Helicopter crash off the coast of Newfoundland - 18 aboard, March 2009
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The same could be said of some OEM brochures.
Well no oil equals no MGB and no flying pretty quick! The press have been pretty effective at uncovering some shocking aspects to this accident and the S-92 certification IMHO.
Well no oil equals no MGB and no flying pretty quick! The press have been pretty effective at uncovering some shocking aspects to this accident and the S-92 certification IMHO.
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I note with interest the claim by Cougar that SAC "misrepresented" how long the 92 would fly without MGB oil. Undoubtedly that was marketed while the AC was undergoing testing and development. Does marketing get out ahead of product development? All the time. Look at the Chevy Volt. Touted as an electric car with a small engine to recharge the batteries, it turns out it is not much more than another hybrid car.
Cougar might want to be careful about how it handles its claim. If they are claiming they have been misled, that infers they still believed the original claim. If management still believed the claim did they pass it on to the crews in training? Did the "land immediately" part of the RFM somehow not receive the emphasis it deserved? If the crews went through FSI for their training, then that was never an issue. I received my type rating at FSI two months before the accident and, at no time, was their ever any discussion of the MGB having a 30 minute run dry cabability. It was treated just like a fire that doesn't go out or a TGB indication with kicking in the pedals - get it on the ground.
Cougar might want to be careful about how it handles its claim. If they are claiming they have been misled, that infers they still believed the original claim. If management still believed the claim did they pass it on to the crews in training? Did the "land immediately" part of the RFM somehow not receive the emphasis it deserved? If the crews went through FSI for their training, then that was never an issue. I received my type rating at FSI two months before the accident and, at no time, was their ever any discussion of the MGB having a 30 minute run dry cabability. It was treated just like a fire that doesn't go out or a TGB indication with kicking in the pedals - get it on the ground.
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js0987
My understanding is that the kicking in the pedals in the sim was the indication that you were already too late - the transmission had failed. Did they tell you that?
My understanding is that the kicking in the pedals in the sim was the indication that you were already too late - the transmission had failed. Did they tell you that?
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I have heard from pilots who trained at FSI that FSI included vibration when simulating a MGB pressure loss, which does not seem to be the case the Cougar pilots faced. Could that have been negative learning?
I wonder if the oil cooler bypass valve always 'worked' in the simulator?
JS perhaps Sikorsky would look less callous if they hadn't changed their plan from certifying '30 minutes run dry' to '30 minutes after a leak is detected in the oil cooler and sealed off'.
Remember when Nick Lappos made a great play after certification that they had repeated the 30 minutes test several times (6 times?) back to back? If the crew were thinking of that, perhaps they would choose to press on when they looked over their shoulder at the pax, looked at the sea and calculated the coast was less than 30 minutes away?
How long would it take for an S-92 at its service ceiling (FL20?) be able to decend then line up for a gentle controlled ditching from the time the pressure dropped below 5 psi? And how many minutes away from this would you fly?
I wonder if the oil cooler bypass valve always 'worked' in the simulator?
JS perhaps Sikorsky would look less callous if they hadn't changed their plan from certifying '30 minutes run dry' to '30 minutes after a leak is detected in the oil cooler and sealed off'.
Remember when Nick Lappos made a great play after certification that they had repeated the 30 minutes test several times (6 times?) back to back? If the crew were thinking of that, perhaps they would choose to press on when they looked over their shoulder at the pax, looked at the sea and calculated the coast was less than 30 minutes away?
How long would it take for an S-92 at its service ceiling (FL20?) be able to decend then line up for a gentle controlled ditching from the time the pressure dropped below 5 psi? And how many minutes away from this would you fly?
Nick Lappos Quoote re Tests
Sox 6, could you be mixing up two very different tests?
We never passed any, much less six, 30 minute loss of oil tests. That failure led to the bypass switch design.
