Crankshaft failure for Cirrus

Aircraft: Cirrus SR22. Injuries: None. Location: Pickens, S.C. Aircraft damage: Substantial.

What reportedly happened: A few minutes after leveling the airplane at a cruise altitude of 9,000 feet MSL, the pilot felt the engine slightly vibrate and noticed the propeller rpm began to rise rapidly. The oil pressure warning light illuminated. After unsuccessfully troubleshooting the engine problems, he shut down the engine and declared an emergency.

An air traffic controller informed the pilot of an airport four miles from his location, and he turned the airplane toward that airport and prepared for an emergency landing. When he turned the airplane toward the base leg of the traffic pattern at 1,200 feet, he added one notch of flaps. He felt the handling characteristics of the airplane change and it began to feel “mushy.”

He then retracted the flaps, and the condition worsened. As the airplane descended through 1,000 feet, the pilot thought that he had “lost control of the airplane” and decided to activate the airframe emergency parachute. The parachute deployed, and, within seconds, the airplane settled into trees about two miles from the airport. The airplane remained suspended in the trees until emergency personnel arrived on scene and rescued the occupants.

After the accident, the presence of oil was noted on the underside of the airplane. After the airplane was recovered from the trees, examination of the oil dipstick revealed small pieces of metal in the engine oil.

Examination of the engine revealed that the crankshaft was fractured and that the crankcase exhibited varying degrees of fretting and lock-slot elongation on the main bearing supports, which is consistent with the application of insufficient torque on the cylinder through-bolts by maintenance personnel.

New cylinders had been installed on the engine 113 hours before the accident. Because the cylinders were loose, the oil supply at the No. 2 main journal was shut off and the crankshaft broke, which resulted in the subsequent loss of oil pressure to the engine.

Probable cause: A total loss of engine power due to the failure of the crankshaft, which resulted from the application of insufficient torque on the cylinder through-bolts by maintenance personnel.

NTSB Identification: ERA12LA473

This July 2012 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

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