.
I ask about the torque motor - servovalves because the report says nothing about their condition. Since with low operating force and small flow passages they are likely to be more sensitive to effect of contamination than the other FMU components.