Accident Details
On May 25, 2012, about 1536 central daylight time, a Mooney M20J single-engine airplane, registration N2159D, experienced a total loss of engine power during cruise flight. The pilot attempted a landing at Ozark Franklin County Airport (7M5), Ozark, Arkansas. The pilot sustained minor injuries; a passenger was not injured. The airplane sustained substantial damage to the fuselage and both wings.
Pilot Actions
The pilot reported noticing a change in engine sound while in cruise. Engine gauges were within green arcs, then RPM dropped and a bang or pop was heard. The propeller stopped rotating. Air traffic control provided vectors to 7M5. The pilot circled the airport 4 or 5 times and set up for landing. During the approach, the airplane was high and overshot the runway. The pilot turned to avoid buildings and attempted a landing on a nearby road, but the left wing impacted the ground.
Maintenance History
According to maintenance records, the most recent annual inspection was completed on May 11, 2012. The engine had 258.5 hours since its most recent overhaul. The propeller governor had been removed and reinstalled for overhaul; an oil change and ground run were accomplished with satisfactory results.
Engine Examination
The airplane was powered by a Lycoming IO-360-A3B6D engine. Initial examination revealed oil streaking on the fuselage from the cowl. No oil was present in the engine; the aft connecting rod protruded from a hole in the crankcase. The propeller governor installation appeared correct, and no leaks from the governor pad were observed. The crankcase oil drain plug was secured with safety wire, and no leaks were found. The source of the oil leak could not be identified.
During disassembly, the No. 4 connecting rod cap was missing, and the crankshaft end was deformed and discolored. Pieces of the cap were found in the crankcase debris. Very little torque was required to remove intact connecting rod cap bolts, particularly on the No. 3 rod. The No. 1 rod showed no heat discoloration; Nos. 2, 3, and 4 showed varying heat discoloration, with No. 4 most affected.
Examination in the NTSB Materials Laboratory revealed fracture surfaces on the No. 4 rod cap pieces were obliterated. A trapped bolt fragment showed features consistent with overstress failure. Heat tinting was observed on Nos. 3 and 4 rods and cap pieces. The No. 3 rod cap had impact marks; its bearing showed heat damage and extrusion. Pits, delamination, and smeared material with copper-lead coloration were observed. One No. 1 connecting rod bolt exhibited necking deformation. Bolts from cylinders 1-3 were measured; one No. 2 bolt was slightly undersized, and remaining bolts were longer and smaller in diameter than specifications.