Piper PA 28R-201T N44903 accident near Atmore, Alabama

Probable cause

A total loss of engine power due to oil starvation caused by insufficiently torqued cylinder through bolt nuts, which caused bearings to shift and led to the subsequent failure of the No. 3 connecting rod.

NTSB analysis

The private pilot and the passenger departed on a cross-country flight. The pilot stated that the airplane was at an altitude of 4,500 ft mean sea level when the engine lost oil pressure, followed by a total loss of engine power. The pilot landed the airplane on a two-lane country road. During the landing roll, the airplane's right wing struck mailboxes, which caused substantial damage to the right wing. Examination of the engine revealed the torque values for the No. 2 cylinder upper through bolt nuts, both No. 3 cylinder through bolt nuts, and the No. 5 cylinder through bolt nuts were below factory specifications for breakaway torque. Further examination revealed that the No. 3 connecting rod was separated from the crankshaft, the No. 2 main bearings had shifted, and there were signs of oil starvation. The likely insufficiently torqued nuts allowed the No. 2 bearings to shift and rotate, which resulted in oil starvation to the corresponding connecting rods and main bearings and ultimately led to the failure of the No. 3 connecting rod, ancillary damage to other internal components of the engine, and a total loss of engine power. Review of maintenance records revealed that the No 3. cylinder had been removed and reinstalled about 1 year before the accident. The engine's most recent annual inspection was completed about 9 months before the accident. There were no irregularities noted, and all airworthiness directives were complied with as noted by the mechanic. The investigation could not determine whether the loosening of the nut torque was due to improper installation or another unrelated issue.

Text from the NTSB. Open the NTSB docket for ERA15LA345 for the full record.