Following the bypass switch incorporation, multiple tests were accomplished successfully to more than 30 minutes ( remember, in bypass, the oil cooler is out of the flow loop and thus oil temperature is of interest ). The results of those tests are reflected in the RFM procedures.
I've known Nick a long long time and he has never put out anything untrue.
Thanks,
John Dixson
We never passed any, much less six, 30 minute loss of oil tests. That failure led to the bypass switch design.
Following the bypass switch incorporation, multiple tests were accomplished successfully to more than 30 minutes ( remember, in bypass, the oil cooler is out of the flow loop and thus oil temperature is of interest ). The results of those tests are reflected in the RFM procedures.
I've known Nick a long long time and he has never put out anything untrue.
Thanks,
John Dixson
How long would it take for an S-92 at its service ceiling (FL20?) be able to decend then line up for a gentle controlled ditching from the time the pressure dropped below 5 psi?
But don't forget that if you get on with it and descend in near-autorotation, there is very little power going through the transmission and tail rotor drive, thus much less heating effect and probably considerable "dry running time" - not that I want to put that to the test
Anyway, isn't max altitude without oxygen FL100 in EASA-land? I doubt there are many S92s flying around above FL100.
I've known Nick a long long time and he has never put out anything untrue
HC
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Haven't had the pleasure of having FSI including MGB pedal kicking as an indication that there's nothing else left to do but die.
I recall the pedal bumps as associated with an impending IGB or TGB failure.
So far the bypass has always worked in the sim - next time I'll have the instructor fail that too.
As far as Sikorsky being "callous" - where did that come from? Corporations do and will defend themselves. The fact that they settled quickly with the families speaks otherwise.
As far as Nick Lappos having a spirited debate about the virtues of the 92 vs the 225, what pilot hasn't done the exact same thing about his favorite aircraft. Speaking of which, what's the latest on the 332 transmission that disintegrated? Ironically, the main argument touting the virtues of a 30 minute run dry proved to be useless in that accident.
I hope all the discussions about the virtues of the 92 and 225 on this board did not play a role in the Cougar pilots decision.
As far as flying at 20,000 feet over the ocean, 30 minute run dry would be great. Never saw much point in going above 6000.
I recall the pedal bumps as associated with an impending IGB or TGB failure.
So far the bypass has always worked in the sim - next time I'll have the instructor fail that too.
As far as Sikorsky being "callous" - where did that come from? Corporations do and will defend themselves. The fact that they settled quickly with the families speaks otherwise.
As far as Nick Lappos having a spirited debate about the virtues of the 92 vs the 225, what pilot hasn't done the exact same thing about his favorite aircraft. Speaking of which, what's the latest on the 332 transmission that disintegrated? Ironically, the main argument touting the virtues of a 30 minute run dry proved to be useless in that accident.
I hope all the discussions about the virtues of the 92 and 225 on this board did not play a role in the Cougar pilots decision.
As far as flying at 20,000 feet over the ocean, 30 minute run dry would be great. Never saw much point in going above 6000.
the main argument touting the virtues of a 30 minute run dry proved to be useless in that accident
HC
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js0287
This site was where the S-92's MGB weakness was first aired and that was before the accident.
You might regard the contributions here as a sound prediction of the S-92's first fatal accident. The misleading claims about the tests that were done with the cooler bypass were the contributions that should have been ignored. - just like a number of marketing presentations that hyped the "latest standards" as a competative advantage.
I think Sox6's ceiling comment really highlights that if Sikorsky wasnt to defend themselves with the excuse that the pilots should have ditched as soon as they got the low oil warning, it shold be possible to do that in the certified flight envelope.
HC
Even if Sikorsky had not been so agressive in their market, would you agree that as FAR29 calls for a 30 minutes loss of lube system test, that the industry would have expected that to either have been done with the worst credible failure or at least an Equivalent Safety Finding raised? Instead the compromise made was no revealed by Sikorsky or FAA.
