PPRuNe Forums

Go Back   PPRuNe Forums > Flight Deck Forums > Tech Log
Forgotten your Username/Password?

Tech Log The very best in practical technical discussion on the web


Reply
 
Thread Tools
Old 8th Oct 2009, 20:28   #1 (permalink)
 
Join Date: Jul 2003
Location: germany
Age: 42
Posts: 261
filings of metal in oil - how come?

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,
Cecco
Cecco is offline   Reply
Old 8th Oct 2009, 21:09   #2 (permalink)
 
Join Date: Aug 2008
Location: moving around
Age: 38
Posts: 98
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.
Wirelock is offline   Reply
Old 8th Oct 2009, 22:18   #3 (permalink)

 
Join Date: Jul 2006
Location: west of LTN
Posts: 194
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.
non iron is offline   Reply
Old 9th Oct 2009, 12:00   #4 (permalink)
 
Join Date: Oct 2006
Location: berkshire
Posts: 85
metal in filter

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.
mitzy69 is offline   Reply
Old 9th Oct 2009, 15:23   #5 (permalink)
 
Join Date: Feb 2005
Location: flyover country USA
Age: 72
Posts: 4,200
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!
barit1 is offline   Reply
Old 9th Oct 2009, 17:56   #6 (permalink)
 
Join Date: Oct 2004
Location: Near sheep!
Posts: 802
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.
WindSheer is offline   Reply
Old 10th Oct 2009, 05:30   #7 (permalink)
 
Join Date: Sep 2007
Location: USA
Posts: 236
Sounds like a serious problem.

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.
riff_raff
riff_raff is offline   Reply
Reply
 
 
 


Thread Tools


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT. The time now is 01:39.


vBulletin® v3.8.7, Copyright ©2000-2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
1996-2012 The Professional Pilots Rumour Network