It was a tough year for the mighty TwinBo. On dropping it off for annual, and after bragging to my buddy Martin that my annuals have been so reasonable the last 5 years in a row and my squawk list was short, they found some bits of copper in the left engine oil screen. Deep inspection of the engine revealed no anomalies... compression good, borescope clean, valves seating properly with no chips. Engine has 700 hrs SMOH. After some calls to Lycoming and Columbia it was advised for me to run it another 10 hours and check again. I ran it about 5 hrs and it ran perfectly, then checked the screen again and it was clean. Alls well that ends well right? Well it just didn't sit right with me. In the back of my mind I just felt like if something inside broke it wasn't going to fix itself. When something comes apart inside my engine, I want to know what it is and fix it. So I took the plane to West Air aircraft engines at Livermore and asked them to figure it out. They took off all the jugs and found the culprit. Apparently the connecting rod wrist pin caps were likely not originally installed correctly and one of them was not rotating and was badly cracked.
Another one was cracked and two other ones had minor chipping too. Simple fix right, just replace the caps? Well the reason it cracked is that since it couldn't float freely it got hot and also melted part of the piston. I was relieved to have found the source though, and it was advised I should replace all the wrist pins and wrist pin caps and pistons, new rings and hone the jugs, check all the valves and valve stems and push rods. Basically a light top overhaul. During this process they also discovered that the connecting rod arms had the part number scratched onto them. That's probably no big deal safety wise but it's not allowed by Lycoming, so I also needed to replace all the connecting rods. So all the cylinders on the left engine got new pistons and rings, honed the cylinders, new connecting rods and bushings.
All this saga started in August and I just picked it up yesterday. I test flew it by flying it over the airport for half an hour with my buddy Aaron in the plane with his eyes glued to the JPI. All ran very well with low CHTs (it was cold by CA standards yesterday) except a bad probe on the #1 EGT. The shop replaced the probe on the house since he felt bad I just had to write a 24k check! Then I flew home. So the plane is finally back in the hangar. It's got mineral oil in it so I'll need to break in these jugs by flying it at 75% power over the next 10 to 15 hrs. I'm looking forward to putting more than 20 hrs on it this year!
