CFM International and Honeywell have issued service bulletins to engine operators to overcome compatibility problems with Mobil Jet Oil 291, a synthetic lubricant produced by ExxonMobil.
Swiss International Air Lines has had to overhaul 23 of the Honeywell LF507-1F turbofans on its BAE Systems Avro RJs three months early because of oil problems.
The Swiss carrier says carbonisation in the oil system, particularly in valves and seals, was found during routine checks. Honeywell, one of several manufacturers that has certificated MJO291 for use in its engines, says it is "working aggressively" with Swiss and other customers to address the issue. Swiss says the oil problem has affected dispatch reliability and there have been "a few cancelled flights", but no in-flight shut downs.
ExxonMobil describes MJO291 as a fourth-generation synthetic lubricant that has "superior thermal and oxidation stability". Honeywell says the oil was certified after extensive testing, but adds: "Recently, concerns have developed regarding the long-term compatibility of the oil with certain engine components."
Honeywell issued a letter last September warning operators of its ALF502 and LF507 engines of the potential incompatibility with MJO291. Investigation revealed that the clogged oil filter warning indicator could fail due to deterioration of the internal diaphragm caused by contact with MJO291. The letter advised operators to change oil filters every 1,000h.
CFMI, meanwhile, has issued a service bulletin to CFM56 operators warning them to inspect oil systems for leakage after fluorosilicons in the new oil began causing corrosion of O-rings in the system. "We are basically saying if you haven't used the oil don't. If you have already been using it, keep an eye open for leaks," says the company.
General Electric says it has no reports of problems affecting GE engines, but adds it "has not got a handle yet on the extent of the issue with CFM [engines]".
Source: Flight International
