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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 4th Nov 2010, 17:30
  #681 (permalink)  
 
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In response to false suggestions namely
a) there is a lot of nonsense on PPRuNe. Of course there is but on this matter a number of S-92 critics were spot on before the accident
b) that Sikorsky had not mislead anyone. They did and that is clear.

I agree on most of what you say. The exception are
a) that Sikorsky may have cured one oil loss location but what about the rest?
b) extra oil is only good if it is not pumped out over board at 50l/min or whatever the S-92 pump rate is
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Old 5th Nov 2010, 12:42
  #682 (permalink)  
 
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again......

I.I the statement 'realistically impossible' statement is incorrect, the AW139 and EH101 prove it is possible and that the FAR requirement can be met in full.

A supplementary lubrication system just means you dump that oil overboard as well.

DM
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Old 5th Nov 2010, 13:29
  #683 (permalink)  
 
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DM

It depends on where the leak is and how large the discharge is. I was thinking more in terms of a loss supplementary system similar to the glycol system on the EC225.

Yes the 101 has run dry but it's not used in the commercial world. So does the UH-60.

That leaves the 139 as the sole current commercial helicopter with certified run dry capability, good on AW for achieving it.

Last edited by industry insider; 5th Nov 2010 at 13:46.
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Old 5th Nov 2010, 13:54
  #684 (permalink)  
 
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industry insider:
Yes the 101 has run dry but it's not used in the commercial world. So does the UH-60.
In light of the fact that the S-92 transmission self-destructed after about 10 minutes of running without oil, and the UH-60 has basically the same transmission design...

The question was asked of me in PMs whether the UH-60 actually has this mythical "run-dry" capability either?

And frankly, I did not know (although I should have). So I put the question out there: Is there an emergency lubrication system or other such device that the UH-60 transmission employs to provide and allow this "30-minute run-dry capability?" If not, how do they do it?
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Old 5th Nov 2010, 19:10
  #685 (permalink)  
 
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wrong, wrong, wrong

The EH101 was civil certified WITH a 30 minute capability in 1994, (EH101-300 and -500 series aircraft) by the CAA, FAA and RAI.

This was amended in 1998 (?) for the -510 variant which the Tokyo police force are still flying as a civil registered aircraft that is fully comliant with the relevant civil regulations.

regardless the same transmission is in use with military 101s with the same 30 minute capability (anybody here got access to a set of Merlin FRCs?)

so it's not just the 139

DM
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Old 5th Nov 2010, 21:36
  #686 (permalink)  
 
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Aaah
That would explain why in the run up to the Presidential helicopter bid Sikorsky's Project Director wouldn't admit the shortcoming.
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Old 5th Nov 2010, 22:09
  #687 (permalink)  
 
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And they only flew a couple of minutes longer than our crew in Australia the year before. I bet those guys feel really lucky.
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Old 6th Nov 2010, 00:13
  #688 (permalink)  
 
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ironchefflay:
the MGB on the crashed aircraft did not lose main rotor drive. the main rotor was still turning on impact. you all seem to be avoiding that fact. along with the fact that the engines were shut down and the aircraft appeared to be flaring to ditch. still under control very possibly.
You talking about Cougar? If the engines were off, it is because their tail rotor drive gear in the MGB failed. That is a fact.
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Old 6th Nov 2010, 09:42
  #689 (permalink)  
 
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DM

Yes I KNOW the 101 is civil certified, I was involved on the fringes of its civilian NS trials. I also KNOW that it is used on one or two civil registers here and there. I didn't mean to imply that it was military only. However it's not in regular commercial use like the other types here.

FH

The UH-60 was designed to run dry after taking hostile fire. While the S-92 MGB is based on the UH-60 MGB there are bigger differences than was initially intended.
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Old 6th Nov 2010, 12:23
  #690 (permalink)  
 
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industry insider:
The UH-60 was designed to run dry after taking hostile fire. While the S-92 MGB is based on the UH-60 MGB there are bigger differences than was initially intended.
I love a good non-answer! I guess the similarities or differences between the UH-60's trans and the S-92's vary depending on who's doing the talking.
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Old 6th Nov 2010, 13:33
  #691 (permalink)  
 
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Not meant to be a non answer, the differences arose because of the heavier MTOW and higher horsepower of the S-92 versus the Hawk. According to Sikorsky, the "architecture" whatever that means is the same but the S-92 box is bigger.
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Old 7th Nov 2010, 17:34
  #692 (permalink)  
 
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One thing that can not be disputed as it is a simple law of physics is that a lot more power at about the same rpm means a lot more torque and a lot more heat.
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Old 8th Nov 2010, 20:53
  #693 (permalink)  
 
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I love a good non-answer! I guess the similarities or differences between the UH-60's trans and the S-92's vary depending on who's doing the talking.
The transmission on the S-92A and the H-60 series are similar like the transmission on a Lincoln Town Car is similar to the transmission on an F-150 pickup truck. They are made by the same company, and they deliver rotary engine power to the wheels (rotors). They don't look remotely the same, they aren't interchangeable and they don't do the same thing in many ways.
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Old 8th Nov 2010, 22:42
  #694 (permalink)  
 
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In principle the all of the dynamic components on the S-92 were designed with the capability for being back fitted onto Blackhawk models. Operating RPM was increased 5% from the Blackhawk’s 258 rpm to allow for some portion of the increase in required ESHP. Other configuration changes were required to accommodate the relocation of primary servos. Some changes were required as a result of the S-92’s weight growth from its proposed 1993 MGW of 22220 lbs. to it present gross weight of 26500 lbs.
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Old 14th Nov 2010, 19:13
  #695 (permalink)  
 
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I've been reading the RFM extract originally posted by HC in April 2005
http://www.pprune.org/rotorheads/365...ml#post6036981

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.
It does look a bit more complex then anything similar for the EC & AW products I'm most familiar with. Why the comment about the APU?

