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Sikorsky S-92: From Design to Operations

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Sikorsky S-92: From Design to Operations

Old 21st Mar 2009, 09:09
  #1321 (permalink)  
 
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Only one that involved significant oil loss - as DCVC mentions earlier - and that was the one that precipitated the ASB in question. Other events have resulted in land immediately guidance from the RFM due to smoke, or reduced pump output pressure, but in fact the integrity of the gearbox was not compromised to the degree that failure would result. It's all in the preceeding pages
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Old 21st Mar 2009, 10:07
  #1322 (permalink)  
 
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Thanks for the information and past history Deux and 212. Have corrected my error, pity I can’t edit the quote. The constructive discussion technical detail and background information being available as developments move forward, the openness and genuine feeling to pass on information to all demonstrates what PPRuNe is all about. Thanks to all.
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Old 21st Mar 2009, 11:28
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212Man,

Whilst I am encouraged by the fact that only one incident has actually resulted in total loss of GearBox lubrication, surely we should be similarly concerned with the number of pressure losses, that would have resulted in 'Land Immediately' guidance from the RFM ?? Especially with so many 92's operating offshore, and with few pilots now willing to test the dry running capability beyond the time it takes to descend from 3,000 ft to the Sea.
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Old 21st Mar 2009, 12:26
  #1324 (permalink)  
 
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Pump failure

There was a short period when OEM supplied technical information was interpreted that, like the S-70, a single pump failure would allow a pressure as mentioned in your obsolete reference. It was later learned after a North Sea operator experienced a pump failure that the pressure would indeed be "as low as" 5 psi. There is no missing psi as it never existed. The information was corrected in revision 1.4 and the latest revision to that document is 1.7.
It is also curious that the filter bowl studs were identified for replacement some time ago after an incident with the Australian operator of S-92's where a significant amount of MGB oil was lost thru a compromised filter assembly. None of this is secret. The MGB does continue to appear be an achillies heel of this otherwise incredible aircraft.
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Old 21st Mar 2009, 12:33
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"FAA May Ground Sikorsky Helicopters" (WSJ article)

See link below to WSJ article:

FAA May Ground Sikorsky Helicopters - WSJ.com

A post from a related Rotorheads thread:

The Transportation Safety Board of Canada said the Federal Aviation Administration in the United States will issue an emergency airworthiness directive stipulating that all operators of the Sikorsky S-92A helicopter must install improved steel mounting studs, replacing titanium studs, before the choppers fly again.
But a spokeswoman for the FAA said Friday it was still reviewing what the TSB found.
“We are considering an action to take, but we certainly haven’t issued anything yet and I don’t think we’ve determined when and exactly what we’re going to issue yet,” Laura Brown said from Washington, D.C.
“It’s just a little bit ahead of where we are on this ... they (TSB) made it sound like a fait accompli and it’s not yet.”
There seems to be confusion as to whether a grounding has been ordred or not. Can anyone post the official text of such an order?

Last edited by EN48; 21st Mar 2009 at 12:59.
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Old 21st Mar 2009, 14:04
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They are not grounded, but the January ASB has been revised to Revision A, that changes the compliance time from " at the next 1250 hour check or one year" to "before next flight." It also says "compliance is essential."

That's pretty clear guidance, which I think you'll find all operators are following.
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Old 21st Mar 2009, 14:08
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S92's Grounded...

see link...
Coastguard helicopters grounded - Yahoo! News UK
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Old 21st Mar 2009, 14:09
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Not being flown until specific essential maintainance is completed sounds very much like 'grounded' to me - how quickly are the titanium studs going to be replaced worldwide?
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Old 21st Mar 2009, 14:14
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And he stressed: "The aircraft on the South Coast are unaffected."
No but they still don't have a night overwater winching capability yet despite continued promises to sort the lighting and the certification of the SAR autopilot modes.
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Old 21st Mar 2009, 14:15
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Crab, the aircraft are not "grounded" as the certifying authority i.e. FAA, have not made the ASB mandatory by issueing an AD.

Quite why the FAA have chosen to drag their heels is a mystery.

However the operators will no doubt take a sensible attitude when it comes to compliance. A voluntary grounding?

