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Helicopter crash off the coast of Newfoundland - 18 aboard, March 2009

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Helicopter crash off the coast of Newfoundland - 18 aboard, March 2009

Old 14th Nov 2009, 18:19
  #501 (permalink)  
 
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Unless such failures are extremely remote...
Yeah, but again, who gets to determine that? Does the manufacturer have the option of telling the certification authority, "We believe that a failure of the lubrication system of our new transmission will be extremely remote. The case will never crack, and none of the accessories mounted to it, like...ohhhhh...the TRANSMISSION OIL FILTER, which is under considerable pressure...will never crack and allow oil to leak out!"

Is that how it works?

Because that is apparently how it worked for the S-92.

That "unless such failure are extremely remote" stuff is horrible wording for a regulation.
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Old 14th Nov 2009, 20:36
  #502 (permalink)  
 
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I suppose the problem with regulations is how do you word them to take into account the improbable but obvious. NASA refers to "criticality one" to describe components that, if they fail, the rocket, shuttle etc. will crash.

Anything that flies has, and will always have, lots of items that can be concidered "criticality one." For airplanes, obvously the wings and tails are at the top of the list. For helicopters, blades, masts, gearboxes and even tailbooms are a few such items.

So how does a regulator write language to take into account items like those that are "criticality one?" I would suggest that regulators, like engineers and managers work in a world of compromises. Just as an engineer must design a system that is best possible, by definition he will make compromises, the regulator will write language that will try and make the system the best possible but, in the end will also make compromises.
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Old 14th Nov 2009, 21:43
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Back on my hobby horse for a moment (which one you ask?): Which helicopter would you rather fly, the one that loses all its oil quite regularly but has a genuine 30 mins dry running time, or the one that doesn't have 30 mins dry running time but is well designed and never loses its oil?

Personally I would prefer the latter.

The certification standards are not particularly strong in this area. They are more concerned with having a fallback mode following a failure than having no failures in the first place.

Certfication standards are written by engineers that don't actually have to fly the products, nor really understand flying.

The problem with having certification standards is that a lot of effort goes into compliance with the letter of them, sometimes at the expense of making a good product.

In other words its "paper safety" and the real goal of making a robust and reliable helicopter that does not kill people is lost in the beaurocracy.

Maybe we should have no certification standards but rely on the manufacturers fear of being sued to make a robust product? No certification standards means quicker fixes - as has been repeatedly proven, certification does not guarantee (or even make likely) a product that works properly without design flaws, but by heck it certainly slows down bringing any fixes into place to cure those flaws.

HC
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Old 15th Nov 2009, 08:20
  #504 (permalink)  
 
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30 minute loss-of-lube

The FAR29 MRGB 30 minute requirement is for a loss of lube system functionality condition, and does not necessarily imply that the MRGB is operating entirely without lubricant. And as for the S-92 MRGB being qualified as having a lube system failure event considered "extremely remote", that went out the window with AD 2009-07-53
That single point lube system filter failure should never have gotten past a proper FMEA of the S-92 lube system.

I have designed some rotorcraft MRGB's. And there are several established ways to ensure a 30 minute loss of lube capability in a rotorcraft MRGB. The most common approach is to use high temperature gear (X-53) or bearing (M50NiL) materials for the critical gears/bearings, that can operate at temperatures up to 600degF without losing temper. The other approach is to provide a secondary, "total loss" back-up lube system that provides just enough lubricant flow to keep the friction heat generated by the critical MRGB gears and bearings within their capabilities.

MRGB lube systems are now always designed with the lube oil pipes as integral parts of the housing castings, in order to minimize leaks. And potential oil system leaks are one of the main things that the FAA looks at when certifying a new MRGB design.

Also, personally I would never have used titanium fasteners on a maintenance item, like Sikorsky did on their S-92 MRGB oil filter housing, due to the known inherent nature of titanium fasteners to gall and seize if not installed under perfect conditions.

Regards,
riff_raff
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Old 15th Nov 2009, 09:33
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HC the good news is that there are light, medium and heavy twins that have been sucessfully tested to simulate an uncontained oil loss from anywhere in the oil system AND have no history of leaks either.

