View Full Version : Crankshaft corrosion
currawong
15th Oct 2003, 16:55
Crankshaft corrosion.
Anyone had a run in with this?
Spanners tracking oil leak found some under the forward seal, causing a leak.
Causes? Prevention? Or is it just slackness on the part of the engine rebuilder?
Cheers
And the specific engine type was....?
Yes, a few have had a problem with this, mostly Lycoming.
ferrydude
16th Oct 2003, 00:39
This is not the overhaulers problem. It is most common in Lyc engines with hollow cranks and fixed pitch props. Sludge gets in there and cannot get out because there is no flowpath as there is with a constant speed prop. The sludge is corrosive, (acidic). Can be prevented by either removing the end plug periodically and cleaning the crank bore, or by coating the bore with an epoxy sealant
I thought this was a repeat mandatory AD for most Lycoming recip engines! 100 hrs insp for corrosion and cracks using eddy current or other non surface NDT (i.e. not dye pen)
Could be wrong or got my wires crossed here as it was being done while I was looking at an avionics snag on the same a/c. My normal a/c are alot bigger than 2-6 seaters.
A look at the FAA web site will soon give you an answer.
ferrydude
16th Oct 2003, 05:57
naaahh, only applies to 320 and 360 series with fixed pitch props and other than solid cranks. visual inspection, then FPI if on aircraft and Magnaflux at overhaul. Reinspection could go up to 10 years to the next depending on the results of the intial insp.
currawong
16th Oct 2003, 06:47
Thanks for replies fellas.
Engine is IO-520D
Corrosion is on outside of crank, underneath forward crankcase seal. This corrosion has been wearing away said seal causing oil leak at front of engine. This then hits the prop and gets flung everywhere. So it is not exposed to elements, not visible untill seal is removed.
Word is removal of corrosion may take crank out of limits....
Non removal may lead to failure, or at least flying around in a cloud of oil.
Engine still in warranty, so not an age problem.
Cheers
ferrydude
16th Oct 2003, 06:52
aha, a new twist. You mentioned that it could be the fault of the rebuilder. This implies that age may be a factor, as well as the environment where it "lives" Near the beach? near any body of saltwater? Do any lowflying in these areas?
currawong
16th Oct 2003, 17:58
Thanks ferrydude.
Engine is rebuilt to manufacturers specs.
Age I do not know, but new to us as exchanged for time-ex unit. Less than half TBO.
Could be age or environment, but spanners are saying by the look of it there should have been some indication of it at overhaul. (fairly well established considering type of metal etc)
Wondering what the rest of it looks like, the part we cannot see, based on the part we can.
Second opinion/previous experiences welcome.
Cheers
ferrydude
16th Oct 2003, 18:26
I have not heard of this being an issue, I have quite a bit of experience with the 520 series. I do know that the TCM cranks are not quite as robust as the Lycs are. Many cases of fracture and seperation are out there, particularly with the 520 series. Have you consulted TCM tech reps? I have had excellent help from them in the past