View Full Version : Bristow emergency landing
https://www.aftenbladet.no/lokalt/i/OQn7BA/nordsj-helikopter-sendte-ut-ndsignal-men-landet-trygt-pa-sola
HeliMannUK
27th Sep 2020, 18:10
https://www.aftenbladet.no/lokalt/i/OQn7BA/nordsj-helikopter-sendte-ut-ndsignal-men-landet-trygt-pa-sola
There doesn't seem to be a date on that story. Can anyone paste in the full story?
Don't have the full story, but digging a bit deeper gives this as date: "datePublished":"2020-09-25T14:05:55Z"
GenuineHoverBug
30th Sep 2020, 06:26
The essence of a brief statement (https://havarikommisjonen.no/Aviation/Investigations/20-836) last night from the NSIA (previously AIBN) is something like this:
On Friday the 25. of September the crew of a S-92A, LN-ONQ on a return flight to Sola from West Elara, got warning that the oil pressure in the MGB had dropped. Later , as the oil temperature started rising, the crew transmitted a MAYDAY call and continued the descent to 200'. They prepared for a ditching if the pressure drop should continue that far. The landing at Sola was uneventful and they were escorted to parking by the emergency services.
The AIBN arrived the same evening and started their investigation. No causes for the event has so far been establised.
helicrazi
30th Sep 2020, 06:57
Anyone have any more info?
Presume they didnt goto MAN COOL so makes sense the temp increased.
rotormatic
30th Sep 2020, 15:47
Anyone have any more info?
Presume they didnt goto MAN COOL so makes sense the temp increased.
https://verticalmag.com/news/norwegian-s-92-suffers-oil-leak-in-serious-aviation-incident/
SansAnhedral
1st Oct 2020, 13:36
Amazingly lucky. Once again reminding that S92A gearbox is a deathtrap...it cannot actually run dry. Recall their Part 29 certification run-dry "extremely remote" clause basis was on the oil leak occurring in the cooler circuit, and the mitigation was to bypass the cooler loop.
If you lose oil from the MGB itself for any other reason (i.e. filter mount like Cougar, or literally any other main case penetration) then you're hosed.
8 minutes.
Seems odd that just losing 4 litres out of the normal 30 litres should cause such a nasty problem?
I suspect the oil leak was a consequence rather than the cause.
Mechanical problem in the input module, leading to lots of heat being generated, leading to oil seals between modules being compromised, as well as heating up the MGB oil.
Only speculation on my part.
That makes sense Apate but raises the question of the design of the input module.
helicrazi
1st Oct 2020, 17:24
Amazingly lucky. Once again reminding that S92A gearbox is a deathtrap...it cannot actually run dry. Recall their Part 29 certification run-dry "extremely remote" clause basis was on the oil leak occurring in the cooler circuit, and the mitigation was to bypass the cooler loop.
If you lose oil from the MGB itself for any other reason (i.e. filter mount like Cougar, or literally any other main case penetration) then you're hosed.
8 minutes.
Death trap? What rubbish. Turned out alright didnt it. They had a caution, not a warning, the OIL OUT is land immediately, they obviously didnt have that and they had sufficient pressure to continue flight to land.
SansAnhedral
1st Oct 2020, 17:58
Death trap? What rubbish. Turned out alright didnt it. They had a caution, not a warning, the OIL OUT is land immediately, they obviously didnt have that and they had sufficient pressure to continue flight to land.
Simply because this particular incident didn't lead to an actual full oil-out condition since they were already on approach (it would only have been a matter of time with the leak as described) doesn't change the issue that the S92A MGB cannot operate without oil for more than approximately 8 minutes.
The fact that it holds Part 29 certification despite this is mind boggling, particularity since there have been enough incidents of leaks from the MGB case to make the "extremely remote" 10^−7 occurrence clause statistical nonsense.
helicrazi
1st Oct 2020, 18:13
Simply because this particular incident didn't lead to an actual full oil-out condition since they were already on approach (it would only have been a matter of time with the leak as described) doesn't change the issue that the S92A MGB cannot operate without oil for more than approximately 8 minutes.
