MilEME09 said:
The S92 crash off NFLD a few years ago was the result of an oil leak from the gear box.
That's a massive oversimplification. I suggest you read
https://www.tsb.gc.ca/eng/rapports-reports/aviation/2009/a09a0016/a09a0016.html In particular though, I draw your attention to:
7.The S-92A rotorcraft flight manual (RFM) MGB oil system failure procedure was ambiguous and lacked clearly defined symptoms of either a massive loss of MGB oil or a single MGB oil pump failure. This ambiguity contributed to the flight crew's misdiagnosis that a faulty oil pump or sensor was the source of the problem.
8.The pilots misdiagnosed the emergency due to a lack of understanding of the MGB oil system and an over-reliance on prevalent expectations that a loss of oil would result in an increase in oil temperature. This led the pilots to incorrectly rely on MGB oil temperature as a secondary indication of an impending MGB failure.
9.By the time that the crew of CHI91 had established that MGB oil pressure of less than 5 psi warranted a "land immediately" condition, the captain had dismissed ditching in the absence of other compelling indications such as unusual noises or vibrations.
MilEME09 said:
DND originally required a 30 minute run dry gear box for safety reasons. However with delivery very behind schedule and the gear boxes not yet made the choice was made to axe that modification.
Another massive oversimplification. Although the press reports of the time only hint at it, it is subject to the certification and airworthiness requirements of the aircraft. In this case, the aircraft is certified to FAR-29. I draw your attention to other quotes from the same flight safety investigation:
The FAA's Notice of Proposed Rule Making (NPRM) was published on 27 November 1984. For section 29.927(c)(1) Category A rotorcraft the NPRM stated:
It must be shown by tests that each rotor drive system, where the probable failure of any element could result in the loss of lubricant, is capable of continued operation, although not necessarily without damage, for a period of at least 30 minutes at a torque and rotational speed prescribed by the applicant for continued flight, after indication to the flightcrew of the loss of lubricant.
The FAA's Final Rule was published on 02 September 1988. The Final Rule took into account comments received from stakeholders. One commenter had noted that, as proposed, the requirement in paragraph 29.927(c) could be interpreted to preclude credit for auxiliary lubrication systems or to require consideration of lubricant failures to self-lubricated bearings. The FAA stated that this was not intended, and the wording of paragraph (c)(l) was revised to eliminate this possible ambiguity. The proposed rule was therefore modified to require that:
Unless such failures are extremely remote, it must be shown by test that any failure which results in loss of lubricant in any normal use lubrication system will not prevent continued safe operation, although not necessarily without damage, at a torque and rotational speed prescribed by the applicant for continued flight, for at least 30 minutes after perception by the flight crew of the lubrication system failure or loss of lubricant. (emphasis added)
The update of the design requirements for large, multiengine transport rotorcraft (Category A) recognized the need for main gearboxes (MGB) to have a significant capacity to operate following a loss of lubricant in order to optimize eventual landing opportunities. This consideration led directly to the introduction of the 30 minute requirement to operate after a loss of MGB lubricant. However the introduction of the "extremely remote" concept following the comment phase of the rule-making made it possible for a helicopter to be certified without being capable of operating for 30 minutes with only residual lubricant. Category A rotorcraft certified under the "extremely remote" criteria may not be capable of continued operation for 30 minutes with only residual lubrication. These helicopters remain vulnerable to gearbox failures stemming from unforeseen massive losses of MGB lubricant, placing passengers and crew at risk.
Therefore, the Board recommends that:
The Federal Aviation Administration, Transport Canada and the European Aviation Safety Agency remove the "extremely remote" provision from the rule requiring 30 minutes of safe operation following the loss of main gearbox lubricant for all newly constructed Category A transport helicopters and, after a phase-in period, for all existing ones.
Ie, there is an ongoing problem with what "run dry" means, and the FAA rule in FAR 29 allows exceptions. Given the Cyclone is certified under FAR-29 led to issues. Basically it is about it is 30 minutes
after indications to the crew, unless the cause is extremely remote, as shearing of the three titanium studs was supposed to be, and still is considered that way as the three studs have been replaced by 6 steel ones.
However, to be clear (and I checked the checklist), if there are indications of an
imminent gear box failure, the S-92 then, and now, and the Cyclone now, must
Land Immediately. The S-92 Newfoundland incident crew did not fully understand what the indications were (again, see the report).
MilEME09 said:
I hope to God that wasn't the cause otherwise our procurement system cost us 6 lives.
I also hope that is not the case; however, I'm relatively certain it isn't. The S-92 crash was about the factors that led them to not understand they were facing an imminent MGB failure. Nothing in the Cyclone incident that has been released indicates they had any indication of an MGB failure.
By the way, the S-92 incident pilot was ex 12 Wing and was a good stick as well.
I'll also note, again, that much of this speculation is being fueled by
one ex- Sea King pilot in the media. He first speculated they wouldn't get the CVR/FDR because it was so deep, demonstrating a lack of knowledge how the CVR/FDR is designed to depart the aircraft. Once it became clear that is not the case as it was recovered, he then started speculating that they need the wreckage in any case because the CVR/FDR is not sufficient. There are no indications at this point that is the case; how about we wait until the experts analyze that data, in addition to the eye witness accounts which
have not been released (and no, it's not a coverup). Even it is a MGB Lube problem, which I doubt but have no contrary information either, the FDR well tell us a great deal.
Am I showing my frustration???