It also makes no mention of pressures below 35psi other than continued pressure drops should lead to landing immediately. Was this changed after ther April 2005 near-ditching in Norway?
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Old 14th Nov 2010, 21:39
  #696 (permalink)  
 
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"Why the comment about the APU?"

The answer's there in the CAUTION. The gearbox driven AC generators are cooled by gearbox oil and may fail. Wouldn't it be nice to still have full electrical power supplied by the APU generator? For all the criticism of the S92 it is particularly strong on redundant systems.
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Old 14th Nov 2010, 21:54
  #697 (permalink)  
 
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Inputshaft

that redundant - TSB reported a power interuption to the FDR, just before the very non redundant tail rotor take off failed.

Sox6

The structure of the checklist buries the actions associated with this failure deep within the checklist.

You are correct there is no warning or clear criteria prior to needing to ditch, especially in light of the late 2008 Sikorsky Safety Advisory that was written to stop ditchings due to vespel spline failures that could cause the oil pressure to drop from 55 psi to just about 7 psi and caused 3 prior emergency landings (1 x Norway, 2 x Brunei).
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Old 14th Nov 2010, 22:14
  #698 (permalink)  
 
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I am sure 212man will be along shortly (when he wakes up!), but in the mean time I am fairly sure that the emergency landings in Borneo were not as a result of low oil pressure - rather it was the churning thing as a result of too much oil in the wrong place, causing the oil to drastically overheat.

In other words Zalt, demonising the S92 is of course good (if rather easy) sport but one should try to get the facts right, otherwise the impact is lost!

But as a general point it would be interesting for us non-92 pilots to know how easy it is to detect 5 psi as opposed to zero psi. I presume there is a digital readout of the pressure under the bargraph, but that is only as good as the sensor accuracy. My point being, do you always see 0 psi when shutdown, or is it sometimes 1 or 2 due to sensor zero offset?

HC

ps I think the APU has a fairly limited output, not sure if it supplies the entire aircraft's systems (though you would think it would supply the CVFDR). Alternatively perhaps the g switch activated in response to high vibration and shut it off?
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Old 14th Nov 2010, 22:22
  #699 (permalink)  
 
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Sox 6, I'm not sure where the quote above comes from, but this is the relevant extract from the RFM. It's the 2005 version so it was in place at the time of the accident. My bold emphasis.

If the MGB OIL PRES warning or the MGB OIL PRES caution and any of the following secondary indications of gearbox
failure are observed:

MGB oil pressure below 5 psi
Smoke or fumes in the cabin
Any subsequent hydraulic system failure
Progressively increasing power required to maintain flight
Unusual vibrations or noises.
6. Land immediately.
HC is correct - although both our events had some low pressure associated with them, they were not "loss of oil" incidents.
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Old 14th Nov 2010, 22:30
  #700 (permalink)  
 
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212man

I'm happy to be corrected as the history of failed vespel spline product improvements is rather, erm, 'complex', but I know we can agree that the Norsk case was low oil pressure.

The checklist linked to earlier today was posted by HC in April 2005 just after the Norsk incident. I assume it is an earlier version to yours (repeated below).

Quote:
If the MGB OIL PRES warning or the MGB OIL PRES caution and any of the following secondary indications of gearbox
failure are observed:

MGB oil pressure below 5 psi
Smoke or fumes in the cabin
Any subsequent hydraulic system failure
Progressively increasing power required to maintain flight
Unusual vibrations or noises.
6. Land immediately.
However is your issue pre or post the Norsk event?

I only ask because this could reinforce the point of Sikorsky tinkering with the RFM (to change "If MGB oil pressure continues to decrease" to "MGB oil pressure below 5 psi" to avoid reasons to ditch (in response to less critical gearbox failure modes) prior to the Broome & Newfie events.

I can see how some crews, reading an evolving RFM, without the benefit of frank insight to the S-92A service experience might have assumed this was asign of greater confidence in the MGB, not as was the case, less.

But if neither of the two Shell events were low oil pressure, what triggered the landings into jungle clearings?

I didn't think it was smoke in the cockpit from the leaking seals of the input module which overheating due to churning. But perhaps it was. Certainly with the checklist above, high oil temperature is not a reason to land immediately, while the sounds of a potentially immenent gearbox failure are. Hardly a design sucess either way.

HC makes a good point on the tolerance of MGB pressure gauges and the difficult call crews have had to make.


It would also be nice to hear if anyone is prepared to comment on Shell Management's claims the S-92A was 'non-preferred' for a time.http://www.pprune.org/rotorheads/163...ml#post6043644
I'm waiting for feedback from my own sources in Shell on that one.

Last edited by zalt; 14th Nov 2010 at 22:48. Reason: Simultaneous posting
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