The fact that it holds Part 29 certification despite this is mind boggling, particularity since there have been enough incidents of leaks from the MGB case to make the "extremely remote" 10^−7 occurrence clause statistical nonsense.
Weren't they on their way back? So it could have been losing oil for the previous 2 hours or so... it was hardly a catastrophic event.
The gearbox has a good record.
HeliMannUK
1st Oct 2020, 19:57
Amazingly lucky. Once again reminding that S92A gearbox is a deathtrap...it cannot actually run dry. Recall their Part 29 certification run-dry "extremely remote" clause basis was on the oil leak occurring in the cooler circuit, and the mitigation was to bypass the cooler loop.
If you lose oil from the MGB itself for any other reason (i.e. filter mount like Cougar, or literally any other main case penetration) then you're hosed.
8 minutes.
over a million hours in the sky, not bad for a deathtrap.
SansAnhedral
1st Oct 2020, 20:58
The gearbox has a good record.
What planet do you live on?
over a million hours in the sky, not bad for a deathtrap.
I'm sure that's comforting to the families of the 17 victims of Cougar 91, or the luckier CHC crew the year before.
But its still an order of magnitude below the number of hours required (10^7) without a single loss of MGB case lube incident to verify its certification loophole basis.
If the gearbox is so good, how come a loss of between 10 and 15% of the oil led to such massive overheating of the input module? 214 degrees C!
helicrazi
1st Oct 2020, 21:32
What planet do you live on?
I'm sure that's comforting to the families of the 17 victims of Cougar 91, or the luckier CHC crew the year before.
But its still an order of magnitude below the number of hours required (10^7) without a single loss of MGB case lube incident to verify its certification loophole basis.
The cougar crew unfortunately didnt help that situation and a false understanding led them to continue flying.
helicrazi
1st Oct 2020, 21:34
If the gearbox is so good, how come a loss of between 10 and 15% of the oil led to such massive overheating of the input module? 214 degrees C!
Because a drop in pressure triggers the cooler bypass... they could have chosen to reverse the bypass and cool the oil, they obviously knew where the issue was and it wasnt the cooler.
Because a drop in pressure triggers the cooler bypass... they could have chosen to reverse the bypass and cool the oil, they obviously knew where the issue was and it wasnt the cooler. so if the problem isn't the cooler, why not reverse the bypass? If the leak is in the no 1 input module its going to keep leaking regardless isn't it? Why risk overheating the engine inputs as well?
Not a 92 driver so just keen to understand.
tonkaplonka
2nd Oct 2020, 09:35
so if the problem isn't the cooler, why not reverse the bypass? If the leak is in the no 1 input module its going to keep leaking regardless isn't it? Why risk overheating the engine inputs as well?
Not a 92 driver so just keen to understand.
I think the purpose of the bypass is to save as much oil as possible in the event of a leak. Hot oil is better than no oil. I can’t remember what the capacity of the cooler is, I’m on leave but it takes a fair amount.
helicrazi
2nd Oct 2020, 09:38
so if the problem isn't the cooler, why not reverse the bypass? If the leak is in the no 1 input module its going to keep leaking regardless isn't it? Why risk overheating the engine inputs as well?
Not a 92 driver so just keen to understand.
Probably because the checklist doesn't say to...
We don't actually know their exact indications, what the pressure was and what visual signs they had. Whatever it was, they got everyone home safe, a good day all around.
Whatever it was, they got everyone home safe, a good day all around.:ok: Agreed - MRGB problems over the water are not nice.
Hot_LZ
2nd Oct 2020, 12:03
They didn’t know where the problem originated from. They had indications of reduced pressure and increasing oil temp. They discussed but opted not to Man Cool as they couldn’t be sure the cooler wasn’t leaking.
LZ
bombdoorsopen
2nd Oct 2020, 15:05
Norwegian S-92 suffers oil leak in ‘serious aviation incident’Estimated reading time 3 minutes, 22 seconds.