There is also a rule called the design assessment, 29-917, that requires the OEM to assess and minimise all geqrbox failures modes that would be catestrophic or require an immediate landing - just like Cougar faced. When Sikorsky fall back on their defence that the RFM says to land immediately they simply show they failed to meet that requirement:-

http://www.pratt-whitney.com/StaticF...Links_0409.pdf


As an additional safety precaution, in the event of total loss of oil
pressure, a “Land Immediately” instruction is directed by the flight
manual and a controlled landing can be executed.
A burning question is:-
What is Sikorsky doing for the S-76D test?
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Old 15th Nov 2009, 14:48
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From Sikorsky:

If an impending failure is suspected, the primary consideration is to land the aircraft before the failure progresses to a gearbox seizure or loss of drive to the main or tail rotor,” the SSA continues. Sikorsky writes that a “single” indication of a MGB problem (pilots receive MGB temperature, pressure and chip detection system readings) dictates that the helicopter should land “as soon as practical”. Multiple indications, Sikorsky notes, “dictate that the helicopter should land as soon as possible,” while an impending transmission failure “would necessitate that the helicopter land immediately.”

Okay, so it puts it back on the pilots. Did they suspect an "impending failure" of the transmission? Obviously not. To us pilots, "land as soon as possible" does not necessarily mean "crash the helicopter if you have to." And even a notice to "land immediately" would be a tough call. If you were over unbroken forest with no clearings, would you put the helicopter down in the trees and intentionally crash? Or would you continue on, hoping for some little hole to stick the thing?

In the case of the Cougar pilots, without reading their minds it is quite obvious that they considered the ocean below them to be an unsuitable area to land...ergo, they assumed that doing so would be tantamount to crashing the helicopter. Why else would they have *not* chosen to land immediately? Instead, they chose the "land as soon as possible" option. And it was the wrong one. By the time they got the indications of impending failure, it was probably too late. (Was it when the tail rotor drive failed? Or did everything come apart at roughly the same time?)

Complicating things is the fact that we have no way of knowing if we've had a completely loss of transmission oil, as there is no gauge attesting to its level. All we have is the pressure and temperature gauges - and the temperature gauge may be unreliable if there is no oil to measure the temperature of.

So what could the Cougar pilots have been thinking - in those nine minutes - as they tried to figure out why they had no transmission pressure? Certainly that particular failure (the fractured filter mounting bolts) had not occurred yet, so it wasn't among the possibilities. If only they had some indication that all of the transmission juice was gone...

But... Again, would they still have landed? Would they have assumed that their transmission about about to fail?

This accident illustrates the uncomfortably tight squeezes between the rocks and those hard places we pilots sometimes find ourselves in.
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Old 15th Nov 2009, 15:17
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A burning question is:-
What is Sikorsky doing for the S-76D test?
Possibly nothing. The D model is not a new helicopter, just a C++ with some improvements. Same 76 Type Cert, so I don't think they have to do as much proving work as if it was a new design. Just like Eurocopter with the EC225, it is on the AS332 Type Cert. Saves a LOT of time and money if you can do it that way.
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Old 16th Nov 2009, 15:40
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The S92 emergency checklist does list a single indication for a "land immediately." When the MGB oil pressure light is illuminated and the pressure is below 5psi it becomes a "land immediately."

As stated above, the choice of landing in the trees or in freezing water is not much of a choice. Helicopters are the perfect tool for rugged, inhospitable environments - therein lies the dilemma.
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Old 16th Nov 2009, 18:02
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Engineering Ethics - No More, No Less

CEFOSKY said:
squibb, here is your cue to laud eurocopter ____. you were waiting for an invitation, no?

I honestly wish I could discuss the design and current work we are doing regarding the 92 MGB, but threads like these constantly reinforce why these things must stay confidential in analysis and development.

I'd hate for to take anything more from this thread and source it as fact in his monthly SAC-bashing columns in the canadian press.... as its par for the course for him thus far.
You don't really get it do you? It is no more about promoting one helicopter above the other than the Challenger and Columbia accident investigations promoted the Soviet/Russian space programme. This is about preventing accidents by not fudging critical tests. Engineering ethics in fact.


17 people are dead and you are more worried what a Canuck jounro has to say? Time to rethink your priorities buddy.

Or would you rather write the Cougar 17 out of the history books under the same cloak of secrecy you want to apply to R&D? Perhaps a little more integrity, openess and humility over the weaknesses in aircraft design and fewer people will lose their lives.

Uncle Squib's top tip on building long term market share and brand reputation:- get the aircraft right [FONT='Verdana','sans-serif']before[/FONT] you start marketing it under a safety banner. Is that too much to ask?


Most OEMs would not want to be known for producing a rotary Ford Pinto (the Pinto fuel tank was [FONT='Verdana','sans-serif']known[/FONT] to be a problem but fixing the problem that was killing people was deemed too expensive).

As comments above show, the Flight Manual is being used as a last ditch attempt to switch the responsibility for product integrity to the crew by forcing them to take actions that themselves are highly dangerous by the very nature of helicopter operations, this is in lieu of providing a capability that other OEMs can deliver without needing to be creative with FAR29.

Engineering ethics.

