Aircraft Accident Investigation Report

37 The engine does not show to have been updated to (-T) mod configuration per Lycoming Service Instruction 1406. The oil pressure relief valve had a hexagonal nut and two washers installed in lieu of the specified washers as stated in the Illustrated Parts Catalog (IPC) for spring tension adjustment as seen in Figure 43. Figure 43 Oil Pressure Relief Valve The intake and exhaust were found to be open and free, there were no obstructions. SUMMARY The engine examination revealed no evidence of pre-impact catastrophic mechanical malfunction or fire. Mechanical continuity was established during the hand rotation of the crankshaft and thumb compression check of the cylinders. The cylinder(s) bore scope examination showed light rust on the No. 2 cylinder walls, remaining cylinders were unremarkable. The spark plug electrodes remained mechanically undamaged and exhibited coloration consistent with normal operation. The internal timing of the engine was found to be off by 1 tooth when the timing mark of the crankshaft was properly indexed to the parting face of the engine case. The No. 2 engine cylinder intake valve was incorrect as noted by its short length when compared to the three remaining intake valves; this suspect valve has a Lycoming part number, just not for this engine model or type certificate. The No. 2 engine cylinder intake valve also did not have any shims under the rocker arms. The camshaft showed signs of wear on lobes ranging from worn to extremely worn conditions with heavy pitting and corrosion exhibited. The No. 3 engine cylinder intake and exhaust tappets and the No. 4 engine cylinder intake tappet showed heavy wear, pitting and spalling on the faces and edges of the tappets. 1.16.2 Aviation Gasoline (AVGAS) Analysis A sample of AVGAS was taken from the batch of fuel which was purchased and pumped in the aircraft (N101KA) from the fuel farm at Tinson Pen Aerodrome the day before the