Sikorsky S-92: From Design to Operations

[Sikorskyfan]

I recall that the Bell 212 called for a stabilization check torque of the MGB filter 5 to 10 hours after it was removed and reinstalled, also it had (has) four studs.

[maxwelg2]

Guys

After just coming in by supply vessel dodging pack ice and icebergs, 24 hours this time but could have been longer if the narrows had stayed blocked, myself and my fellow offshore colleagues are waiting for the conclusive offshore task force investigation results before we decide to resume flying in S-92s. I myself personally still want answers and physical proof that these helos are being maintained to the highest possible standard, with all known or suspected key component mode failures addressed. Can HUMS help identify faults such as MGB stud pending failure, I think not.

Emotions are still sensitive over here, time is a great healer and in our case is directly linked to PAX confidence in helos. The Bond Puma accident last week could not have happened at a worse time, not that any time is good. Here is an aircraft with an excellent safety record, proving to us all that sometimes accidents happen with completely unforeseen circumstances. This IMO does not apply to the MGB stud failure on 491 as this was previously experienced in July 2008.

Some interesting posts wrt. torquing sequence/procedures and other titanium bolts on critical components. Hopefully these issues will have been addressed by all parties and we will have a safer S-92a.

Personally I would still like to see a 30-minute dry-run time, but being realistic I'll settle for a land immediately RFM condition being enforced and more robust preventative maintenance schedule on critical components. I'll also check out my life insurance cover and make sure that flying in helos is covered...

[Ian Corrigible]

An in-depth report on the S-92's gearbox issues, with contributions from Shawn Coyle. Interesting that the Brunei events are not referenced.

Doomed helicopter failed vital safety test, files reveal

I/C

[Jackonicko]

So the S-92 has no run dry capability, and the AW101 does have.

But that's ok, because the chances of needing it were so remote....

How many times has it happened or nearly happened now?

I wonder whether any of those who took such glee in proclaiming the S-92 to be so much 'safer' than the Merlin, and who went to such lengths to bang on and on about how the S-92 met later, more demanding, certification standards will have the grace and humility to apologise?

The noise and hysteria about this supposedly greater safety gave the S-92 a crucial edge at a critical time, and with a more honest assessment, maybe the civil Heliliner would have happened.

There must be many who'd now be happy to see a three-engined, low vibration, quiet roomy and safe helicopter (with demonstrated 30 minute run dry capability) in service offshore.

[SASless]

The news article makes for some interesting reading.

The FAA and JAA accepted Sikorsky's design after they installed an internal isolation valve that isolates all external MGB lubrication components.

If one assumes the oil filter bowl remains uncompromised....the design more than meets the requirement. Who would have thought the oil filter bowl would be a problem?

However, upon the Australian incident....that situation should have had a second review but it sounds as though "local maintenance practices" were held to blame for that incident which would have muted any second thoughts about the studs themselves it would appear.

Now we have the Cougar crash and it opens up a whole different set of issues.

Primarily, how did the 92 come to be thought to have a genuine 30 Minute run dry capability.

Then in particular, how did this affect the decision making process Cougar OPS and the lost crew used in making the fatal decison to continue flying at a normal power setting at 800 feet while tracking towards the nearest point of land?

Since we are second guessing systems and certification approvals.....what happens if the Standby Cooling System on the EC-225 decides to fail at the same time the gear box loses all of its lubrication contents? Does it have a true 30 Minute Run Dry capability?

After all.....it could happen right?

[HeliComparator]

Primarily, how did the 92 come to be thought to have a genuine 30 Minute run dry capability

Answer - due to manufacturer's sales / publicity material such as was posted last month on this thread, such as was put out at various presentations on the machine, and a Program Manager who would do nothing to dispell the myth.

The answer to your last but one point is harder, we will only know if/when transcripts of the radio conversations and CVR are analysed in TC's report.

But we are lining up a fair list of parties to blame: Sikorsky, the FAA, the JAA, EASA, TC, Cougar Ops, Cougar pilots, the oil companies (those with aviation departments who were aware of the Oz incident). As usual with an accident, it could have been stopped if any in the chain above had acted properly.

The 225 has 30 minute running time after all loss of gearbox oil, using the emegency glycol system. I suppose that is not dry running, but if you want to be pedantic about it there is no requirement for dry running, just running after loss of all the oil. If that system doesn't work, you get a red light to tell you to Land Immediately - its brought on if either the glycol pressure or the air pressure used to atomise the glycol, falls.

HC

[RVDT]

In addition to the issues of the MGB - this one gets missed regularly or poorly interpreted -

Chapt 14 CFR's Part 29.607 Fasteners -

(a) Each removable bolt, screw, nut, pin, or other fastener whose loss could jeopardize the safe operation of the rotorcraft must incorporate two separate locking devices. The fastener and its locking devices may not be adversely affected by the environmental conditions associated with the particular installation.
(b) No self-locking nut may be used on any bolt subject to rotation in operation unless a non-friction locking device is used in addition to the self-locking device.

