NTSB Identification: LAX06LA103.
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Accident occurred Monday, February 06, 2006 in Thermal, CA
Probable Cause Approval Date: 11/29/2007
Aircraft: Harwood Kenneth Lancair 360A, registration: N15KH
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The airplane collided with power lines during a forced landing following a loss of engine power. The pilot reported that while maneuvering at 2,000 feet the engine began losing power. The pilot decided to divert to a nearby airport to make the emergency landing. While en route to the alternate airport, the pilot observed a part of the engine departing through the cowling and the engine lost complete power. At that point he knew he was not going to make it to the airport and decided to make a forced landing on a highway. Examination of the engine showed that the number three cylinder separated from the crankcase at the mounting pad due to the separation of its mechanical attachments. Once the cylinder separated, the piston then became unsupported, which resulted in the subsequent separation of the connecting rod from the crankshaft journal. Severe fretting signatures were found on the cylinder flange and crankcase mounting pad. The threads on the top hold down studs were undamaged and indicated that these nuts became loose and backed off. The studs on the bottom of the cylinder were fractured in overload and separated at a level consistent with the upper surface of the cylinder mounting flange.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A loss of engine power caused by the separation of the number three cylinder due to the improper torque on the hold down nuts.

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