Sikorsky certainly didn't use the Broome event as a trigger to highlight their weakness to pilots. In fact they were busy issuing advisories on reasons not to land immediately after MGB failure indications and even reiterated those after the Cougar accident prompring this from EASA:
EASA Airworthiness Directives Publishing Tool
The whole business of 'Extremely Remote' has been clarified in AC29 to remove the loophole Sikorsky used. While that AC29 came out after S-92 circulation it was drafted, with industry, before the certification....
JohnD
How much better than lying do you think promoting misleading information on a safety issue is while marketing an aircraft?
This site was where the S-92's MGB weakness was first aired and that was before the accident.
You might regard the contributions here as a sound prediction of the S-92's first fatal accident. The misleading claims about the tests that were done with the cooler bypass were the contributions that should have been ignored. - just like a number of marketing presentations that hyped the "latest standards" as a competative advantage.
I think Sox6's ceiling comment really highlights that if Sikorsky wasnt to defend themselves with the excuse that the pilots should have ditched as soon as they got the low oil warning, it shold be possible to do that in the certified flight envelope.
HC
Even if Sikorsky had not been so agressive in their market, would you agree that as FAR29 calls for a 30 minutes loss of lube system test, that the industry would have expected that to either have been done with the worst credible failure or at least an Equivalent Safety Finding raised? Instead the compromise made was no revealed by Sikorsky or FAA.
Sikorsky certainly didn't use the Broome event as a trigger to highlight their weakness to pilots. In fact they were busy issuing advisories on reasons not to land immediately after MGB failure indications and even reiterated those after the Cougar accident prompring this from EASA:
EASA Airworthiness Directives Publishing Tool
The whole business of 'Extremely Remote' has been clarified in AC29 to remove the loophole Sikorsky used. While that AC29 came out after S-92 circulation it was drafted, with industry, before the certification....
JohnD
How much better than lying do you think promoting misleading information on a safety issue is while marketing an aircraft?
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Suibb66
I've been around a pretty long time and have never attended a manufacturers marketing presentation. Frankly I can't think of any of my fellow peter pilots that have. So, forgive me if I still can't quite understand this obsession with how SAC sold the aircraft. Closest thing to a marketing presentation for me would be the ads in magazines.
You are correct about this board airing this particular issue. That is precisely why the RFM procedure made sense.
I've been around a pretty long time and have never attended a manufacturers marketing presentation. Frankly I can't think of any of my fellow peter pilots that have. So, forgive me if I still can't quite understand this obsession with how SAC sold the aircraft. Closest thing to a marketing presentation for me would be the ads in magazines.
You are correct about this board airing this particular issue. That is precisely why the RFM procedure made sense.
Misleading Information
Squibb66:
You seem to be saying that Nick Lappos put out misleading marketing information re the S-92 MGB after we had failed the no oil test in the lab and did the bypass switch design. Can you provide a dated proof of that?
Thanks,
John Dixson
You seem to be saying that Nick Lappos put out misleading marketing information re the S-92 MGB after we had failed the no oil test in the lab and did the bypass switch design. Can you provide a dated proof of that?
Thanks,
John Dixson
js - Sikorsky brought the prototype S92 to a fancy hotel just out of Aberdeen, everyone invited with lots of free food and drink if you listened to the presentation by one Nick Lappos. I recall it was a well attended do with a very believable presentation from NL, and it certainly mentioned 30 mins dry running time.
How about this press release? http://www.pprune.org/rotorheads/229...ml#post2636118
You can argue that it says "loss of oil", not "total loss of oil" but to say that it can fly for 30 mins following " a loss of a little bit of oil" is a pointless claim. I seems to me there was clearly an intent to mislead.
JD - surely the tests you mention must have been done before certification was awarded by FAA?
How about this press release? http://www.pprune.org/rotorheads/229...ml#post2636118
You can argue that it says "loss of oil", not "total loss of oil" but to say that it can fly for 30 mins following " a loss of a little bit of oil" is a pointless claim. I seems to me there was clearly an intent to mislead.
