Lycoming; IO360-A3B6D; Failure of Cylinder Attach Studs and Bolts; ATA 8530

A pilot reported his engine was beginning to run rough. Engine monitor readings indicated the number two cylinder had failed, prompting a safe landing at Reno. The subsequent maintenance investigation found both upper through-bolts and both upper cylinder attach studs for the number two cylinder had failed at the cylinder flange. Additionally, the lower aft through-bolt for the number one cylinder was found to have failed at its flange.

The writer states: “The engine had a total time of (4382.9) hours and had been overhauled 1540.9 hours previously....” All four cylinders had been replaced at 4,177.7 hours, giving 205.2 hours actual part time. “Failure of the studs and bolts appears to be consistent with either under-torque or over-torque of the nuts at installation.”

(The submitter gives 4,832.9--a common transposition error, if the math is going to work.)

Part Total Time: 205.2 hours.