NTSB Identification: ATL03LA059.
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Accident occurred Friday, March 07, 2003 in Gordo, AL
Probable Cause Approval Date: 06/28/2006
Aircraft: Aeronca 7AC, registration: N1648E
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.
During cruise flight a "bump" was felt under the pilot's seat, then the airplane pitched up erratically and became difficult to control. The pilot selected an open field and executed an emergency landing. The airplane came to rest in a pond. The pilot reported that the crankshaft sheared behind the propeller flange and in front of the crankcase. Examination of the airplane on site revealed that one of the propeller blades separated at the flange, there was substantial damage to the nose bowl cowling due to the airplane nosing over into the pond. The firewall was bent slightly rearward at the base and there was also water damage to the wing spar. Further examination of the partial crankshaft recovered, revealed that the separation had occurred between the oil slinger and the propeller mounting flanges leaving a fracture face. The fracture face displayed arced crack arrest marks, consistent with fatigue propagation. The arcing of the crack arrest marks indicated that the fatigue origin was located further forward, towards the propeller-mounting flange on the unrecovered portion of the crankshaft.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: Fatigue failure of the crankshaft. Full narrative available
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