JD - surely the tests you mention must have been done before certification was awarded by FAA?
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HC's link to post 62 on page 4 of this thread (dated 19 Dec 2002, the date the S-92 was certified) is very powerful in demonstrating misleading marketing claims:
This came out immediately after the FAA certification but prior to the JAA one. After the JAA certification this false claim does not seem to have been repeated.
HC that sales visit was the summer of 2003 IIRC, a year before the JAA certification.
In addition to its civil helicopter capabilities, the rotor system and dynamic components are designed to meet the UH-60 BLACK HAWK ballistic tolerance requirements and all gearboxes are capable of running 30 minutes after loss of oil.
HC that sales visit was the summer of 2003 IIRC, a year before the JAA certification.
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A question and answer from the 225 thread #12 31st July 2004:
Please can you confirm whether or not the S92 also has a true 30 minute run dry gearbox as I'm unclear on this? Is immediate pilot action required in the event of a loss of main gearbox pressure? Does the check-list say "Land Immediately"?
NickLappos
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..... the S-92's oil protection system protected the transmission to the FAR/JAR with such aplomb that we shut the test down at 3 hours, not 30 minutes, with the system still running along (but admittedly pretty close to its end). That is 2 1/2 hours longer than required. The pilot must activate the system, but has several seconds to do so after clear indications, and the checklist does not say "land immediately."
NickLappos
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..... the S-92's oil protection system protected the transmission to the FAR/JAR with such aplomb that we shut the test down at 3 hours, not 30 minutes, with the system still running along (but admittedly pretty close to its end). That is 2 1/2 hours longer than required. The pilot must activate the system, but has several seconds to do so after clear indications, and the checklist does not say "land immediately."
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Unfortunately the Cougar 92 was going to have to ditch - 30 minute capability or not. I can't imagine a sales pitch seven years prior or a discussion on an internet message board overriding the RFM. I certainly hope that Cougar doesn't push the point because that implies just that.
js - I guess we won't know if it was a factor until all the details come out. Faced with a life-threatening situation, there can be a tendancy to clutch at straws and listen to what you want to hear. Perhaps there was something in the chat between the crew and the base along the lines of:
"it says land immediately, but looking at the sea state, if we do it may not be survivable. I am sure that Sikorsky demonstrated 30 mins dry running time, the land immediately is just the Flight Manual being cautious. Lets carry on for a while whilst SAR get going etc"
Hopefully that was not what happened, but I don't think we can rule it out yet.
HC
"it says land immediately, but looking at the sea state, if we do it may not be survivable. I am sure that Sikorsky demonstrated 30 mins dry running time, the land immediately is just the Flight Manual being cautious. Lets carry on for a while whilst SAR get going etc"
Hopefully that was not what happened, but I don't think we can rule it out yet.
HC
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Thanks for that folks.
he1iaviator's post confirms the recollection I had that there were claims of 6 x 30 minute cycles (though of course with most of the oil still in the casing and the oil cooler bypassed - a much better scenario than Cougar had).
Helicomparator's post shows that Sikorsky did make those claims after the FAA certification.
On the EC225 thread the S-92 MGB certification was queried by Vertalop in July 2004. Note the very evasive answers:
http://www.pprune.org/rotorheads/191379-ec225.html
On 1 August 2004 this comment was posted, again asking for clarity:
I also draw readers attention to another discussion on MGB certification on page 20 of the Sikorsky S-92: From Design to Operations thread: http://www.pprune.org/rotorheads/163...ml#post1834904
On 9th April 2005 the following comments on the S-92 FM were made after it had again been claimed that an aircraft that lost oil pressure in Norway and made an emergency landing could have flown for 100s of hours:
I think this might be the only public domain reference to the FM instructions Cougar 491 pilots had in front of them 4 years later.