I am not saying that this particular issue is relevant to the accident in question but if you apply the intent to many aircraft and realise that the loss of ONE attachment is enough to bring the aircraft down and yet the fastener is not locked this way and sometimes if at all. Additionally there is no way of telling if it is in fact locked. There are numerous aircraft out there where the intent of this part of the FAR is NOT complied with or may be under an AMC - (Acceptable Means of Compliance) which in some cases is proprietary and is difficult to get verification of.

Take a walk around a few aircraft with this in mind. The assumption so far is that ONE stud on the filter housing failed.

[Matari]

RVDT:

I am not saying that this particular issue is relevant to the accident in question but if you apply the intent to many aircraft and realise that the loss of ONE attachment is enough to bring the aircraft down and yet the fastener is not locked this way and sometimes if at all. Additionally there is no way of telling if it is in fact locked. There are numerous aircraft out there where the intent of this part of the FAR is NOT complied with or may be under an AMC - (Acceptable Means of Compliance) which in some cases is proprietary and is difficult to get verification of.

I'd be interested to know which fasteners you've seen which are not locked per the FAR requirements. If on your preflights you ever spot a non-locked fastener please let your engineers/mechanics know asap.

However, you may be looking at a self-locking nut and just not realize it. For example, a fiber or plastic insert self-locking nut is easy to spot, as is safety wire. However, many MS nuts are self locking through a "crimping" the metal which runs down on the stud or bolt. Once the nut is secured on the bolt/stud, there is no obvious "locking" device to see. But these nuts are indeed self-locking, they just may not look like it.

Someone earlier on this thread talked about how the nuts on the filter housing studs might have been run down finger tight. Not likely...from the photo of the transmission filter earlier on they looked like self-locking MS nuts to me and I can assure you they require a wrench to run them on to a stud or bolt.

[maxwelg2]

Take a walk around a few aircraft with this in mind. The assumption so far is that ONE stud on the filter housing failed.

I believe that it has been stated/inferred that 2 mounting studs had failed on both the CHC Broome and Cougar 491 filter housing failures i.e. both were found with only one mounting stud still retaining the housing in situ albeit with severely compromised sealing.

[RVDT]

Matari,

I'd be interested to know which fasteners you've seen which are not locked per the FAR requirements. If on your preflights you ever spot a non-locked fastener please let your engineers/mechanics know asap.

Let me see,

AS 350 Servo locking of rod end to piston shaft - ONE locking device.

EC135 - SEMA Actuators - ONE locking device. Same item on 155 is lockwired.

EC 130/135 Fenestron Pitch Change spider bolts - ONE locking device.

The issue is these items are required to have TWO locking devices.

Granted we all know that they don't/shouldn't come loose but there have been cases of incorrect (too short and too long) fasteners being used and the locking is ineffective or their is lost travel in the control run. The fasteners which were too long was the manufacturers fault.

These items continue to perform as designed yet are not in compliance with FAR/EASA Part or CS 27/29 as appropriate the wording is the same.

The fasteners you mention only have a single locking device - which does not comply with the TC Rules as written.

[Matari]

RVDT:

Ok, I understand a bit better now what you were referring to.

I'm not familiar with the specific model types you mentioned, but all the servo connections, PC links, T/R push-pull tubes etc. that I've worked on have had a self locking nut (not always easy to spot) and a cotter pin for the required redundancy. I'm just surprised that the models you mentioned apparently don't have the 2 x locking devices.

One other quick point, however:

(a) Each removable (my italics) bolt, screw, nut, pin, or other fastener whose loss could jeopardize the safe operation of the rotorcraft must incorporate two separate locking devices.

Since the transmission studs are not "removable" but fixed into the transmission case, then the fact that the attaching nuts are self-locking type should, I think, comply with the FAR/EASA.

[RVDT]

Since the transmission studs are not "removable" but fixed into the transmission case, then the fact that the attaching nuts are self-locking type should, I think, comply with the FAR/EASA.

This is getting off topic, but the way I see it that would only be ONE locking device of the fastener. The integrity of the studs is covered in another part of the requirements.

[unstable load]

Probably a bit further off topic, but if a stud breaks then half a dozen locking systems in tandem won't help anything.

[megan]

From AVwebBiz Complete Issue
Sikorsky is designing a fix for the military version of its S-92 series to save a $5 billion contract with the Canadian Forces. The Toronto Globe and Mail reported earlier this week that the S-92 was certified without the normal 30-minute "run dry" capability in case of oil loss in the transmission. An S-92 operated by Cougar Helicopters crashed off Newfoundland two weeks ago 12 minutes after the pilot reported a loss of oil pressure in the transmission. The crash killed 17 of 18 people aboard. The oil pressure loss was caused by a broken stud and an emergency AD was issued for replacement of the studs. But the Globe and Mail obtained documents that showed the S-92 was certified by the Joint Aviation Authority in Europe with an exemption for the 30-minute run-dry capability because Sikorsky convinced the JAA that the chance of gearbox oil loss was "extremely remote." The Canadian Forces has told Sikorsky it will cancel its order for 28 of the military versions of the helicopter (MH-92) unless it complies with the 30-minute run-dry rule. Sikorsky told the Globe a fix is in the works for the military version of the helicopter but didn't specify if civilian choppers would be modified.