Norwegian authorities are investigating what they describe as a “serious aviation incident,” after a Sikorsky S-92A suffered an oil leak that forced the crew to declare mayday before landing safely.
The incident took place on Sept. 25, 2020, as the Bristow Norway-operated aircraft returned to Sola from the West Elara oil installation. About 25 to 30 nautical miles southwest of Sola, as the aircraft was making a descent from 7,000 feet to 1,000 feet, its crew received a caution that the oil pressure on the main gearbox had dropped below 45 psi.
Shortly afterwards, the caution “INPUT/AA #1 HOT” came on, and the crew followed the emergency checklist to put the left engine back to idle.
The oil pressure continued to drop to below 35 psi, and the oil cooler automatically switched off. As the aircraft continued its approach to Sola, the oil temperature rose and the caution “INPUT/ACC #2 HOT” came on. The oil reached a peak temperature of 214 C.
The crew declared mayday as they continued to descend to 200 feet, and were preparing to ditch in the sea if the oil pressure disappeared completely.
However, the aircraft was able to land normally at Sola, and it was followed to a standstill by the airport’s fire and rescue department.
The Norwegian Safety Investigation Authority arrived that evening to begin their investigation into the incident, and found about four liters of oil missing from the main gearbox. The main gearbox normally contains about 30 liters of oil.
Investigators found some oil spill on the left engine and left side of the main gearbox, and there was oil on the outside of the helicopter, particularly on the left side of the fuselage.
They noted that the oil appeared to come from the left engine input to the main gearbox area, but there were no signs of leakage in the oil cooler or its hose connections.
An indicator that warns of a high pressure difference across the oil filter had come out, but the investigators saw no particles during an initial visual inspection of the oil filter, and they found no metal particles on the main gearbox’s magnetic plugs.
The main gearbox has been removed and is to be sent to Sikorsky for further analysis.
The NSIA said it will continue its investigation with help from the U.S. National Transportation Safety Board.
Anybody knowledgable with the 92 care to point out how it currently complies with the CS criteria?
1/ Apparently doesn't meet the "run dry" capability as has been proven in the field and by FAA testing.
2/ Starting to prove that it doesn't meet the remaining criteria for improbability?
Apples to apples you may be better off in a 225!
Apples to apples you may be better off in a 225!
Err, no thanks. :mad:
Really? Using the trite analysis that most people use for analysis the 225 is still safer by a factor of about 3-4?
helicrazi
2nd Oct 2020, 20:57
Really? Using the trite analysis that most people use for analysis the 225 is still safer by a factor of about 3-4?
You know what trite rhymes with, about sums it up....
My thoughts entirely - they both probably rhyme with trite and are as bad as each other.
Don't have to get in either of them and would not anyway, just surprised at the way people perceive things.
DOUBLE BOGEY
3rd Oct 2020, 05:45
We must not forget the basic definition of the helicopter:
”Thousand of parts rotating around an oil leak waiting for metal fatigue to set in”
Statistics...........inevitability!
nowherespecial
4th Oct 2020, 06:08
Genuine question, if the aircraft landed safely, why is the NSIA looking at this? Is it because it is a HiPo event? I'm not surprised they are taking a keen interest but having a team on site etc seems like they want to be in charge. What did I miss?
HeliMannUK
4th Oct 2020, 08:40
4 litres off of 30 is the 13% circa of the total content.
Beside the dispute about meeting the CS requirements and/or dry run capabilities (that is not the second since some oil remained) I was asking myself: how is it possible that a so small loss of oil quantity in the MGB could trigger a so disastrous outcome?
Bad MGB design?
Could anyone help me understand?
Thx.
There was no disastrous outcome. They landed at SOLA.
There was no disastrous outcome. They landed at SOLA. Yes, a good result in that respect but the MRGB is being removed and sent to Sikorsky - engineering-wise that is a disastrous and expensive outcome from just the loss of 12% of its oil.
Yes, a good result in that respect but the MRGB is being removed and sent to Sikorsky - engineering-wise that is a disastrous and expensive outcome from just the loss of 12% of its oil.
