View Full Version : filings of metal in oil - how come?

8th Oct 2009, 21:28
Evening all, the oil differential pressure indicator at our CJ1+ popped out; mechanic exchanged the oil filter and took an oil sample. Analysis showed filings of metal in the oil (btw, small pieces of metal could also be seen with the bare eye at the magneto before the oil filter). Now, the gearbox and oil cooler have to be exchanged. As the engines are relatively new (580 hours, 557 cycles), I was wondering about the cause of that. For usual wear and tear, it seems to be too soon. Any ideas?

Thanks for your input,

8th Oct 2009, 22:09
not familiar with the aircraft type but usually metallurgic analaysis of metal chips can identify which bearings are damaged. sometimes these chips can be fine but dependant on size and origin components might need to be changed.
as for the oil cooler maybe it is possible that this part becomes contaminated with chips and is recommended to be changed also..
i'm sure the maintenance chief will be able to give exact reason.. mechanics usually don't change parts for nothing.

non iron
8th Oct 2009, 23:18
never mind too soon, with visual evidence, it seems like too late to me.

when was is it last checked properly ?

for bearings to hand in their dinner pale the engine has been abused.

9th Oct 2009, 01:43
The oil cooler has to be changed to prevent contamination of the new module being fitted.

May pay to see if you can get a scavenge oil filter kit fitted, prevents contamination of oil cooler and tank.


9th Oct 2009, 13:00
sometimes the metal flakes come from the gear teeth in gear box.
RB211 from the thrust bearing and engine would be changed quickly.
on new engines get build debris from screw threads and bits being rubbed off.
on one engine that had been built incorrectly and discs and things where rubbing so much that the metal flakes blocked up the oil pipes on return pipes and oil was forced out of engine and tank emptied, did not have to count the number of little flakes and chips as when the magnetic chip detector when removed to look at the collection of debris, a mass of filings fell to the ground to many to count.
If oil gets too hot lumps of carbon turn up in the filters.

9th Oct 2009, 16:23
Check the MM. Some engines may permit a drain & flush (maybe multiple drain & flush) - but I wouldn't push the issue if it's not a recognized MM procedure.

Also check the filings with a magnet - that will probably make a difference.

Good luck!

9th Oct 2009, 18:56
I can remember engineers trying to solve a problem with an a320 apu auto-shutting down.
They took oil samples for 3 days and nailed it by examining the 'filings'!

As previously stated, those filings could be the answer to serious problems.

10th Oct 2009, 06:30
If there was enough debris accumulated in the filter element to trigger the deltaP sensor, then you have a serious issue. I'm sure your engine lube circuit also has magnetic chip detectors, but if they have not given an indication, then the debris source is non-magnetic and is not due to a gear or bearing failure. Chip detectors typically have a filter screen around them, so your mechanic should pull both the chip detectors and their filter screens to check for debris.

Since the cooler is downstream of the filter, and you apparently have cooler contamination due to contaminated oil being bypassed around the clogged filter element, then you also will have contamination of your engine's bearing oil jets and bearing chambers as well as your entire EMAD lube system. So the entire engine should be taken out of service, torn down, and inspected. Not just the oil heat exchanger and EMAD.

I've seen all types of non-magnetic debris end up in turbine engine lube systems and EMADs. Most of it originates at manufacture and assembly, and is sometimes composed of harmless substances like rag fluff, or other times more damaging debris such as core sand, machining chips or grinding wheel fragments. If this is EMAD debris, it circulates around in the EMAD lube system until enough collects on the filter to trigger the deltaP sensor. Or as in your case, it clogs the filter enough to pop the bypass valve.

Turbine engine lube systems are designed with enough filters and safeguards to prevent any catastrophic failures. That's why you're still around to ask this question.

Good luck.