Sikorsky spokesman Paul Hunter told the Globe the company is designing the modifications but he couldn't elaborate. "We are designing a system to meet the program requirements and will test and enhance it as necessary," Jackson said in an e-mail to the paper. "I can't publicly describe this technology for competitive reasons, but Sikorsky will verify compliance of the [MH-92] to all requirements prior to aircraft delivery to the Canadian Forces," he said.

[CGWRA]

since when is any media, canadian or otherwise, astute

[outhouse]

So what is actually happening just now? we have information that you know who are now working on a fix for the military version of the 92, MH92 as it seemingly is not up to the required contract specifications, would seem someone has posed the questioned “what happens when it has no oil or no oil pressure and How long have I got to get my arse on the deck’’, seems around 5-10 minutes if you are lucky, is not the answer expected.
On the other side of the fence the same you know who company are saying the S92 met all of the required certification standards and had no requirement to have proved that a run dry time was needed. The little bypass valve did the trick and we proved it, pity they did not add one to bypass the rather naff oil filter design. By the way has any one asked what happens if the filter is placed in the housing the wrong way round?
So a question or two
1. Is our favourite you know who company working on a military fix and why? Apart from the obvious one.
2. Is the failing on the S92 also subject to the same urgency to fix?
I suspect the answer to question two is??

[M609]

Tonight Norwegian media reports that a Norsk/Bristow S-92 made a precautionary landing on the Tor rig due to oil leak during a flight from Ekofisk to Sola. (Does not mention which system that was leaking oil)

A/C stuck on helideck pending repairs.

Helikopter måtte nødlande på Tor - Stavanger Aftenblad

[Hilife]

Outhouse

Yesterday’s Globe and Mail ran another article on this accident and details were posted on Rotorheads.

The article contained the following statement from the manufacturer which was also posted on Rotorheads yesterday;

Sikorsky spokesman Paul Jackson said yesterday that the company is still working on a design that would allow the Canadian Forces' militarized version of the same helicopter to cope with a gearbox oil leak.

"We are designing a system to meet the program requirements and will test and enhance it as necessary," Mr. Jackson said in an e-mail.

"I can't publicly describe this technology for competitive reasons, but Sikorsky will verify compliance of the [MH-92] to all requirements prior to aircraft delivery to the Canadian Forces," he said.

The 2004 contract called for the new helicopter to meet the 30-minute run-dry capability.

Now as I read it and if the information in the article is correct, then 'you know who’ has been contracted by the end customer since 2004 to install and certify a system on the MH-92 that can cope with a serious gearbox leak prior to delivery.

As delivery is not now scheduled until late 2010 and the MH-92 is currently flying on an experimental certificate prior to certification by the authorities (I stand to be corrected if wrong on any of these points), then I don’t see how 'you know who’ can be accused of rushing around like headless chickens looking for an emergency fix on this platform.

The statement above clearly suggests that a solution is in-hand, but not yet concluded, as is likely the case on many systems on any experimental platforms, including the MH-92.

So, if the information in the article is correct the answers to your questions are as follows:

1. Yes. Because it was stipulated in the contract some 5-years ago.

2. In spite of not knowing the outcome of any investigation, but knowing what we do in hindsight and also that a solution is underway on a military sister ship, I think you could likely figure this one out for yourself.

Note: If as you suggest not having a 30-minute Run Dry Gearbox is a failing, then I guess most of the platforms operated in the offshore oil industry should be tarred with this brush. Some platform designs have after all been in service for 40-years and more (plenty of time to come up with a fix), so why not include them as well?

[Horror box]

Note: If as you suggest not having a 30-minute Run Dry Gearbox is a failing, then I guess most of the platforms operated in the offshore oil industry should be tarred with this brush. Some platform designs have after all been in service for 40-years and more (plenty of time to come up with a fix), so why not include them as well?

Whilst I agree with your implication, I am not sure I agree with the principle. I would say we should be striving for safety advances all the time, especially in terms of new technology and design. Dry run capability and whether other types have it or not can be argued until the cows come home, but there is no doubt that it is should be a required safety feature when we are operating at times over 1 hr flying time offshore. 10 mins, means enough time to get into the little orange floating thing if we are lucky/get it deployed/find it in the dark/get out of the upside down sinking heli. The weather is very often not that accommodating, especially in the northern climes, where many months flying are predominantly in the dark, and the sea state is almost permanently hard-wired to scary. I for one would appreciate some sort of time to choose my landing site if possible, and at least give myself and my pax the best chance of seeing our families again if/when this happens again. A night ditching in the N.Sea with 50+ knots of wind is not going to see many survivors, especially when we still only have sea-state 5 floats connected. At least give us a fighting chance.

[Ned-Air2Air]

Another S92 Emergency Landing

Heard there was an emergency landing by a 92 in Norway. Anyone have more info.