CESSNA 182 — Littleton, NC

What happened

During a personal cross-country flight, the commercial pilot reported to air traffic control that he had a mechanical issue and wanted to return to an airport near his departure airport. The controller acknowledged the pilot's request and cleared him direct to that airport. About 5 minutes later, he reported that he needed to land and requested the nearest airport. The controller cleared the airplane direct to the nearest airport. Shortly thereafter, the pilot reported that he lost engine power and would have to land immediately. During the landing in a field, the nosewheel embedded in soft ground, and the airplane came to rest inverted.

An external examination of the engine revealed that four of the pistons had seized due to bearing and connecting rod damage. Metallurgical examination of the engine case halves revealed a gray-colored sealant on the crankcase main journal bearing saddle bosses mating surfaces. A bead of sealant was also noted on the edges of the mating surfaces both on the interior and exterior edges. The engine likely failed due to insufficient oil supply to the bearings for three of the connecting rods and the rotation of the fourth bearing. It is likely that beads of sealant were squeezed out of the mating faces of the crankcase and that these beads of sealant broke off and contaminated the oil supply, thereby reducing the oil flow. In addition, as the sealant on the saddle faces was squeezed out over time, the crush load could have been reduced, which would have affected the clearances between the bearings and the journals, leading to reduced oil pressure to the connecting rod bearings and increased risk of main bearing shifting and spinning. Thus, the use of sealant likely contributed to the bearing lubrication issue.

A review of the maintenance logbooks revealed that the engine had been overhauled and modified about 4 years (and 300 hours of operation) before the accident. Overhaul and modification instructions and manuals stated that the engine should be overhauled in accordance with the original equipment manufacturer's manuals and service bulletins, which indicated that no sealant should be applied on the main journal bearing saddle bosses.

None of the prescription medications the pilot had reported to the Federal Aviation Administration were impairing. Given that there was no indication of pilot impairment in his exchanges with the controllers, it is unlikely that the pilot's cardiac disease played a role in the accident. Indomethacin was found only in the pilot's urine, not in other body tissues; thus, it could not have directly caused systemic symptoms.

The diphenhydramine measured in the pilot's aortic blood (0.26 ug/ml) was well above the therapeutic range of 0.0250 to 0.1120 ug/ml. Although diphenhydramine undergoes postmortem redistribution, the level suggests that the pilot had therapeutic amounts in his system at the time of the crash; thus, it is likely the pilot was impaired to some extent by the drug's effects. However, the available evidence indicates that the pilot's behavior and decision-making during the accident sequence were appropriate for a pilot with his skill level and knowledge. Therefore, the effects of diphenhydramine likely did not contribute to the accident.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.