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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Originally Posted by helicrazi
(Post 10898249)
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. |
Originally Posted by HeliMannUK
(Post 10898283)
Exactly, think my post agrees with that.
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Churning
Originally Posted by Apate
(Post 10897999)
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 ;) |
Originally Posted by fuzz burn
(Post 10900052)
Would second this theory, S92 MGB prone to " Churning" Events. Special procedure contained in the AMM to help eliminate under "normal"conditions.
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...... |
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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Originally Posted by 212man
(Post 10901286)
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...... |
Originally Posted by Pi1ot
(Post 10912729)
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.
A washer in the scavenge line will definitely cause churning. |
A washer in the scavenge line So long as that is understood - you will be fine. |
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 ;) |
Originally Posted by RVDT
(Post 10897099)
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? |
Any chance Sikorsky is working in the background to do a true run dry design |
Originally Posted by 212man
(Post 10913665)
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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Originally Posted by Apate
(Post 10914044)
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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Originally Posted by 212man
(Post 10913665)
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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Originally Posted by Jimmy.
(Post 10914537)
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...
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. |
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. |
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 |
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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Originally Posted by [email protected]
(Post 10914823)
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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