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Thursday, July 18, 2013

Newest project

As part of the normal maintenance routine on an aircraft, when you change your oil you cut open the filter and inspect the paper pleats looking for pieces of your engine and that's why this Mooney is in our shop today.  When the filter was opened a significant amount of steel particles was found in the filter.  The owners sent the plane down to us for inspection and a recommendation.
 I removed the cylinders on one side to get a good look inside the engine and this is what I saw...
 I know it is a little hard to tell but the cam and tappet body on the the left has some pitting and erosion happening.  The left tappet and cam should look shiny and smooth like the right tappet and cam.
 We contacted the owner and advised him that the cam and tappet were degrading and that the engine would need to be overhauled or repaired before it was safe to fly again.  He chose overhaul since the planes engine was almost out of time anyways.
 Here is a picture of the same tappet after the engine was removed and the case split.  Notice that the right tappet has an excessively worn spot as well, a divot/dent.
And here is a shot looking down the camshaft.  Notice, the near cam is taller and pointier than the cam that is two back and in the same position.  That is because the the tappet has slowly eaten away at the cam.  The main problem with this condition other than loose metal floating around your engine is that the cams job is to open and close the intake and exhaust valves on the cylinders.  When the cam is worn away like this it is not able to keep the valve open as long as it is needed to and depending on the position of the cam whether intake or exhaust it robs that cylinder of power.  As the cam continues to erode eventually the cam will be worn completely way and the cylinder will be useless or worse.

Thanks for checking in, Josh

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