-----///\\------
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---|||4-|||-----Remembering
---|||9-|||-----Cougar
---|||1-|||-----Flight 491
----\\\-///-----
-----\\///------
------///\------
-----///\\\-----
----///--\\\----
Remembering Cougar Helicopter's flight 491 | Facebook

BTW I'll be keeping an eye out for the name Peter Cheney - I'd not noticed his name before so thanks for your help on that one buddy!
Articles by peter cheney
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Old 17th Nov 2009, 10:22
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Category A cert

Just to clarify,

how can the S92 still be classed (still officially certified) as a Category A rotorcraft (which by definition it must be under JAR29 due to its weight) if the MGB lubrication failure case has now shown to be not 'extremely remote'?


In order to allow it to continue flying I assume that the rectification action (new studs) revalidated the safety case and that the failure is again regarded as extremely remote hence the S92 is again JAR compliant, but without a 30 minute dry run capability.

or have I got the wrong end of the stick?

DM
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Old 17th Nov 2009, 15:25
  #511 (permalink)  
 
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CEFOSKEY, don't you think you are a bit overley defensive? No OEM has made the perfect gearbox, I think the main issue here remains why this gearbox was certified to the highest standard despite it's track record in service after certification. How was it tested if we missed all these possibilities or is it just bad luck? You have to agree that there just seems to be to many loose ends?
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Old 17th Nov 2009, 15:58
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To victor-papa, and all who castigate SAC for a seeming "design failure" of the S-92 transmission:

From SAC's point of view, a civilian aircraft losing *all* of its transmission oil is an extremely remote possibility. I mean, nobody is shooting at the thing, right? SAC will probably trot out a hoard of "expert witnesses" who'll testify to that issue. I can imagine if they got...well...me on the stand!

SIKORSKY DEFENSE ATTORNEY: So, Mr. FH1100 Pilot, how long have you been flying?

ME: Err, well sir I've been prostituting myself...that is, doing it for money for, oh, almost 28 years. But I've been flying airplanes since 1973 and began helicopter training in 1977. So...I dunno...32 years for helicopters?

SAC ATTY: And how many hours do you have now?

ME: Well, something more than 11,000. I don't really keep track anymore, except for the damn insurance companies and their...no offense...lawyers.

SAC ATTY: And in that time, how many complete losses of transmission oil quantity or losses of oil pressure have you had?

ME: Me? Well...umm...almost...ahh...one.

SAC ATTY: One??

ME: Almost! None, actually. Nearly one, but not quite.

SAC ATTY: So, Mr. FH1100 Pilot, would you therefore say that the likelihood of a complete loss of transmission lubrication would be extremely remote?

ME: That's a fair statement. May I go now? I have to pee.

SAC ATTY: NO FURTHER QUESTIONS! The Defense calls SASless to the stand!

Despite the fact that this was a tragic, deadly accident, I made the above a little humourous because this is exactly what WILL happen when it comes to trial. No matter what we assumed...no matter what the advertising brochures implied or hinted or even said outright...if those pilots had just landed...JUST PUT THE DAMN THING DOWN!...*all* of those people would not have died. It's sad, but true, no matter how much we don't like to admit it.

Sikorsky did what it did, and is now undoubtedly doing "something" (TBA) to control the damage to its reputation. But you can't say we haven't already learned some things from this accident... Something about operations over inhospitable terrain. Something about pilots faced with a lose/lose proposition. Something about our regulatory agencies. And something about Sikorsky.
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Old 17th Nov 2009, 17:15
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FH1100 PILOT, pls do not catagorise me. I am not castrating Sikorsky or any other OEM. I just thought that the previous post was a bit defensive. I did state NO OEM manufactured the perfect gearbox(332L2 in the North Sea). I also stated how did it pass the tests-in other words as you allude as well are the tests done relevant by the authorities? After only 22 years, 7000hrs and operating only over hostile terrain either military, offshore, HEMS or survey I am not critisizing Sikorsky as such but participate as it leads to a better understanding of the circumstances we operate under and the risks. As you alluded to in your humorous court scenario, the problem I have is that it SEEMS that your answers would differ greatly to your questions unfortunately dependant on whether you fly and know the S92/S92 crew or not.

Sorry if I have the wrong perception!
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Old 17th Nov 2009, 19:33
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v-p, my answers would not...could not...change. If an attorney asked me those very questions, there is only one way I could answer. In all my years of flying, I've never had a transmission problem of any kind (other than the spurious chip light). Next witness, please!

In fact...I'm trying to think...I only know of *one* guy who's ever had a transmission failure. He was in a Puma near Atlantic City, New Jersey (U.S.) when it happened. The year was 1978. Fortunately for him, he lived. I don't remember the details, but I do remember that it was hair-curlingly scary to hear them.

