Piper PA32-300 N2242Z accident near Branford, Connecticut

Probable cause

Maintenance personnel's improper installation and inspection of the crankshaft gear bolt during major overhaul, which resulted in the crankshaft gear disengaging from the accessory gears which led to a total loss of engine power.

NTSB analysis

The pilot stated that shortly after takeoff the engine made a popping noise with a noticeable loss of engine thrust. The rpm gauge indicated “0” but the propeller continued to rotate. The pilot declared a MAYDAY and made a forced landing in the ocean. Postaccident examination of the engine revealed that the crankshaft gear bolt was about 1/8th inch out from being seated on the crankshaft gear. The crankshaft gear bolt head was rounded, and the bottom threads of the bolt were damaged. The crankshaft gear was removed, and the alignment dowel was found sheared. Four teeth were also sheared from the oil adapter idler gear. Metallurgical examination of the fractured components determined they had fractured from shear overstress.

Per the engine maintenance log, at the last annual inspection (about 6 months prior to the accident), the engine had had accrued about 650 hours since it was overhauled. There were no entries in the maintenance records to indicate the crankshaft bolt had been removed, inspected, or modified since the engine had been overhauled. Based on the available information it is likely that when the engine was overhauled, the crankshaft gear bolt was not properly seated against the crankshaft gear, which resulted in the crankshaft gear eventually disengaging from the accessory gears leading to a total loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA25LA215 for the full record.