Cessna R172 N758DK accident near Cresskill, New Jersey

Probable cause

Maintenance personnel’s failure to apply proper torque to the cylinder flange nuts and through bolts during installation of the engine cylinders, which resulted in the loosening of the components, loss of lubrication, failure of the crankshaft, and the subsequent total loss of engine power.

NTSB analysis

The private pilot reported that, while the public aircraft flight was in cruise flight about 2,000 ft mean sea level, the airplane's engine stopped producing power. During the subsequent descent, the pilot chose a large open area of several athletic fields for the forced landing. As the airplane approached the fields, the pilot observed that they were in use and that only a small space was available for landing due to people on the ground. The airplane subsequently landed hard and was destroyed during the impact.

Examination of the engine maintenance records revealed that the Nos. 3 and 4 cylinders had been removed and reinstalled 231 hours before the accident. The cylinder flange nuts and through bolts were checked for security and breakaway torque, and several were found below factory specification. Disassembly of the engine revealed metal fragments and bearing material in the oil sump. Disassembly of the crankcase revealed that it was fractured and that the Nos. 1 and 2 main bearings and bearing journals had damage consistent with a loss of lubrication, high heat, and fatigue. It is likely that maintenance personnel did not apply sufficient torque to the cylinder flange nuts and through bolts during the installation of the engine cylinders.

Text from the NTSB. Open the NTSB docket for ERA15LA338 for the full record.