Maybe NickLappos can answer a question for me regarding the design of the S-92 MRGB lube oil filter housing. I'm not a transmission design expert, but one thing I do know is that with a single path system or component that is flight critical (like the lube oil filter housing), it should be designed with fault tolerance in all aspects. That would include the fastening system holding it in place.
Looking at the photo linked below, it would appear that even though proper fault tolerant design practice was followed regarding using multiple fasteners with dual locking features, the spacing and position of the fasteners may have been deficient. With only three widely spaced fasteners holding that filter housing in place, it appears as though the failure of just one fastener, combined with the force created by oil pressure acting against the large surface area of the filter housing, would be more than enough to dislodge the housing. In other words, this housing design does not appear to have the level of fault tolerance that would normally be required of a flight critical component. This type of flange failure is not unknown, and is something that would be checked for in a thorough FMEA.
Do you know if the filter housing was part of a critical items list? And if so, was this failure mode considered in the FMEA?
Thanks in advance for any insight you might be able to provide. And I apologize if this question was answered in an earlier post, but there's just too many to go back through.
http://www.flightglobal.com/assets/g...x?ItemID=29667
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