I don't want to shout, but the event would NOT have been caused by the loss of 12% of the oil. The oil loss will be a consequence.
My money is on either a mechanical issue in the #1 input module, or a failure of the oil scavange from the #1 input module which then led to "churning". It was overheating of the input module and then partial failure of mating seals between the input module and main module that resulted in some loss of oil.
Of course, I could be wrong ;)
Genuine question, if the aircraft landed safely, why is the NSIA looking at this? Is it because it is a HiPo event? I'm not surprised they are taking a keen interest but having a team on site etc seems like they want to be in charge. What did I miss?
They might want to understand how close to real disaster this was.
Even a ditching (notwithstanding a fatal crash) in cozy Norwegian Winter North Sea conditions is something they would dearly like to avoid, I guess.
helicrazi
4th Oct 2020, 10:34
I don't want to shout, but the event would NOT have been caused by the loss of 12% of the oil. The oil loss will be a consequence.
My money is on either a mechanical issue in the #1 input module, or a failure of the oil scavange from the #1 input module which then led to "churning". It was overheating of the input module and then partial failure of mating seals between the input module and main module that resulted in some loss of oil.
Of course, I could be wrong ;)
I'm struggling to remember where and when but hasnt this churning issue happened before and had a very similar situation.
From AIN online 2011The next-generation gearbox will also feature an automatic oil-cooler bypass switch, unipleat oil filter and improved durability with redundant scavenge and an auxiliary/emergency lubrication system. “The aircraft’s gearbox today already has a lot of redundancy,” Elani said. “We’re adding to that to further improve safety.”
Visual and aural warnings of a drop in oil pressure or a failed oil pump indicator will help pilots and crew in the decision-making process.
so an input module problem can cause a loss of oil and oil pressure so that the engine has to be brought to idle, the bypass to the cooler automatically operates leading to both engine input modules overheating??
Wouldn't be fun further out to sea IMC!
How much longer would it have taken to drop the oil pressure enough for them to ditch?
Surely a system with lots of redundancy would allow continued ops on one engine without problems?
Please shout all you like but I struggle to see how this is a well designed MRGB.
212man
4th Oct 2020, 12:48
I'm struggling to remember where and when but hasnt this churning issue happened before and had a very similar situation.
It was Brunei in 2008 (11:26 on18th Jan to be precise!) The symptoms were a lot more dramatic and rapid though, but possibly because in this event the engine was brought to idle. That was one of several changes that came in as a result (including Adding the INPUT HOT caution).
HeliMannUK
4th Oct 2020, 19:16
From AIN online 2011 so an input module problem can cause a loss of oil and oil pressure so that the engine has to be brought to idle, the bypass to the cooler automatically operates leading to both engine input modules overheating??
From reading the news report the engine was idled due to INPUT ACC HOT #1 caution but that would have been caused by the MGB Oil Cooler being auto bypassed due to loss of oil pressure in the MGB.
afaik
The MGB oil cooler is separate from the MGB so it is a possible oil leak location and that is why it will be automatically bypassed (pressure drop). If the oil pressure drop continues then the bypass can be cancelled as a possible leak is not in the cooler.
I dont think you would need to idle an engine as you would expect 'input acc hot #n' once MGB bypass is activated, you have the APU to fire up to provide electric power if need be if you lose a generator in the accessory, which btw shares oil with the MGB.
Without the proper report coming out we will have to wait and see what actually has occurred (as actually as they can get).
helicrazi
4th Oct 2020, 19:30
From reading the news report the engine was idled due to INPUT ACC HOT #1 caution but that would have been caused by the MGB Oil Cooler being auto bypassed due to loss of oil pressure in the MGB.
afaik
The MGB oil cooler is separate from the MGB so it is a possible oil leak location and that is why it will be automatically bypassed (pressure drop). If the oil pressure drop continues then the bypass can be cancelled as a possible leak is not in the cooler.
I dont think you would need to idle an engine as you would expect 'input acc hot #n' once MGB bypass is activated, you have the APU to fire up to provide electric power if need be if you lose a generator in the accessory, which btw shares oil with the MGB.
