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Bristow emergency landing

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Bristow emergency landing

Old 4th Oct 2020, 20:26
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Life was so much simpler in the 1970s with the 330C; just a MGB pressure warning light and an oil temperature gauge..
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Old 4th Oct 2020, 20:48
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Originally Posted by helicrazi
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.
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Old 5th Oct 2020, 05:05
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Originally Posted by HeliMannUK
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
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Old 7th Oct 2020, 19:21
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Churning

Originally Posted by Apate
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.
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Old 9th Oct 2020, 14:53
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Originally Posted by fuzz burn
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......
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Old 27th Oct 2020, 11:15
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Brief update on the investigation

Link to the latest update from NSAI, indicating that a washer has been found in the left-hand input module scavenge oil passageway.
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Old 27th Oct 2020, 11:36
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Originally Posted by 212man
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.
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Old 27th Oct 2020, 15:45
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Originally Posted by Pi1ot
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.
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Old 27th Oct 2020, 18:23
  #49 (permalink)  
 
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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.
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Old 28th Oct 2020, 00:58
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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
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Old 28th Oct 2020, 16:01
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Originally Posted by RVDT
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...
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Old 28th Oct 2020, 17:42
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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.
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Old 29th Oct 2020, 07:30
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Originally Posted by 212man
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.
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Old 29th Oct 2020, 12:29
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Originally Posted by Apate
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.
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Old 29th Oct 2020, 18:33
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Originally Posted by 212man
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...
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Old 29th Oct 2020, 19:43
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Originally Posted by Jimmy.
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....

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Old 29th Oct 2020, 21:31
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https://www-ainonline-com.cdn.amppro...tion-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.
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Old 30th Oct 2020, 07:01
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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.
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Old 2nd Nov 2020, 11:21
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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?
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Old 2nd Nov 2020, 17:18
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Originally Posted by [email protected]
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.
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