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Turbomeca Arrius 2B1_A1 failure in our helicopter #2745290
09/16/12 09:24 AM
09/16/12 09:24 AM
Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Cujet Online content OP
Cujet  Online Content OP

Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
We operate a 2001 Eurocopter EC-135 with Turbomeca engines. They are hard working, lightweight engines and as such, don't exhibit the typical supreme turbine reliability you might expect. A typical problem with this engine is a cracking "aft turbine bearing" oil feed line. This causes leaking oil to get all over the hot section parts and creates a problem. In our case, the lower oil line clogged due to coking. While I did not see any cracks, there was plenty of evidence of internal leakage. (they use compression fittings and these have been a problem too)

Enjoy:







Obviously, the oil is coking. We have been using BP2380, which is a standard turbine engine oil and it meets the requirements of the engine manufacturer. Many operators use Mobil Jet II, which is quite similar and will coke just as rapidly.

There is another option. Mobil 254. It is a HTS (high thermal stability) oil. However, the Turbomeca tech cautioned me about using it. 254 is creating problems with the "O ring" material used in these (and Pratt Whitney) engines. The deterioration over time and subsequent leakage is bad enough to warrant a prohibition of 254 oil on certain Pratt engines. However, it is OK to use and meets the requirements of this Turbomeca engine. I'm not sure yet which way I want to go.


People who count on their fingers should maintain a discreet silence.
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #2745301
09/16/12 09:28 AM
09/16/12 09:28 AM
Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Cujet Online content OP
Cujet  Online Content OP

Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Almost forgot,

The engine has 899 hours since new and 668 hours since overhaul. It's not a high time engine. This problem took 668 hours to occur. That's not great.

The engine on the other side is producing rated power within the RPM and Temp upper limits, by the slimmest of margins (at 937 hours total time since new) . In other words, it's airworthy, but needs to be looked after carefully. It won't be long before that engine comes off for overhaul.


People who count on their fingers should maintain a discreet silence.
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #2745302
09/16/12 09:29 AM
09/16/12 09:29 AM
Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Cujet Online content OP
Cujet  Online Content OP

Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Marvel Mystery oil to clean out the sludge and carbon??

(ha ha, just a joke)


People who count on their fingers should maintain a discreet silence.
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #2745313
09/16/12 09:40 AM
09/16/12 09:40 AM
Joined: May 2011
Posts: 149
usa
cathy Offline
cathy  Offline

Joined: May 2011
Posts: 149
usa
how reliable are helicopters


97 camry.
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #2745334
09/16/12 10:00 AM
09/16/12 10:00 AM
Joined: Sep 2004
Posts: 22,884
Central Florida
Mr Nice Offline
Mr Nice  Offline

Joined: Sep 2004
Posts: 22,884
Central Florida
Poor design ?

Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #2745337
09/16/12 10:00 AM
09/16/12 10:00 AM
Joined: Oct 2008
Posts: 19,445
Sunny Florida
SteveSRT8 Offline
SteveSRT8  Offline

Joined: Oct 2008
Posts: 19,445
Sunny Florida
Wow! I would expect a longer life, or at least hope for it.

That's a heck of an issue. They need to update that seal material and allow more choices in oils. Any oil that leaks into the combustion zone will coke up too, right?


"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #2745356
09/16/12 10:13 AM
09/16/12 10:13 AM
Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Cujet Online content OP
Cujet  Online Content OP

Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Mobil 254 has been around seemingly forever. Like you, I can't understand why turbine engine manufacturers don't design around such oils.

Clearly, this was a safety of flight issue. And, clearly, 254 oil would have fully prevented the issue. Possibly, there may be no "O ring" material that's good enough under these temperatures with 254.

I'd say it's poor design alright. Our Rolls Royce engines have bearing areas that are cooled by a flood of filtered air. These types of problems are non existent on the RR engines.


People who count on their fingers should maintain a discreet silence.
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: cathy] #2745365
09/16/12 10:20 AM
09/16/12 10:20 AM
Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Cujet Online content OP
Cujet  Online Content OP

Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Originally Posted By: cathy
how reliable are helicopters


Very reliable, when properly maintained and flown responsibly. The good news is that this is a twin engine helicopter. With one engine shut down, the other engine is "allowed" to make up most of the lost power.

60% torque, each engine in normal ops. 119% torque from one engine in OEI (one engine inoperative) conditions. Put simply, one is as powerful as two, if needed.