Without the proper report coming out we will have to wait and see what actually has occurred (as actually as they can get).
Getting an INPUT ACC HOT by itself would not cause the oil cooler to auto bypass.
There must have been a reduction in pressure to cause the bypass, basically an amber MGB OIL PRESS caption.
Fareastdriver
4th Oct 2020, 20:26
Life was so much simpler in the 1970s with the 330C; just a MGB pressure warning light and an oil temperature gauge..
HeliMannUK
4th Oct 2020, 20:48
Getting an INPUT ACC HOT by itself would not cause the oil cooler to auto bypass.
There must have been a reduction in pressure to cause the bypass, basically an amber MGB OIL PRESS caption.
Exactly, think my post agrees with that.
helicrazi
5th Oct 2020, 05:05
Exactly, think my post agrees with that.
Sorry I must have misunderstood, I thought you were saying the INPUT ACC HOT would trigger the bypass. In that case, we are in agreement :ok:
fuzz burn
7th Oct 2020, 19:21
I don't want to shout, but the event would NOT have been caused by the loss of 12% of the oil. The oil loss will be a consequence.
My money is on either a mechanical issue in the #1 input module, or a failure of the oil scavange from the #1 input module which then led to "churning". It was overheating of the input module and then partial failure of mating seals between the input module and main module that resulted in some loss of oil.
Of course, I could be wrong ;)
Would second this theory, S92 MGB prone to " Churning" Events. Special procedure contained in the AMM to help eliminate under "normal"conditions.
212man
9th Oct 2020, 14:53
Would second this theory, S92 MGB prone to " Churning" Events. Special procedure contained in the AMM to help eliminate under "normal"conditions.
It does seem to have some of the hall marks of a churning event, although there seem to be some missing elements. If the hot oil was causing the INPUT/ACC 2 cautions then there would also have been the MGB HOT caution too. Also, if it was caused by blocked scavenging there would have been an MGB PUMP FAIL caution, I think. This is generated by the drop in pressure in the scavenge line from the input module to the pump in the MGB sump. This modification came in after the first two churning events, along with splitting the sensor cautions from INPUT# CHIP/ACC#CHIP to INPUT#HOT/ACC#HOT as well - same sensor read both indications but only showed CHIP. They also introduced the procedure to bring the engine to IDLE to reduce the energy being put into the oil by the shearing action of the (submerged) gears.
I do find the temperature rise quite low and gentle for a churning event - particularly as the cooler was now in bypass. This must be the result of selecting IDLE and, if it was indeed churning, it's good to see how effective this action is in practice. Hard to imagine oil seals breaking down at 214 C though.
I had the first 'churning event' on the type so have a bit of insight......
GenuineHoverBug
27th Oct 2020, 11:15
Link to the latest update (https://havarikommisjonen.no/Aviation/Investigations/20-836) from NSAI, indicating that a washer has been found in the left-hand input module scavenge oil passageway.
Pi1ot
27th Oct 2020, 11:36
It does seem to have some of the hall marks of a churning event, although there seem to be some missing elements. If the hot oil was causing the INPUT/ACC 2 cautions then there would also have been the MGB HOT caution too. Also, if it was caused by blocked scavenging there would have been an MGB PUMP FAIL caution, I think. This is generated by the drop in pressure in the scavenge line from the input module to the pump in the MGB sump. This modification came in after the first two churning events, along with splitting the sensor cautions from INPUT# CHIP/ACC#CHIP to INPUT#HOT/ACC#HOT as well - same sensor read both indications but only showed CHIP. They also introduced the procedure to bring the engine to IDLE to reduce the energy being put into the oil by the shearing action of the (submerged) gears.
I do find the temperature rise quite low and gentle for a churning event - particularly as the cooler was now in bypass. This must be the result of selecting IDLE and, if it was indeed churning, it's good to see how effective this action is in practice. Hard to imagine oil seals breaking down at 214 C though.
I had the first 'churning event' on the type so have a bit of insight......
