NTSB Identification: CHI05LA143.
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Accident occurred Wednesday, June 15, 2005 in Redford, MI
Probable Cause Approval Date: 03/28/2006
Aircraft: Thomas Zenith CH701, registration: N613DT
Injuries: 1 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 amateur-built airplane sustained substantial damage during a forced landing to a golf course after a loss of engine thrust. The pilot reported that he had flown for about one hour when he heard and felt a loud "bang" from the front of the engine. The engine lost power. He reported that he immediately declared a "MAYDAY" and executed a forced landing to a golf course. During the landing rollout he encountered rough terrain, and the airplane sustained substantial damage to the engine firewall. The pilot reported that all three wooden propeller blades had separated from the propeller hub. The inspection of the airplane revealed that the engine exhibited continuity and thumb compression. The two carburetors were found separated from their respective rubber couplers. Two of three propeller blades were recovered. The propeller hub and the two propeller blades were sent to the National Transportation Safety Board's Materials Laboratory for inspection. The inspection revealed that both blades appeared to be in good condition, with only a few small, shallow dents on the surface and no splintering or other damage to the blade tip or leading edge. The fracture of the wood of the three propeller blade root ends appeared to have fractured in shear stress. Calculations indicated that normal operation of the engine would produce a shear stress of 741 psi on the propeller blades. In the manufacturer's product testing, the blade retention had not failed until the application of about 2,200 psi. The number 1 propeller blade was not recovered which precluded its inspection for failure or defects.

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

The total loss of engine thrust was the result of the propeller blades overstress separation from the propeller hub for an undetermined reason. An additional cause was the unsuitable terrain encountered during the forced landing.

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