I can't help thinking that openess can be far less damaging to the reputation of companies and individuals than evasion.
he1iaviator's post confirms the recollection I had that there were claims of 6 x 30 minute cycles (though of course with most of the oil still in the casing and the oil cooler bypassed - a much better scenario than Cougar had).
Helicomparator's post shows that Sikorsky did make those claims after the FAA certification.
On the EC225 thread the S-92 MGB certification was queried by Vertalop in July 2004. Note the very evasive answers:
http://www.pprune.org/rotorheads/191379-ec225.html
On 1 August 2004 this comment was posted, again asking for clarity:
Nick, is it not true that the only way the 92 got through the certification process regarding the 30 mins dry running was by using a manually activated valve that cuts off oil connections to outside the gearbox (cooler etc). The flight manual requires activation within 5 seconds, which is rushed in a modern multi-crew environment. Thus the oil remaining in the gearbox is hopefully not lost (assuming the leak isn't from the box itself). So the 92 cannot cope with total loss of gearbox lubricant? Is my take on that correct? Some have said that that appears to be a bit of a cheat on the certification requirements.
It does seem a bit hypocritical to crow about the fact that the 92 meets all the requirements of FAR29 (1999 version, wasn't it?) and that the 225 doesn't (which is true for a few small areas of the aircraft that have grandfather rights) when there is this question mark over how you got through certification (touch of patriotism by the FAA perhaps?).
It does seem a bit hypocritical to crow about the fact that the 92 meets all the requirements of FAR29 (1999 version, wasn't it?) and that the 225 doesn't (which is true for a few small areas of the aircraft that have grandfather rights) when there is this question mark over how you got through certification (touch of patriotism by the FAA perhaps?).
On 9th April 2005 the following comments on the S-92 FM were made after it had again been claimed that an aircraft that lost oil pressure in Norway and made an emergency landing could have flown for 100s of hours:
Make of it what you will but its interesting to note that if the pressure continues to fall after you have activated the magic switch, its a "Land immediately" item. (this is because there is no true dry running time in an S92). As I understand it the Magic Switch (aka MGB Oil Bypass Switch) cuts off the external pipework to the oil cooler etc to contain leaks. Of course its no good having lots of oil left in the sump if both pumps are duff. I am pretty sure that this was the case in the Norsk incident (there were certainly no leaks, so pressure falling to 5 psi is surely double pump failure - double pump partial failure to be exact as there was some residual pressure.)
According to his last post, Nick's idea of Land Immediately is that its OK to fly for 100s of hours.
start quote:
MAIN GEAR BOX OIL SYSTEM FAILURE
Symptom:
MGB OIL PRES or MGB OIL HOT or MGB CHIP or ACC 1 CHIP or ACC 2 CHIP
CAUTION
The main AC generators are cooled by main gearbox oil. Loss of cooling oil may result in mechanical failure of the generators and loss of main electrical power.
Confirming:
Main gearbox oil pressure is less than 35 psi, or
Main gearbox oil temperature is greater than 130 degrees.
Action:
1. Descend to minimum safe altitude.
2. APU - ON
3. APU GEN - ON
4. Land as soon as possible.
If the MGB OIL PRESS warning indicator also illuminates:
1. MGB OIL BYPASS switch - BYPASS
WARNING
BYPASS must be selected within 5 seconds after the warning indicator has illuminated to ensure an adequate quantity of oil remains in the gearbox. DO NOT activate BYPASS if the warning indicator is not illuminated.
2. Land as soon as possible.
If MGB oil pressure continues to decrease or there are loud/unusual noises, unusual vibrations or progressively increasing power required to maintain flight:
3. Land immediately.
end quote
Its a bit difficult to understand exactly what is going on without the diagram that I asked for - never mind I'll try to see if I can get it another way.
In summary, I maintain that they would (should) have ditched had they not been so close to an installation.