This particular helicopter has been a maintenance nightmare. But, that's mostly from a parts/logistics point of view, NOT an operational point of view. We've never had any serious "in flight" problems over 11 years of ops. In fact, we've had few in flight squawks at all. Most of them are found by maintenance before they become a problem.

However, there have been many, many changed parts. Due to wear, harsh environment, cracks, coking, AD's, and so on.

You've all seen this before, but just in case, this is the heli:


Last edited by Cujet; 09/16/12 10:21 AM.

People who count on their fingers should maintain a discreet silence.
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #2745826
09/16/12 07:55 PM
09/16/12 07:55 PM
Joined: Oct 2002
Posts: 37,632
Great Lakes
Quattro Pete Offline
Quattro Pete  Offline

Joined: Oct 2002
Posts: 37,632
Great Lakes
Troublemeca, eh? smile

I flew on an EC130 over the Victoria Falls last summer. Nice machine, at least to a helicopter newbie like myself. smile


'02 530i (Edge 0W-40)
'15 Q5 3.0T (Edge 5W-40)
'18 Charger SRT (PUP 0W-40 SRT)
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #2746230
09/17/12 09:20 AM
09/17/12 09:20 AM
Joined: Jul 2006
Posts: 2,198
Virginia
Tom NJ Offline
Tom NJ  Offline

Joined: Jul 2006
Posts: 2,198
Virginia
Originally Posted By: Cujet
Obviously, the oil is coking. We have been using BP2380, which is a standard turbine engine oil and it meets the requirements of the engine manufacturer. Many operators use Mobil Jet II, which is quite similar and will coke just as rapidly.

There is another option. Mobil 254. It is a HTS (high thermal stability) oil. However, the Turbomeca tech cautioned me about using it. 254 is creating problems with the "O ring" material used in these (and Pratt Whitney) engines. The deterioration over time and subsequent leakage is bad enough to warrant a prohibition of 254 oil on certain Pratt engines. However, it is OK to use and meets the requirements of this Turbomeca engine. I'm not sure yet which way I want to go.


BP 2380 is a fine oil but probably the worse with respect to coking. It is an older 2nd generation oil (1960s) and can cause coke due to it's high concentration of dipentaerythritol and longer acids in the polyol ester base oils. Mobil Jet II is also 2nd generation but a bit better on coking due to a more stable base oil.

MJ254 is a 3rd generation turbine oil that uses the same base ester as MJ II and has a polymerized amine anti-oxidant that helps a lot with coking propensity, but as you say can have adverse effects on fluorocarbon seal materials at high temperatures.

BP 2197 is a 4th generation turbine oil and generally acknowledged as the cleanest readily available oil for coking. It uses a patented advanced (more stable) polyol ester base oil along with a polymerized amine anti-oxidant, and is the oil of choice for hotter running modern engines. It also, however, has a fluorocarbon "O ring" issue.

ExxonMobil has a new 4th generation oil called MJ 387 going through the approval process that claims to be seal friendly, but I do not know the composition.

Perhaps more interesting is a new 4th generation low coking oil from Shell called "Ascender". This oil uses an advanced polyol ester base oil and a unique patented anti-oxidant system that is seal friendly. It is also still in the approval process.

I should note that the O ring seal manufacturers are working on new seal compositions that work better with the polymerized amine anti-oxidants.

Of course if you have an oil leak spraying oil over hot engine parts, even 4th generation oils may not be the full cure, but should help.

Tom NJ

Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Tom NJ] #2753073
09/24/12 10:17 AM
09/24/12 10:17 AM
Joined: Jan 2011
Posts: 5
CT
Runner Offline
Runner  Offline

Joined: Jan 2011
Posts: 5
CT
Agree with Cujet and Tom NJ that HTS (high thermal stability) oil worth investigating. In fact, Turbomeca has a Service Letter (No. 2618/08/ARRIUS2B/46) recommending the use of HTS oil in engines used in EMS applications to prevent oil coking and subsequent in-flight shut down. While your application may not be as demanding as an EMS mission, your symptoms are consistent.

A side note on elastomer seals: some Pratt & Whitney (Canada) engines do have issues with HTS oils, but the seal material, seal supply source and time between overhaul are all factors that make that situation different than Turbomeca's. Note that Turbomeca goes out of its way to recommend HTS oil for the Arrius 2B.

Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Runner] #3170272
10/28/13 01:46 PM
10/28/13 01:46 PM
Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Cujet Online content OP
Cujet  Online Content OP

Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Originally Posted By: Runner
Agree with Cujet and Tom NJ that HTS (high thermal stability) oil worth investigating. In fact, Turbomeca has a Service Letter (No. 2618/08/ARRIUS2B/46) recommending the use of HTS oil in engines used in EMS applications to prevent oil coking and subsequent in-flight shut down. While your application may not be as demanding as an EMS mission, your symptoms are consistent.

A side note on elastomer seals: some Pratt & Whitney (Canada) engines do have issues with HTS oils, but the seal material, seal supply source and time between overhaul are all factors that make that situation different than Turbomeca's. Note that Turbomeca goes out of its way to recommend HTS oil for the Arrius 2B.


I've been looking for that SL for some time now. I don't have it in my book.

Anyway, I've spoken with a number of different Turbomeca tech reps. None have recommended the HTS oils. All of them say the same thing, if you want leaks and early teardown for leak repair, use an HTS oil.

I wonder why the discrepancy? Possibly the operators information is more current than the Service Letter.


People who count on their fingers should maintain a discreet silence.
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #3171218
10/29/13 09:39 AM
10/29/13 09:39 AM
Joined: Jul 2006
Posts: 2,198
Virginia
Tom NJ Offline
Tom NJ  Offline

Joined: Jul 2006
Posts: 2,198
Virginia
As Runner noted above, the oil composition is only one factor, and the seal composition, seal manufacturer, and operating conditions are others. The seal issue with some seals and some HTS oils is related to the anti-oxidants used in the oil, which varies with different oils, so Turbomeca's position against all HTS oils is not justified. HTS oils have been around for over 30 years and make up a large and still growing percentage of the turbine oils in commercial airline use. Clearly not everyone is having seal issues.

Just FYI, HTS (High Thermal Stability) is a low coking performance designation used in the US Military specification MIL-PRF-23699. On the commercial airline side, the appropriate specification is AS5780B which uses the designation HPC (High Performance Capability) for such oils. The AS5780B specification encompasses the MIL-PRF-23699 specification, but includes additional and more severe tests, limits, and controls. This includes more severe tests for both coking and elastomer compatibility, so you may wish to look into oils approved under AS5780B, HPC class.

Here is some additional reading on the subject:

Fluorocarbon O-ring Compatibility with Aircraft Engine Lubricating Oils

Shell Ascender

Tom NJ

Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #3171261
10/29/13 10:06 AM
10/29/13 10:06 AM
Joined: Jun 2002
Posts: 20,234
Iowegia - USA
MolaKule Offline
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Iowegia - USA
Originally Posted By: Cujet
Mobil 254 has been around seemingly forever. Like you, I can't understand why turbine engine manufacturers don't design around such oils.

Clearly, this was a safety of flight issue. And, clearly, 254 oil would have fully prevented the issue. Possibly, there may be no "O ring" material that's good enough under these temperatures with 254.

I'd say it's poor design alright. Our Rolls Royce engines have bearing areas that are cooled by a flood of filtered air. These types of problems are non existent on the RR engines.


No one has mentioned the oil cooling circuit design of this engine.

In order for turbine oil to really coke like that it must have been exposed to high temperatures somehow near or in the hot section, and I suspect the bulk oil temps are way higher than they should be.

If I were the engine designer(s), I would revisit 1) the design of the oil cooling system, 2) oil paths and components (such as those bearing cells near the hot section), because this lubricant is seeing high temps beyond it's capabilities.

Last edited by MolaKule; 10/29/13 10:18 AM.

"Science is a body of knowledge, a 'recipe', as it were, for reality. The totality of science is a collection of hard-earned nuggets, using math as a language of expression." Chip Cohen
Re: Turbomeca Arrius 2B1_A1 failure in our helicopter [Re: Cujet] #3171329
10/29/13 11:04 AM
10/29/13 11:04 AM
Joined: Feb 2003
Posts: 8,554
Jupiter, Florida
Cujet Online content OP
Cujet  Online Content OP

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Posts: 8,554
Jupiter, Florida
The oil cooler system is sufficient to keep sump temperatures in the "green". Next time I fly, I'll take note of the actual indicated temp. It's always in the middle of the green and not near any limits.

The oil coolers are force fed by very powerful blowers.

The oil coking occurs in the rear bearing chamber, right in the middle of the hot section. Bad design, possibly insufficient oil flow, but not elevated overall oil temps.


People who count on their fingers should maintain a discreet silence.
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