Regarding the temperature, it is likely that 214 C was the lowest (the oil is supposed to cool the MGB). There is also an unconfirmed rumor about smoking hot MGB after landing, and that the fire crew measured an external temperature of close to 300 C.
212man
27th Oct 2020, 15:45
Regarding the temperature, it is likely that 214 C was the lowest (the oil is supposed to cool the MGB). There is also an unconfirmed rumor about smoking hot MGB after landing, and that the fire crew measured an external temperature of close to 300 C.
Ok could be. I can confirm the input module does get smoking hot - mine was black and blistered and the cabin was full of smoke. It smelt like we were in a welding workshop! They modified the software after to register higher temperatures than previously calibrated - our gauge went blank at a certain point.
A washer in the scavenge line will definitely cause churning.
A washer in the scavenge line
QA system is working fine then? Still have the view that the S92 is a "kludge" designed by a committee.
So long as that is understood - you will be fine.
megan
28th Oct 2020, 00:58
All aircraft, ships, cars are designed by committees - engineers for stress, aerodynamics, electrics, hydraulics, undercarriage, instrumentation etc etc etc, though one man/woman is designated the boss
So long as that is understood - you will be fine ;)
Paul Cantrell
28th Oct 2020, 16:01
Anybody knowledgable with the 92 care to point out how it currently complies with the CS criteria?
1/ Apparently doesn't meet the "run dry" capability as has been proven in the field and by FAA testing.
2/ Starting to prove that it doesn't meet the remaining criteria for improbability?
So what's the process for kicking off a review if indeed events are showing certification criteria for probability of an in flight failure are indeed not being met? Presumably that would be the governmental body that originally certified the aircraft? What actually triggers such a review? ( or do a crew and passengers have to lose their lives before someone starts a review? ) Any chance Sikorsky is working in the background to do a true run dry design, in anticipation that someone might try to ground their aircraft? Serious question despite my somewhat snarky parenthetical remark...
212man
28th Oct 2020, 17:42
Any chance Sikorsky is working in the background to do a true run dry design
not in the background - they announced the 92B and A+ last year. The later is an upgraded A that includes the phase IV MGB, which they advertise as exceeding the 29.927 requirements. They ran it without oil for the equivalent of 500nm at 80 kts, they say.
Apate
29th Oct 2020, 07:30
not in the background - they announced the 92B and A+ last year. The later is an upgraded A that includes the phase IV MGB, which they advertise as exceeding the 29.927 requirements. They ran it without oil for the equivalent of 500nm at 80 kts, they say.
Of course the true "loss of oil" capability will be a huge step forward. However this event highlights that the MGB design also needs to have redundant scavange capability, as the small loss of oil in this case was a consequence rather than the cause. The phase IV MGB press releases don't mention if this is part of the redesigned box, although it has been mentioned many times by Sikorsky in the past as an aim.
212man
29th Oct 2020, 12:29
Of course the true "loss of oil" capability will be a huge step forward. However this event highlights that the MGB design also needs to have redundant scavange capability, as the small loss of oil in this case was a consequence rather than the cause. The phase IV MGB press releases don't mention if this is part of the redesigned box, although it has been mentioned many times by Sikorsky in the past as an aim.
Yes, the loss of oil in this event is irrelevant and I was not referring to it at all - simply to the question posed by Paul Cantrell. In fact, the symptoms of this type event are caused by too much oil! The input module fills up and immerses the gears, resulting in huge shearing forces being applied across the oil which heats up very rapidly. The procedure to reduce the engine to idle is to reduce the amount of energy being imparted into the oil, so reduces the rate of heating but does not stop it.
Jimmy.
29th Oct 2020, 18:33
not in the background - they announced the 92B and A+ last year. The later is an upgraded A that includes the phase IV MGB, which they advertise as exceeding the 29.927 requirements. They ran it without oil for the equivalent of 500nm at 80 kts, they say.
If I'm not wrong, they ran it without both main pumps (the new system is supposed to have an emergency pump on the sump, like in the S61) for the equivalent of 500NM at 80 kts. Nice feature, but doesn't address the run dry nor the temperature increase after bypass...
