Metal in the oil filter

Yes, you read the title right.

In August, shortly after the return from the Green Mountain Aerobatic Contest in Springfield Vermont, I made an oil change since my oil was 4 months old (per Lycoming Service Bulletin No. 480). The engine total time since new was a little more than 500 hours. The oil had 25 hours on it and the oil filter 40 hours.

I have a B&C spin-on filter adapter that allows me to use a 48108 paper filter. I like it since it provides better filtering and allows to change oil every 50 hours instead of 25 hours when using a screen filter (especially useful in summer when flying a lot).

In order to inspect my old filter, I used the "blue rag" technique recommended by this EAA video. When cutting the filter open, I didn't see any big particles with naked eye. However, when I collected all the content of the filter together, I found about 1/8th teaspoon of ferrous metal powder:

Following this finding, I wanted to know what are the typical recommendations for this quantity of metal. Lycoming Service Instruction 1492 has info on recommended actions when finding metal in the oil filter. When reading this SI, I concluded category 8 d. was the closest to my situation:

"As in step b., but larger amount, such as 45-60 small pieces – change oil filter and clean suction
screen, drain oil, and refill. Run engine on ground for 20-30 minutes. Inspect oil filter suction
screen. If clean, fly aircraft for 1 to 2 hours and again inspect oil filter/suction screen. If clean,
inspect oil filter/suction screen after 10 hours of engine operation."

The step b. in question mentions:

"10 to 20 small (1/16 inch diameter or less) pieces of shiny flake-like, nonmagnetic, or 10 or
fewer short hair-like pieces of magnetic material"

The particles were all magnetic and way smaller than 1/16". Stricly speaking, they were not "hair like", but I didn't find a description in this service instruction that fitted better my situation. The generic recommendation from Lycoming is therefore to continue flying "on condition".

The following factors specific to my situation were also worth consideration:

1. The engine was manufactured in 1979 and has never been opened since new. If it had flown consistently 1 hour every month since new, corrosion wouldn't be too much of a worry, but obviously it is not the case. Lycoming cams and lifters are know to be subject to corrosion if not operating for extended periods of time.
2. The situation will not improve by itself. It can only get worse. More particles like this means more chances of getting into other parts of the engine and making more damage.
3. This engine is in a Pitts. Lycoming's recommendation applies also on a Cessna 152, but I think nobody would argue that the severity level of an engine failure on a Pitts is more hazardous.

...so in light of all the above factors and recommendations...

Yes, I know. The bullet is getting pretty chewed up, but here I am. Season is over after only 15 hours of flying : ( It was a very intense 15h though and I enjoyed every second of it. I'm already anxious to put a nice, clean engine back in and go fly next season.

Thanks to Mathieu who helped in crating up the engine. Big thanks also to François Marquis, Kevin Horton, Mike Busch and JP Ouellette who all were of great help in gathering the pieces of the puzzle to make my decision.

Here's a shot of the engine just before getting shipped to Aerorecip in Winnipeg:

Next post will be on the findings from the shop... Stay tuned!