According to his last post, Nick's idea of Land Immediately is that its OK to fly for 100s of hours.
start quote:
MAIN GEAR BOX OIL SYSTEM FAILURE
Symptom:
MGB OIL PRES or MGB OIL HOT or MGB CHIP or ACC 1 CHIP or ACC 2 CHIP
CAUTION
The main AC generators are cooled by main gearbox oil. Loss of cooling oil may result in mechanical failure of the generators and loss of main electrical power.
Confirming:
Main gearbox oil pressure is less than 35 psi, or
Main gearbox oil temperature is greater than 130 degrees.
Action:
1. Descend to minimum safe altitude.
2. APU - ON
3. APU GEN - ON
4. Land as soon as possible.
If the MGB OIL PRESS warning indicator also illuminates:
1. MGB OIL BYPASS switch - BYPASS
WARNING
BYPASS must be selected within 5 seconds after the warning indicator has illuminated to ensure an adequate quantity of oil remains in the gearbox. DO NOT activate BYPASS if the warning indicator is not illuminated.
2. Land as soon as possible.
If MGB oil pressure continues to decrease or there are loud/unusual noises, unusual vibrations or progressively increasing power required to maintain flight:
3. Land immediately.
end quote
Its a bit difficult to understand exactly what is going on without the diagram that I asked for - never mind I'll try to see if I can get it another way.
In summary, I maintain that they would (should) have ditched had they not been so close to an installation.
I can't help thinking that openess can be far less damaging to the reputation of companies and individuals than evasion.
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IIRC correctly Cougar 491 was about 30 minutes from the nearest land...
Perhaps the Cougar crew were also mislead by the 3 other low oil pressure but no opil loss events in Norway and Brunei in thinking they would probably make it to shore OK.
But perhaps they did not read the post by helikiwi on the S-92 thread on 4 July 2008 about the one prior total oil loss.http://www.pprune.org/rotorheads/163...ml#post4222516
Also on the S-92 thread just a few days before the Cougar accident Horror box posted this:
http://www.pprune.org/rotorheads/163...ml#post4743808
Bold text added by me.
BTW I notice CEFOSKEY's postive posts on the MGB have gone.
Perhaps the Cougar crew were also mislead by the 3 other low oil pressure but no opil loss events in Norway and Brunei in thinking they would probably make it to shore OK.
But perhaps they did not read the post by helikiwi on the S-92 thread on 4 July 2008 about the one prior total oil loss.http://www.pprune.org/rotorheads/163...ml#post4222516
The story as relayed to me by those involved....
Day before yesterday an S92 was onroute to Broome on a return flight from an offshore rig when a main Txmsm low oil pressure was noted, shortly afterwards remaining oil pressure ceased completely and a fairly rapid decent was carried out. From time of intial low px indication at 6000ft to touchdown was 8 minutes. The oil filter housing which apparently has 3 studs fastening it to the txmsn was hanging on by one which hadn't broken and most of the oil had been pumped out.
During the incident no overtemp indication occurred and a safe landing was carried out next to a homestead in the middle of nowhere 28 miles north of Broome.
Bristow came to the rescue with a trusty old Puma within 60 mins and the guys were taken on to Broome.
At this stage a Sikorsky rep will be onsite tomorrow with a boroscope to assess the viability of flying it the 28 miles back to Broome where the txmsn will most likely be pulled.
Day before yesterday an S92 was onroute to Broome on a return flight from an offshore rig when a main Txmsm low oil pressure was noted, shortly afterwards remaining oil pressure ceased completely and a fairly rapid decent was carried out. From time of intial low px indication at 6000ft to touchdown was 8 minutes. The oil filter housing which apparently has 3 studs fastening it to the txmsn was hanging on by one which hadn't broken and most of the oil had been pumped out.
During the incident no overtemp indication occurred and a safe landing was carried out next to a homestead in the middle of nowhere 28 miles north of Broome.
Bristow came to the rescue with a trusty old Puma within 60 mins and the guys were taken on to Broome.
