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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 15th May 2009, 18:16
  #401 (permalink)  
 
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Newfoundland company orders S-92 pilots to remain below 7,000 feet

globeandmail.com: Newfoundland company orders S-92 pilots to remain below 7,000 feet

Regards
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Old 16th May 2009, 10:29
  #402 (permalink)  
 
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Not sure what the above complaints are about. That looks like a fairly well researched and balanced article. Maybe over-stressed the Norsk incident a bit, but generally was fair and accurate.

Sikorski's claim that they "take exception to the characterization that the helicopter failed to meet any FAR 29 requirement" just continues to annoy me.

We have the same debate going on here in the UK at the moment - Whilst it may have fallen within the rules, was it within the 'Spirit of the Rules' ??
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Old 16th May 2009, 14:15
  #403 (permalink)  
 
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It's my understanding that the reason behind the main gear oil bypass system was because the transmission could not run 30 minutes with no oil. It was thought that any loss of oil would occur in the external oil cooling system, so if you stop oil from being pumped to the cooler and trap it inside the case you have your 30 minutes. Apparently the transmission was run with a small amount of oil for a long time, enough to satisfy both the FAA and CAA, but with the caveat that below 5psi you land immdiately.

The tragedy of the irony on this forum is the spirited debate between the 225 and 92 groups and that both types suffered catastrophic transmission failures. Aviation always learns from its mistakes, often at a terrible price, so, hopefully, positive things will happen in these cases.
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Old 16th May 2009, 15:43
  #404 (permalink)  
 
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Just to correct the above ..........

The aircraft that crashed with a catastrophic gear box failure was in fact a 332L2, and not a 225.

The cause of this crash has still not been determined and whilst it is fair to say that both types have a similar gear box, they are not the same. The 225 has a basically identical layout to the L2 but has been 'beefed up' for want of a better phrase.

And with regard to the certification of the S92, I refer to previous responses within this thread that questioned, How do you qualify 'Remote Possibility' on a brand new aircraft type ??
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Old 19th May 2009, 22:08
  #405 (permalink)  
 
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Correct me if I'm wrong as I've not been following these threads for a while, but the Globe & Mail article implies 4 MGB oil loss cases. I only recall 3, Broome Australia and Cougar 491 were due to filter housing titanium stud failures, and the Shell Brunei was an over-filled MGB lube oil reservoir causing seal failure.

The Norsk incident was MGB oil pressure drop due to vespel spline failure. I don't recall lube oil leaking in that case.

I still don't agree with the S92 FAR29 compliance, but I'm sure the manufacturer's lawyers will win their case regardless.
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Old 18th Jun 2009, 12:10
  #406 (permalink)  
 
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Interim Report due to be released today by Canadian Authorities.

Lawsuit filed against Sikorsky by families of the passengers aboard the Cougar Aircraft.

http://www.cbc.ca/news/pdf/nl-helico...uit-200906.pdf

Last edited by SASless; 18th Jun 2009 at 12:20.
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Old 18th Jun 2009, 13:19
  #407 (permalink)  
 
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Maybe I missed it, but I didn't see any mention of the RFM's requirement to "land immediately" if oil pressure falls below 5psi.
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Old 18th Jun 2009, 13:41
  #408 (permalink)  
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The Transportation Safety Board of Canada issues an investigation update into the Sikorsky S-92A helicopter accident (A09A0016)

GATINEAU, QC, June 18 /CNW Telbec/ - The Transportation Safety Board of Canada (TSB) is well into a comprehensive investigation of the accident of a Sikorsky S-92A helicopter, Cougar Helicopters Flight 491, which occurred 30 nautical miles east of St. John's, Newfoundland and Labrador, on March 12, 2009.

A thorough, unbiased investigation is necessary to understand as completely as possible all the contributing factors involved in this accident. To this end, a dedicated team of TSB investigators and several TSB Engineering Laboratory specialists is working towards completing the investigation. A number of other specialists and observers from Cougar Helicopters, Transport Canada, Sikorsky, and the Federal Aviation Administration (FAA), along with the accredited representative of the United States National Transportation Safety Board (NTSB), continue to provide valuable contributions to the TSB investigation.

