Aux tanks: I personally can't see either the tanks or the sector length having an effect on the filter studs.
Filter removals: This seems a bigger potential factor. Sadly it is not possible from the information presented to determine if the CHC and Cougar filter removals (particularly on the two aircraft that had oil oss in flight) was significantly worse than other operators.
Oil filtering: 212man, yes perhaps some operators choose to pre-filter their oil. However if that was essential it shuld have been in the Maintnance Manual!
Titanium: No matter what reason, gaulling makes titanium a poor material choice and this should have been considered in the FMEA.
Part 29.927(c)(1) Design Assessment FMEAs: As Sikosky failed to even consider the oil loss from the filter housing (see below) it is no surprise thatneither was the material choice challenged or recoconsidered when service experience showed high filter removal rates (and so high gaulling potential)/
Neither the FAA nor Sikorsky specifically considered a failure in the MGB oil filter bowl assembly, or its attaching fasteners, in the context of Part 29.927(c)(1).
Studs are critical: Two events of oil loss now show that the studs are what FAR29 defines as 'Critical Parts', irrespective of what material they are.
AFAIK they are still not subject to the enhanced critical parts control regieme required by FAR29 for such parts.
Social media: My reading of the TSB report is that they are implying that they believe that contributors to a certain forum did understand the situation but TSB aren't necessarily claiming that contributors actually wrote what they understood.
Blackhawks: Great info guys! A contact in Australian Army tells me that their aircraft have steel bolts (not studs) - highlighting another difference. If the US Army documents are correct in saying the its MGB can operate for 30 minutes without oil then the S-92 is a massive retrograde step and by no means the wonder that some made it oput to be.