II, are you implying that the TSB mis-read the Waldron report and/or is there another version of this report, the one I have I got from CBC's 5th estate website a while ago?
Section 4.21 of the report states that two of the studs were mis-labeled, perhaps that is where the confusion exists.
Section 4.3.1 of the report states that the top stub was the one that had previously failed and had the Nyloc nut fitted. This stud was definitely one of the broken ones according to the report.
Section 4.5.1 states that the lower forward stud was the one that didn't fracture.
On 491 the top stud was the only one not to have fractured.
The TSB went to lengths to describe the Broome incident:
In the Australian occurrence the helicopter was not damaged and there were no injuries. The failure initially appeared to have been related to an isolated field repair. Sikorsky advised its customers of these early findings and also suggested that extra attention be given to the filter bowl fasteners.
After an independent engineering firm flagged galling as a possibility on the titanium studs, Sikorsky completed a safety review of the Australian accident and the failed studs. Sikorsky and the FAA came to understand that the source of the problem was in fact galling. Sikorsky, utilizing a risk management process, made an assessment of the Australian occurrence flight, noting that it was able to continue flight for several minutes following the loss of lubricant without causing serious damage to the helicopter. Based on this assessment, Sikorsky developed its safety action, which the FAA accepted. SSA-S-92A-08-007 was communicated on 08 October 2008 to alert operators of the upcoming AMM Revision 13. These mandatory enhanced inspection requirements aimed to ensure damaged studs would be detected and removed.
Believing that the mandatory enhanced maintenance procedures would mitigate risk to acceptable levels, Sikorsky established a compliance time to the Alert Service Bulletin for the replacement of the titanium studs of one year or 1250 flight hours.
As of 05 November 2008 (date of issue of AMM Revision 13), Sikorsky had not received any reports of damaged MGB oil filter bowl attachment studs. Therefore, all of the S-92A helicopters in service at that time (except VH-LOH) would have been equipped with the original MGB oil filter bowl attachment studs. These studs would have had the nuts installed and removed a minimum of 3 times and, in helicopters with similar flight hours as the occurrence helicopter, the nuts would have been installed and removed over 10 times.
The TSB's examination of new S-92A MGB studs and nuts, similar to the type used on the occurrence helicopter, showed that galling damage developed during the first installation of the nut and became progressively worse with repeated installations. The galling was further exacerbated when the nut was reused. AD 2009-07-53 was issued on 23 March 2009, about 5 months after AMM Revision 13. During this 5 month period, every time the MGB oil filter was changed, it was mandatory for operators to carry out the enhanced inspection and to replace any damaged studs.
After AD 2009-07-53 had been issued, Sikorsky requested that operators return the studs they had removed to comply with the AD. As operators were under no obligation to comply with the request, Sikorsky only received a total of 59 studs from various operators. All of these studs, as well as the studs recovered from the occurrence helicopter and the other Cougar helicopters, had different severities of galling, which would be consistent with a difference in the number of times the nut was installed and removed. Based on the S-92A fleet average monthly flying hours, and the average time between MGB oil filter replacements, it is likely that most, if not all, of the 59 studs returned to Sikorsky would have been subject to inspection at least once during that period.
Since the thread galling was detectable using the new procedures, and given that no damage was reported and that there were no reported problems complying with the enhanced inspection procedure, it must be concluded that most S-92A operators, including Cougar Helicopters, did not implement the new maintenance procedure as specified by AMM Revision 13 and, therefore, damaged studs on the filter bowl assembly were not detected or replaced. As these maintenance procedures were mandatory, the low compliance rate can perhaps be attributed to the possibility that operators did not clearly understand the underlying reasons behind the enhanced procedures and the need to detect and replace damaged studs. That is, they did not appreciate that a failed MGB filter bowl assembly mounting stud would cause an uncontrolled total loss of MGB oil that would eventually lead to the failure of the MGB
To me this reads like SAC is pointing the finger at the operators by placing the onus on them via non-implementation of the AMM. Why would SAC not compare the historical Blackhawk steel stud performance to the S92 titanium studs and immediately realize that there was a material issue as part of their risk analysis process?
I still say that SAC is at fault here for being grossly negligent, JMHO.
Safe flying
Max