Work Completed to Date

A significant amount of work has been completed so far, but much remains to be done. Dozens of interviews have been conducted with individuals from various organizations. The latest interviews were conducted in May, including a follow-up interview with the sole survivor. More interviews remain to be conducted in the coming weeks. Hundreds of technical and operational documents, weather reports, air traffic control communications, incident reports, studies, and research papers have been gathered, and the review of this material continues. The TSB has examined the main gearbox (MGB), the tail rotor drive shaft, the flight data recorder (FDR), and cockpit voice recorder (CVR). As reported previously, the FDR stopped recording at approximately 1225:17, (1) while the helicopter was about 800 feet above sea level (asl). The reason the recorder stopped remains under investigation. The TSB Engineering Laboratory, in concert with manufacturer's specialists, has been able to successfully retrieve additional data from the aircraft's Health and Usage Monitoring System (HUMS) and flight control computer (FCC) to be able to piece together most of Cougar Helicopters Flight 491's flight profile below 800 feet. While this portion of the flight profile is still in a preliminary stage, and further analysis is required, the following additional factual information can be released at this time.

Factual Information

Examination of the MGB indicates that there was no loss of main rotor drive and that the main rotor blades were rotating at the time of the impact. The examination of the MGB also revealed that the tail rotor drive gears had been severely damaged, resulting in a loss of drive, causing it to stop producing thrust. Further examination is being carried out by the TSB Engineering Laboratory to determine the cause and sequence of this loss of tail rotor drive.

The metallurgical examination of the titanium oil filter attachment studs revealed fatigue cracking in the studs as well as evidence of thread damage. A detailed metallurgical examination of the studs, nuts, and filter bowl is under way to identify the origin of the fatigue cracks and to determine the fracture mechanism.

Just before the recorder stopped, engine power was reduced, a descent from 800 feet was initiated, and the speed of Flight 491 began to decrease from 133 knots. The helicopter continued to descend and to slow down in a controlled manner, until about 1225:44, at which time driving power to the tail rotor was lost. At this time, Flight 491 was heading 290 degrees magnetic (M) at 85 knots and was descending through approximately 500 feet. At 1225:47, a shut-down of both engines was initiated, which is consistent with a tail rotor drive failure emergency.

Subsequently, the aircraft experienced a number of large and rapid attitude changes. At 1225:54, Flight 491's pitch attitude increased from approximately 10 degrees nose down to about 16 degrees nose up, which is consistent with a flare for an engines-off landing. The helicopter struck the water at approximately 1226 in a slight right-banked, nose-high attitude at an approximate location of 47 degrees 26'03" N, 051 degrees 56'34.8" W, with moderate speed and a high rate of descent. The wreckage was found at a depth of 165 metres on a bearing of 283 degrees from the surface position.

The Sikorsky S-92A flotation system activation switch was found in the armed position after recovery. The helicopter experienced significant forces during the impact with the water, and examination of the inflation bottles indicates that they had not released their compressed gas to inflate the flotation collars. The reason the collars failed to inflate is still under investigation.

Investigation Activities in Progress

Continued investigation activities being finalized include evaluations of the Flight 491 flight profile in an S-92A simulator. Investigators from the TSB and other agency specialists will recreate as closely as possible the accident flight profile to add to the understanding of the challenges encountered by the pilots of Flight 491. In addition, pilot training, human performance aspects, crew resource management, and cockpit ergonomics will be evaluated.

Oil filter bowl studs on all Sikorsky S-92A aircraft have been replaced with new steel studs in accordance with a Sikorsky Aircraft Alert Service Bulletin (ASB). Compliance with the Sikorsky Aircraft ASB was subsequently mandated by an FAA Airworthiness Directive (AD).
The investigation has revealed that, even though the Sikorsky S-92A MGB was certificated to meet requirements of Part 29 of the Federal Aviation Regulations (FAR 29) of the United States FAA, there is a perception in some areas of the aviation community that the MGB can be run in a dry state-that is, without lubricating oil-for 30 minutes. FAR 29 does not require run-dry operation of a gearbox to meet the 30-minute "continued safe operation." Based on the applicable guidance material at the time of certification, the lubrication failure modes of interest were limited to the failure of external lines, fittings, valves, and coolers. This practice was consistent with industry experience, which had found that loss of lubrication tended to be associated with external devices. Therefore, the possibility of a failure at the oil filter was considered to be extremely remote. As a result of the fracture of the filter bowl mounting studs, resulting in the loss of a large quantity of oil, the certification guidance material is being reviewed. Additionally, the FAA and Sikorsky Aircraft are working to identify all the modes of failure that might lead to Sikorsky S-92A MGB oil loss, determining their probability of occurrence, and developing appropriate mitigation strategies.

