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Aircraft oil sampling - High wear metals
When your aircraft oil sample comes back from the lab and shows high wear metals it is important to consider the
three possible reasons for the high wear metals:
1. Component or lubricant failure is causing metal-to-metal contact wear
(two body wear).
2. Wear is being created by dirt (abrasive) in the airplane engine (three body
wear). See Dirt, Silica and Silicon
3. Corrosion of metal
For example, if you haven't flown your airplane in a while the aircraft
oil sampling results may show high iron. This could be caused by slight
corrosion from the steel cylinder barrels, in which case the iron content in the
oil sample should spike and then go down assuming you fly more often. Lets take
the case where you fly often so rust is not a suspect. You notice that the
amount of silicon is high. Silicon is from dirt and the iron could be produced
by abrasion; However, if Silicon levels are low and you still have high iron
then it is more suspect that you have metal-to-metal contact wear (two body
wear) that is more indicative of lubricant and possible part failure.
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