At this stage a Sikorsky rep will be onsite tomorrow with a boroscope to assess the viability of flying it the 28 miles back to Broome where the txmsn will most likely be pulled.
http://www.pprune.org/rotorheads/163...ml#post4743808
Loss of MGB PRESSURE is your subject here, and there are a number of indications and causes, so maybe not quite as simple as loss of XMSN oil, but once the MGB pressure drops below 35psi the red warning light appears and you get an audio warning. One is to then manually operate the MGB OIL BYPASS switch within 5 secs. This then bypasses the oil from the cooling system, which consists of teflon hoses and a radiator, routing it directly back into the MGB. This system is the "known" weakness and is stated as "vulnerable to leaks" in the OM! The procedure is therefore to "hope" this is where the leak was, bypass it and descend to MSA and hope you get no further indications. Get some further indications and you can assume maybe guess 1 was incorrect so you get another go, but dont take too long about it. These would include a further drop in MGBP, a HYDS failure - as there is a hydraulic module drive gear taken off the input drive shaft - therefore indicating impending drive shaft fail, maybe an AC failure, or any loud and unusual noises or a combo of ACC and/or INPUT CHIPS. If guess one was wrong, then we can give guess 2 a go and maybe see if there is anything indicating with the ACC modules or INPUT modules. An INPUT CHIP at this stage will certainly result in bringing an engine back, but only if it is suspected that the failure is here. By this time I suspect most of us are looking to get down and hopefully onto the solid ground PDQ but a ditching is also on the cards if nothing solid is available. If all this is getting a bit confusing we can also consider the possibility that there is a problem in one of the dual vane pumps. These use one element for pressu's postere feed and one for scavenge feed. It has been suggested that if one element fails, in particular the scavenge, then the oil can be sucked out by the pressure feed! Now i am lost. Unfortunately this also cools the AC gens, so things are going from bad to worse once more. Again, looking for somewhere to land.
All in all the situation is not very good, and there is a good deal of room for confusion. There are one or two on this forum who have some much better first hand experience of this, so can maybe explain it better.
All in all the situation is not very good, and there is a good deal of room for confusion. There are one or two on this forum who have some much better first hand experience of this, so can maybe explain it better.
BTW I notice CEFOSKEY's postive posts on the MGB have gone.
Squib
I am not quite sure why you are re quoting older posts here but the use of a bypass valve manually (S-92) or automatically (AS332 or EC225) to stop oil going to the cooler is logical as the cooler is a likely place for a leak. EC had automatic oil cooler bypass valves 30 years ago. Why Sikorsky could only manage a manual valve has always been a question in my mind.
Anyway, the leak in both cases was from the filter bowl with terrible consequences.
In the case of the S-92 Sikorsky has now re designed the whole filter bowl assembly (a 2 phase re design but phase 1 is in place now) so I would imagine that the company has gone a very long way to making sure that the oil remains in the MGB casing where it should be.
In my opinion, all transport helicopters operating over hostile environments should be mandated to have a supplementary lubrication system so that the realistically impossible goal of run dry should not be necessary. A few liters of mostly redundant oil in a tank would be a worthwhile thing to have.
I am not quite sure why you are re quoting older posts here but the use of a bypass valve manually (S-92) or automatically (AS332 or EC225) to stop oil going to the cooler is logical as the cooler is a likely place for a leak. EC had automatic oil cooler bypass valves 30 years ago. Why Sikorsky could only manage a manual valve has always been a question in my mind.
Anyway, the leak in both cases was from the filter bowl with terrible consequences.
In the case of the S-92 Sikorsky has now re designed the whole filter bowl assembly (a 2 phase re design but phase 1 is in place now) so I would imagine that the company has gone a very long way to making sure that the oil remains in the MGB casing where it should be.
In my opinion, all transport helicopters operating over hostile environments should be mandated to have a supplementary lubrication system so that the realistically impossible goal of run dry should not be necessary. A few liters of mostly redundant oil in a tank would be a worthwhile thing to have.