As to your question about timescale. I am sure it varies from location to location. Perhaps some aircraft have already been modified? Over here in the tropics, we should have the final pieces of the jigsaw on site by Monday. Flying Tuesday - maybe?
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Old 21st Mar 2009, 14:22
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It would fair to assume therefore that any aircraft that has had a 1250 since the ASB was issued would have steel studs. So I guess those aircraft will still be flying?
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Old 21st Mar 2009, 14:28
  #1332 (permalink)  
 
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Don't think so. Certainly not the case here!
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Old 21st Mar 2009, 14:41
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Did making certain "assumptions" lead to this latest tragedy?

Forget assumptions here folks....leave them on the ground until the steel studs are installed, checked, and cleared for flight.

I would also take the down time to go over the aircraft from the top of the head cover to the tip of the rotor blades looking for any thing less than perfect. By that I mean....inspect in excess of "Standard" procedure.

Dare we "assume" the titanium stud defect was one of the links to this latest accident or just something that was found coincidentally?
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Old 21st Mar 2009, 14:44
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How can you say the aircraft is not grounded ? If the aircraft is not allowed to fly until the studs are changed then it's grounded, and if Sikorsky have issued the Info to replace the studs before next flight then it isn't volountry either.

NST
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Old 21st Mar 2009, 14:51
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Dare we "assume" the titanium stud defect was one of the links to this latest accident or just something that was found coincidentally?
Seems likely it was a significant link in the chain - the other links probably being that the aircraft should never have received certification against FAR29 in the first place, and the flawed information circulating about crew actions in the event of gearbox oil pressure loss.

Action can be taken to address the first and last of these, not sure about the middle one.

HC
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Old 21st Mar 2009, 14:52
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NST, the difference is that Sikorsky are RECOMMENDING that the modification be carried out before next flight through the issue of an ASB. This does not stop any operator from ignoring the recommendation and flying an unmodified aircraft.

A "grounding" will only come about once the FAA issue an AD, which if they say "before next flight" will ground any S92 until compliance with the AD is complete. Alternatively an individual regulator can issue their own AD (something that is pretty rare, but does happen!) which would ground any S92 registered in the country of that regulator.

This may sound pedantic, but hopefully explains why the S92s are not (technically) grounded?

Last edited by Variable Load; 21st Mar 2009 at 15:18.
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Old 21st Mar 2009, 15:20
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"flawed information circulating about crew actions in the event of gearbox oil pressure loss."

Picking up from something HC said above ......... This theory of 30 minutes dry running time does seem to be a popular myth amongst pilots, not just on the 92 - Perhaps a hang over from its 'beaten to death' supposed BlackHawk pedigree. Could that have been a factor in the crews trying to nurse it back to land, and just how commonly accepted (if at all) was that idea. It certainly seems as if Sikorski marketing was partly to blame for that viewpoint, at least in the early days of S-92 development.
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Old 21st Mar 2009, 15:21
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Dare we "assume" the titanium stud defect was one of the links to this latest accident or just something that was found coincidentally?
Sas, are you actually reading this thread?

How can you say the aircraft is not grounded ? If the aircraft is not allowed to fly until the studs are changed then it's grounded
Because it hasn't been grounded by an airworthiness approval agency.

The aircraft is allowed to fly.

To do so would be extremely imprudent.

If people wish to bandy Colloquisms around, fine, but expect facts in reply.
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Old 21st Mar 2009, 15:30
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Special

I was thinking more along the lines of Sikorsky's SSA-S92-08-006 referred to in post #1305. I haven't seen the circular but I wonder if it contained poor advice that might have been a factor. Anyone know what it said?

HC
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Old 21st Mar 2009, 15:40
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HC

I was thinking more along the lines of Sikorsky's SSA-S92-08-006 referred to in post #1305. I haven't seen the circular but I wonder if it contained poor advice that might have been a factor. Anyone know what it said?
The circular was simply referring to a possible change in the RFM procedures. It is odd that the regulators have taken such a visible objection to it's content as it didn't actually state anything of substance. It was basically saying " please keep an eye out for an RFM change".

The changes that it was referring to would also not have made any difference to the outcome of this accident IMHO. The drill for an indicated MGB oil px of below 5 psi would still have been LAND IMMEDIATELY.

VL
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