Accident Overview
On April 9, 2012, at approximately 1325 eastern daylight time, a Cessna 172S, registration N375LP, was substantially damaged during a forced landing following a total loss of engine power near Daytona Beach, Florida. The flight instructor and commercial-rated student pilot were not injured. The airplane was operated by Air America Flight Center LLC under Part 91 as an instructional flight. Visual meteorological conditions prevailed, and no flight plan was filed. The local flight originated from Daytona Beach International Airport (DAB) at 1310.
Sequence of Events
According to the flight instructor, after reaching a cruise altitude of 3,000 feet mean sea level, the engine began to run rough and several loud noises were heard. The instructor assumed control from the student and assessed the situation. The engine then lost all power, with zero oil pressure and rpm. Oil was visible on the windscreen. After securing the engine, the CFI set up for a forced landing in a nearby field. The landing was uneventful until the landing gear contacted a ditch, causing the airplane to nose over.
Damage and Examination
The flight instructor reported substantial damage to the wings, fuselage, and vertical stabilizer. An FAA inspector performed a cursory examination and noted that the engine case was ruptured and the camshaft was partially exposed. The engine was secured for later disassembly.
On April 12, 2012, the FAA inspector conducted a disassembly and inspection. A hole was evident in the lower engine case due to internal damage. Internal parts appeared well lubricated with no evidence of oil starvation. The camshaft was partially pushed through the case and fractured. The inspector suspected a failure of the number four piston, which was removed for further NTSB examination.
Engine and Maintenance History
The engine had accumulated approximately 222.5 flight hours since its last overhaul and 2,965.1 hours since new. It was inspected 66.6 hours prior to the accident. Maintenance records indicated that the airplane was involved in a propeller strike on February 10, 2012, with a subsequent inspection.
NTSB Materials Laboratory Findings
Staff from the NTSB Materials Laboratory examined the number four cylinder, piston fragments, and other engine fragments from the Lycoming IO-360-L2A engine. Most adjacent components showed signs of buffeting and impact. The lower bore of the connecting rod was collapsed inward. The oil seal gasket appeared serviceable. The cylinder bore exhibited rust-colored oxidation, consistent with post-failure corrosion.
The piston crown was fractured from the connecting rod and embedded off-center in the cylinder bore. The crown had multiple fractures, with two primary fracture surfaces perpendicular to the crown face. Both surfaces displayed smearing from post-fracture contact. Undamaged areas appeared dull and fibrous, with microscopic facets. River patterns and tear ridges indicated cracking direction from the rod side to the crown face.
Scanning electron microscopy (SEM) revealed dimple rupture on isolated areas, indicative of overstress failure. Dimple morphology suggested tensile, shear, and mixed directional failure. The fracture surface also contained second phases high in silicon that had fractured by cleavage, typical of high-silicon aluminum castings with lower ductility than forgings. Energy dispersive X-ray spectroscopy confirmed the piston material as high-silicon aluminum casting, with lead-based particles consistent with aviation fuel additives. No preexisting mechanical damage (such as fatigue) or corrosion was found on the fracture surfaces.