The Sikorsky S-92A Rotorcraft Flight Manual (RFM) has been reviewed regarding MGB oil pressure loss below 5 pounds per square inch (psi) and the need for pilots to land immediately. An RFM revision has been approved by the FAA and Transport Canada.

A number of issues regarding survivability such as passenger immersion suit and crew flight suit effectiveness, use of underwater breathing devices, adequacy of survival training, adequacy of general ditching procedures, personal locator beacons, weather/sea state flight limitations, and Sikorsky S-92A flotation system are currently under investigation.

Safety Action

As the TSB investigation progresses, the team continues to work closely with the other agencies involved. Safety concerns have been communicated directly to these change agents and have resulted in safety action taken by Cougar Helicopters, Sikorsky Aircraft, and the various regulatory bodies.

Cooperation with Other Agencies

The TSB is working in cooperation with other external agencies such as the Canada-Newfoundland and Labrador Offshore Petroleum Board (C-NLOPB) to ensure that the upcoming public inquiry by retired Justice Robert Wells does not impinge upon the work being done by the TSB under our mandate.

To this end, several exchanges of information have occurred and meetings have been held to coordinate activities. The general concerns of offshore workers have been passed to the TSB and those concerns appropriate to the TSB's mandate have been checked against the investigation issues already under consideration by the investigation team. The other concerns of offshore workers have been addressed by an external Helicopter Operations Task Force, a working group composed of representatives from the helicopter operator and the oil companies.

As always, the thoughts of the TSB investigation team go out first to the families who lost loved ones on board Flight 491. The investigation work of the TSB team on this accident will help all understand what happened in this accident and hopefully prevent any similar accidents from happening again in the future.

The TSB is an independent agency that investigates marine, pipeline,railway and aviation transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.

The investigation update and photos are available on the TSB website at
www.bst-tsb.gc.ca.

----------------------------
(1) All times are Coordinated Universal Time (UTC).
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Old 18th Jun 2009, 13:49
  #409 (permalink)  
 
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They gloss over the fact the FAA and other such agencies certified the aircraft as well.

You can say anything you want in a filing....proving it in court is an entirely different matter. Typical lawyer prays there will be an out of court settlement so he can claim his prize money for not much work and zero risk.
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Old 18th Jun 2009, 14:55
  #410 (permalink)  
 
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Here is the latest from the TSB site:

Transportation Safety Board of Canada - Featured Investigations - Aviation - 2009 - A09A0016

carholme
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Old 18th Jun 2009, 17:34
  #411 (permalink)  
 
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Key Point?

Examination of the MGB indicates that there was no loss of main rotor drive and that the main rotor blades were rotating at the time of the impact. The examination of the MGB also revealed that the tail rotor drive gears had been severely damaged, resulting in a loss of drive, causing it to stop producing thrust. Further examination is being carried out by the TSB Engineering Laboratory to determine the cause and sequence of this loss of tail rotor drive.
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Old 18th Jun 2009, 17:49
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As it goes on to say that "the aircraft entered the water at a high rate of descent" makes you wonder just how much rotor RPM existed.
Previous TSB reports state that it impacted with 20g.

Another important question which comes to light after verifying that the floats were "armed" is why they failed to deploy?

carholme
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Old 18th Jun 2009, 20:08
  #413 (permalink)  
 
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I'm assuming that the tail rotor drive pinion is normally lubricated by the MGB lube oil system. Is this a known weak point in this type of MGB design?

As for the flotation collars not working, I'm assuming that the rate of descent and high G forces may have played a part there. The fact that the pilots were attempting an auto-rotation due to tail rotor failure and got their speed below 85 knots to arm the flotation system just re-enforces that they were doing their best with what they could and by the book.

