History of Flight
On November 13, 2009, at 1651 central standard time, a Piper PA-46-310P, registration N667PC, experienced a total loss of engine power while descending from cruise flight. The pilot executed a forced landing in a corn field near Elk Mound, Wisconsin. The airplane sustained minor damage, and the pilot was not injured. The flight was conducted under 14 CFR Part 91 as a personal flight on an instrument flight rules flight plan. The flight departed Fargo, North Dakota, at 1530 and was en route to Eau Claire, Wisconsin.
The pilot reported that before departure from Fargo, the engine oil level was 5.5 quarts with the engine hot. During cruise at 4,000 feet, oil pressure and engine temperature indications were normal. The pilot observed a drop in oil pressure followed by a popping sound from the engine, after which the engine lost all power. The pilot then performed a forced landing.
Aircraft Information
The 1984 model Piper PA-46-310P, serial number 46-8508001, was registered to the pilot on August 11, 2004. Originally manufactured with a Teledyne Continental Motors TSIO-520-BE1G engine, the engine was replaced on September 30, 2005, with a Teledyne Continental Motors TSIO-550-C1B (serial number 814574-R) under a supplemental type certificate. At the time of engine installation, the airplane total time was 3,583.3 hours.
Engine logbook entries indicate that on November 22, 2006, at an airplane total time of 3,987.0 hours, the number 6 cylinder was removed to repair an exhaust leak; the connecting rod was reinstalled with new bolts and nuts after a bushing replacement. On April 7, 2009, at 4,337.0 hours, the number 6 cylinder was removed due to low compression (10/80) and replaced with an overhauled cylinder. The connecting rod was not removed during this maintenance. The last oil change was performed at this time, 107.6 hours before the incident. An oil analysis on April 7, 2009, showed abnormal concentrations of wear metals, with a recommendation to check the oil filter for chips and resample within 15-20 hours.
Wreckage and Engine Examination
Visual examination of the engine revealed holes in the crankcase above the number 5 and number 6 cylinder assemblies. The oil filter element contained metal debris. No external oil leaks were noted except from the crankcase holes.
Disassembly of the engine revealed that pistons 1 through 5 were undamaged with their pins intact. The number 6 piston was fractured around its circumference at the second ring land and through the piston pin hole, with a granular fracture surface. Connecting rods 1, 2, and 3 were attached to their pistons. The number 4 connecting rod was fractured through its base and cap, with its bolts and nuts fractured. The number 5 connecting rod was separated at its midpoint and at the base of the rod arm, with its cap completely separated. The number 6 connecting rod cap was separated from the rod.
The oil pump drive was intact; the pump cavity walls exhibited scoring, but the gear teeth were intact. The oil pressure relief valve and seat were unobstructed. Oil passages were intact and unobstructed. The crankshaft was intact with no evidence of cracks.
Metallurgical Examination
Metallurgical examination focused on the connecting rods and crankshaft. The number 4 connecting rod displayed a fatigue crack with ratchet marks indicative of multiple origins on the exterior surface of one arm. The crack extended through the arm and terminated at the inside surface, where a shear lip was present. Other fracture surfaces were obliterated by mechanical damage. The number 5 connecting rod fracture surfaces were also obliterated. The number 6 connecting rod arms remained attached to the body; its cap was split into two pieces, with one cap bolt fractured consistent with shear. The number 6 connecting rod bearing showed minor wear with no evidence of black or blue tint.
The crankshaft was intact with no cracks. The number 6 rod journal was smooth with minor blue tint and no dents. The number 5 rod journal exhibited severe mechanical damage, dents, and a black tint. Journals 1 through 3 were smooth with no discoloration. All oil holes were unobstructed; a wire inserted through them showed no resistance and no metal fragments.