Category A. Unless such failures are extremely remote, it must be shown by test that...
Maybe the possibility of transmission failure isn't extremely remote, but the number of actual "such failures" does seem to be. And that is what Sikorsky will argue.
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Old 17th Nov 2009, 23:57
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Actually, the S-92A experience has shown that Sikorsky won't argue anything; the strategy appears to be to keep it out of the media by settling quietly with the next of kin.

I can't say I agree with CEFOSKEY. Sikorsky was quite pleased to promote the machine on this very 'rumor' forum when it suited their needs. The in-house cheerleaders should convincingly respond to the skeptics rather down pom-poms and and skulk off muttering about their self-proclaimed status as experts in the industry.

Public criticism following the issues with S-92A is healthy, particularly if it pressures the decision makers in Stratford to deal with the issues properly. Personally, I'd like to see the remaining aircraft upgraded with transmission that includes the 'derived out' safety feature. I'd also like to know if the people who are telling the users that steel stubs on the filter housing are the same ones who previously represented that ti would meet the need.

Excellent thread.
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Old 18th Nov 2009, 01:30
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Next witness, please!
Trouble is FH1100 Pilot every one has, or can have, a different story to tell. Chalk up two for me, and saw the results of another where a gear wheel came out through the side of the case and removed a jack in the process. Some died, but the remarkable thing was the majority survived.

Edited to add just remembered two other gear box failures that ended well in our organization, and those happened to the same pilot.

Last edited by Brian Abraham; 18th Nov 2009 at 03:10.
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Old 18th Nov 2009, 01:34
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A quick thread observation would be that the MGB incident has all those who ride in the S-92 spooked and wanting to be confident in it once more before getting back on this horse.
Military aviators would simply put this type of issue on the long list of other things trying to kill them and get on with it but civilian types haven't the luxury of having bullets and rockets lobbed at them to help them forget about a questionable MGB issue. I don't believe the helo will ever be as reliable as that most perfect engineering design, the single ball bearing but you can bet SAC works the hardest to make it that way..IMHE.
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Old 18th Nov 2009, 03:28
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I think by now we can all understand that the "extremely remote" issue cannot be definitively cleared up either way, as there is no wording regarding context in the regulation,e.g. remote when compared to what, previous occurances?, for all aircraft ?, by manufacturer ?, by type ?, what if it's a radically different design ?,if it does happen once early in service life and is addressed, does the clock get re-wound ? Hopefully regulators will address this issue for future wording. No doubt some lawyers somewhere will make a great deal of money argueing about it, but it's a no win situation either way.

There are some issues with the MRGB - the cracks appearing in the mounting lugs which has the type under a 10 hour inspection schedule does not calm rattled nerves, so the sooner it's resolved the better.

Everybody wants to see confidence back in the machine, none more so than the people who are transported to work in it. It is important to realize that the perception of the ultimate enduser (PAX) is key to getting this back on track, so any questions or concerns they have should be properly addressed in a professional manner, especially by the people whose job it is to address these issues.

Nobody's interested in looking over someone else's shoulder at the OEM - they know their business.

Just fix any outstanding issues, and let people know if there's a new problem and what's being done to address it. No big secret. All machines require maintenance & repairs - offshore workers realize this better than most as their livelyhood depends on doing just that with some of the biggest, most expensive equipment out there.
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Old 18th Nov 2009, 16:22
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madrock/FH100 Pilot,

The term 'extremely remote' is assigned a numerical value in FAR 29 - i.e. 1:10,000,000 to 1:1,000,000,000.

Those who are interested in the discussion in this thread might wish to glance through the regulations; in particular a search for 'extremely remote' (in context) in AC 29-2C will provide a great deal of illumination.

Whilst I have the platform, I would like to comment on HC's assertion that pilots are not involved in the provision of the Certification Codes. In my experience, the FAA Rotorcraft Directorate at Forth Worth always has several practicing pilots (and recently one was the Head). The CAA also had a number of pilots in the Flight Department working on the provision of the Certification Codes - fewer now because of EASA.

I also witnessed the failure of a planetary gear in the S61 at my base in the North Sea; it was landing at the time.

Jim
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Old 18th Nov 2009, 20:14
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JimL :

Extremely remote events are not expected to occur during the total operational life of a random single rotorcraft of a particular type,but may occur a few times during the total operational life of all rotorcraft of a particular type, that are based on a probability on the order of between 10-7 to 10-9.

....it's still fuzzy......what particular type was used in the original calculation ? all Sikorskys ? all Blackhawks ? all CAT A ? ...........?
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