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.
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.