Cessna 170B N8339A accident near Mahwah, New Jersey

Probable cause

A loss of engine power due to the failure of the No. 1 cylinder thru bolt hold down nuts due to corrosion.

NTSB analysis

During a cross-country flight, the airplane’s engine began to vibrate heavily, lost all power, and the pilot executed an emergency landing in a field. During the landing roll, the airplane impacted a hill, and sustained substantial damage. On a previous flight, the pilot recalled a vague vibration while en route. A mechanic was unable to identify the source of the vibration, and a "no defects noted" statement was entered into the logbook after various component checks. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the No.1 cylinder revealed that two thru bolt nuts were loose. Two of the other bolts were sheered off, and one was missing. The threads on the thru bolt, with the missing nut, were rusted.

Text from the NTSB. Open the NTSB docket for ERA09LA409 for the full record.