212man
29th Oct 2020, 19:43
If I'm not wrong, they ran it without both main pumps (the new system is supposed to have an emergency pump on the sump, like in the S61) for the equivalent of 500NM at 80 kts. Nice feature, but doesn't address the run dry nor the temperature increase after bypass...
this is from their website - seems to imply no oil:
Notably, both configurations will include the Phase IV main gearbox. This gearbox has been validated to exceed the requirements of CFR 29.927(c) as demonstrated by full-scale testing witnessed by the FAA. All of the primary lubrication system oil was removed prior to operating the gearbox for the equivalent of over 500 nautical miles of flight at an airspeed of 80 knots. No discernable anomalies were identified during the post-test examination.
It doesn’t expand on what ‘secondary lubrication’ might be....
Jimmy.
29th Oct 2020, 21:31
https://www-ainonline-com.cdn.ampproject.org/c/s/www.ainonline.com/aviation-news/gene
"During ground testing, the gearbox ran for more than seven hours and the test was halted only when the engineers got to the time when the helicopter would have run out of a full load of fuel. The new “Phase IV” gearbox was also flown for more than 200 flight hours and also later torn down and inspected in the presence of the FAA.
Notably, the design uses a supplemental fuel pump and additional oil lines to reuse main gearbox oil that is accumulated in a lower sump in the event of primary lubrication failure. While some other OEMs have developed “run dry” gearboxes that can function for between 30 and 50 minutes without primary lubrication, Sikorsky found this of dubious value given the offshore distances some of its customers must fly.
When secondary lubrication kicks in, the event generates a “technical indicator” back to Sikorsky to facilitate troubleshooting once the impacted helicopter lands or returns to base. Brady said customers greeted the new gearbox enthusiastically and want it “as soon as possible.”
As I've said, nice feature, but if flying along with a MGB BYPASS and the ECL stating to don't put that switch in MAN COOL, I would be very concerned about that temperature bar rising on my EICAS if not just few miles away.
the design uses a supplemental fuel pump and additional oil lines to reuse main gearbox oil that is accumulated in a lower sump in the event of primary lubrication failure so they have just reinvented the ELS system from the Sea King except using a fuel pump instead of the Tqmeter pump. - not exactly a 21st century solution.
HeliMannUK
2nd Nov 2020, 11:21
I dont think the accessories can last that long without oil but still flying on the APU & backup hyd is better than not flying. Maybe the supplemental supplies oil to the accessories?
Phil Kemp
2nd Nov 2020, 17:18
so they have just reinvented the ELS system from the Sea King except using a fuel pump instead of the Tqmeter pump. - not exactly a 21st century solution.
No, they have just installed the very same system that was used very successfully on the S61N for over 45 years.
3D CAM
2nd Nov 2020, 19:07
so they have just reinvented the ELS system from the Sea King except using a fuel pump instead of the Tqmeter pump. - not exactly a 21st century solution.
Remind me how long it took Wastelands to develop a system for the Sea King that was already in use on the S61?...and had been from the mid 70's.
I am not standing up for Sikorsky on this, this problem should have been sorted out years ago.
Phil Kemp, you beat me to it.
3D CAM
Yes Wastelands were doing what they do best - waiting to see how much they could charge the customer for providing something that should have been there in the first place.
Either way, the S-92 'fix' isn't new technology and adds extra pipes and complexity that they claimed was what they had eliminated with the original design of the MRGB.
212man
3rd Nov 2020, 15:14
I dont think the accessories can last that long without oil but still flying on the APU & backup hyd is better than not flying. Maybe the supplemental supplies oil to the accessories?
I think if you reached the stage where the AC Gens and 1/2 hydraulic pumps have mechanically failed due to lack of lubrication, you have really stretched your luck!
I can say, though, that during prolonged churning the AC Gens will trip offline due to overheating (being normally cooled by the MGB oil). We lost No 1 and I don’t know how long No 2 would have stayed online. This then revealed a stuck AC bus relay, so No 1 AC bus dropped offline and took the No 1 and Backup DC Converters with it.