NTSB Identification: WPR09CA091
14 CFR Part 91: General Aviation
Accident occurred Sunday, January 18, 2009 in Santa Ynez, CA
Probable Cause Approval Date: 04/15/2009
Aircraft: SIEMER JAMES H EARTHSTAR, registration: N532JS
Injuries: 1 Uninjured.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

According to the sport pilot, during cruise flight in his experimental light sport airplane he noted that the two-cylinder engine's cylinder head and exhaust gas temperature gauges decreased in temperature. Thereafter, the number 1 cylinder (rear) stopped producing power, and engine power was partially lost. The pilot made a forced landing on upsloping, rough terrain. During landing, the airplane's forward fuselage buckled. The pilot said that examination of the engine revealed that the spark plug had come out of the engine's rear cylinder head. The pilot had changed the spark plugs about 2.5 hours prior to the mishap.

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

A partial loss of engine power due to the rear cylinder's spark plug coming out of the cylinder head.

Full narrative available

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