NTSB Identification: CEN11LA429
14 CFR Part 91: General Aviation
Accident occurred Wednesday, June 29, 2011 in Oshkosh, WI
Probable Cause Approval Date: 02/23/2012
Aircraft: Keesler W8 Tailwind, registration: N56PK
Injuries: 1 Minor.

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 accident occurred during the initial flight testing of the experimental amateur-built airplane. The pilot reported that, during the initial climb, at an altitude of about 200 feet above the ground, the engine began to lose power. He notified the tower air traffic controller of his engine emergency and began a turn to remain clear of nearby buildings. The airplane encountered a ditch during the forced landing and the forward fuselage and firewall were substantially damaged.

The airframe had accumulated 4 hours since it was issued an airworthiness certificate and the engine had accumulated 5.7 hours since its last major overhaul. The pilot/builder replaced the carburetor, spark plugs, and a cylinder since the last engine overhaul. A postaccident examination of the engine revealed that both spark plugs for the No. 4 cylinder were loosely installed into the cylinder head. The upper spark plug for the No. 4 cylinder was not seated on its cylinder gasket. Several spark plugs were removed and exhibited features consistent with the engine operating at a rich carburetor mixture setting. Although a carburetor-icing probability chart indicated that there was a serious potential for carburetor ice accumulation while operating at a reduced engine power setting, the postaccident investigation could not determine if carburetor ice contributed to the loss of engine power.

The postaccident investigation was unable to determine the reason for the loss of engine power, which could have been a result of the incorrectly installed spark plugs on the No. 4 cylinder, an excessively rich carburetor mixture setting, an accumulation of carburetor ice before takeoff, or any combination of the aforementioned issues.

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

The loss of engine power during initial climb for undetermined reasons.

Full narrative available

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