What's still bugging me is why were they flying at 800 feet and 133 knots when they knew that the MGB lube oil system was compromised? What height would you have to be at to ensure that an auto-rotation operation could be implemented effectively? Was the lube oil temperature reading falsely low, and until the tail rotor drive failed they had no knowledge of anything else amiss that would warrant going from land as soon as possible to land immediately? Has the RFM been fully updated to ensure that this cannot happen again?

Going forward, would it not make sense to have temperature sensors at all critical points in the MGB? These could then pick up excessive heat build-up and force a land immediately action as well as lube oil pressure < 5psi. The only other options are to have either an ELS and/or more robust MGB components to achieve a true dry-run capability. I wonder what the CH-148 new MGB design is going to be...

Last edited by maxwelg2; 18th Jun 2009 at 21:37.
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Old 18th Jun 2009, 20:36
  #414 (permalink)  
 
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So sad , sounds like if the TR drive had not failed at the critical moment they may have had a fighting chance. One thing I am not clear on , though it probably would not have made any difference if you are sure you are ditching would you not deploy the floats once you have reduced speed rather than just arming. Or is the SOP just to arm and allow the auto inflate to happen after you have hit the water surface ?. Does any one have the ditching procedure from the Flight Manual they could post .
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Old 18th Jun 2009, 21:54
  #415 (permalink)  
 
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Or is the SOP just to arm and allow the auto inflate to happen after you have hit the water surface ?. Does any one have the ditching procedure from the Flight Manual they could post .
The RFM states that the floats are not designed to absorb the force of water impact and must only be deployed after water entry. Therefore SOP's are not to deploy the floats before hitting the water. They are armed and then the immersion switch should deal with the inflation.
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Old 18th Jun 2009, 22:11
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Curiouser and curiouser, which came first, loss of oil from the MGB or damage to the T/R Drive? I would have thought that when the MGB lost it's oil the epicyclic gearing would have failed first because of the torque loading, but perhaps the T/R Drive gearing failed because metal particles dropping from the epicyclic contaminated the T/R Drive enough to break up the gears.
A major concern is the reported failure of the flotation system.
It is also understood that the flotation beacons did not operate, in my old company the beacons were wrapped in the liferafts so if the liferafts were not manually deployed no beacons. Automatic deployment of the beacons without the liferafts should be considered, this may also be relevant in the case of Air France 447.
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Old 19th Jun 2009, 14:16
  #417 (permalink)  
 
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CEFOSKEY - A tail rotor drive failure from <800' would be quite difficult to deal with even when already pretty much in autorotation, though the report just says descending, not autorotating. With significant power on, the intial yaw would likely cause a serious upset. Looking at the pictures of the tail drive here,





if the tail drive pinion was in such a bad state, think what the rest of the gearbox would be looking like. You state "the torque should have been almost zero", this may be true (though probably not at the time of failure) but you are assuming no increased drag from a seriously damaged main transmission. In reality once engine power was removed there would likely be significant negative torque causing the fueslage to rotate anti-clockwise. The S92 is bus-shaped at the best of times, I don't think it has much weathercocking effect without a tail rotor going round. Most likely it spun, if not immediately, then as the speed was reduced in the flare.


HC

Last edited by HeliComparator; 19th Jun 2009 at 15:09.
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Old 19th Jun 2009, 14:40
  #418 (permalink)  
 
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HC,

Bit snippy that....after all he was asking a question seeking some enlightenment. Put a bit of sweetner in that castor oil !
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Old 19th Jun 2009, 14:58
  #419 (permalink)  
 
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CFEOSKEY - if it truely was an open question, not a rhetorical question, then I apologise. It was the addition of the second sentence that caused my interpretation that you were really saying "so what was the problem, surely its easy enough to autorotate with no tail rotor especially when the torque was near zero". This is the problem with the written word, it can be interpreted in different ways. Only you will know what the thinking behind your question really was...

In the mean time, I have deleted the first sentence & last para.

HC

Last edited by HeliComparator; 19th Jun 2009 at 15:09.
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Old 19th Jun 2009, 15:16
  #420 (permalink)  
 
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HC,

As there are no photos or discussion of the tear down inspection of the MGB beyond the mention of the Tail Rotor Drive failure and the photos that pertain to that.....we can make no assumptions of what the rest of the gearbox looked like. One would be flat assed guessing what it looks like.
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