Premature Camshaft / Cam Follower failure

Thanks, achimha

Just in case anybody is interested: Below are two sample results sheets. Top one is from the company in Germany which provides some more data points (no idea how relevant those are), bottom one is from AVlab in the US.

The lifter pitting in the photos is the same as that you see on older solid lifter (road) engines, particularly when running modern oils with emissions related additive packages. On Moto Guzzi big block twins this became something of a crisis a few years ago, but seems to have improved – at least there’s less talk on the web about it now. Oddly enough, every one of those (Guzzi) engines I’ve ever taken apart, since the late 80’s, has had some pitted lifters and it makes you wonder how the failure mechanism works… They keep running that way and with a motorcycle engine few people cut apart the oil filter to find the metal. I think the first time it gets noticed might be after a very long period of running, when the engine is apart for other reasons.

Maybe the non-aircraft experience will be of some interest.

There are European / UK companies that do oil analysis.

See my reports / comparisons of avlab / blackstone / intertech here for example.

I used Avlab for years and bought something like 100 of their prepaid kits, of which most were sold to other pilots (mostly below cost ). They used to be incredibly cheap years ago (£6.50) but that was years ago. I would not use them anymore because their data is simply unreliable – as was revealed when the same oil was sent to two other companies (Blackstone USA and Intertech UK) – read the above linked report.

I guess Avlab is OK if you just use them as a trend and I am sure that if your metals go right through the roof then they will indicate that reliably enough. So it is not a million miles different from PSA testing, though there have been big recent advances there too, with hi-res MRI, which the medical establishment mostly doesn’t accept

Blackstone is about $20 (from memory) plus airmail to the USA, and Intertech is £25 plus UK postage. These two produce very similar data and I would be happy to use either. As you will see in my report, Blackstone did once mix up my oil with somebody else’s… that was proved only because I use Camguard which leaves about 100ppm of calcium as a marker (clever!).

I cannot see any point in paying amounts like 50 quid, given that Intertech are formerly the UK Ministry of Defence and have pretty good QA procedures and their data is so close to Blackstone who are the #1 firm in the USA. One could argue that Blackstone have more aircraft engine experience than Intertech, due to the vastly bigger US GA pool.

It’s a non-functioning industry without competition unfortunately.

We can thank low volumes and mainly certification for that.

Replacement, especially when talking mass-produced automotive engine cores, may just be a more secure option.

The question is for how long. Automotive engines will move on, aviation diesel conversions will probably stay at the current technological level – just like the 1950s automotive engine conversions from Lycontinental.

It takes time to see if roller lifters have own problems but in modern carengines these are reliable.

That remains to be seen. The flat tappets were taken from a 1950s car engine where they apparently worked reliably too.

This is of no help to you now but if oil analysis was being done, you may have got a much earlier warning.

I wish that was true. I’ve seen the oil report of an engine making good heaps of metal – the lab comment read something like “slightly elevated, but no cause for immediate concern”.

I wish that was true. I’ve seen the oil report of an engine making good heaps of metal – the lab comment read something like “slightly elevated, but no cause for immediate concern”.

That’s also true. Whether oil analysis will give a warning of this kind of thing depends on what triggered it.

If it was triggered by corrosion, you will see a huge rise in iron, and a corresponding huge rise in the other metals especially the softer ones like copper which wear easily. I had one incident where the alternate air door was not closing properly (after an Annual service) and this gave a big rise in copper – presumably due to the dirt being ingested which also showed up. Not sure I would like to repeat this post-Calvi, with all the sh*t which every plane taxiing there throws into the air filter…

If it was triggered by surface disintegration (bad metal, or lack of lube) then you might see nothing in the oil analysis. You should see it in the oil filter though – if you religiously cut it open.

There was a famous 4x fatal PA28 crash on the Isle of Wight a few years ago, and they found something like 20-30% of the valve lift gone, due to a trashed camshaft. I sent the accident report (with details of the cam damage) to two respected US engine shops and both thought it was very possible that nothing at all would show up in oil analysis. However given its obvious “maintenance history” this aircraft would have been doing well to see an oil change, never mind somebody cutting open the oil filter (which obviously never happened), let alone somebody doing oil analysis.

The Australians are pretty clear on that. Probably you have a set of 15B26064 tappets.

Link

Had a brief moment of panic as my engine was overhauled in 2012….but Late 2012 not late 2009 – Mid 2012….and my records show the 15B26062 tap pets were used….phew

I also use Camguard which recommendation #2 alludes to

Any views on ‘ground running’ an engine say once a week that may not otherwise fly.

Con; you’ll just scrape off any oil left on the cam and the oil won’t get warm enough to boil off the water

Understand that Club Aircraft that fly regularly normally make TBO with out a problem !!!

This looks like an unfounded rumour to me… One of the clubs I’m member of recently bought 4 new C172SP – and engine problems on one started after maybe 150 hours.