NTSB Identification: ERA09IA009
14 CFR Part 91: General Aviation
Incident occurred Sunday, October 05, 2008 in Lakeland, FL
Probable Cause Approval Date: 03/23/2010
Aircraft: CIRRUS DESIGN CORP SR22, registration: N101CD
Injuries: 1 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
While approaching the destination airport, the pilot attempted to extend the flaps to the 50-precent position. After moving the selector, the pilot heard a "bang" and the airplane rolled right. The pilot maintained control of the airplane, and after landing noted that the flaps were extended asymmetrically. Post-incident examination of the flap system revealed that flap actuator rod end was bent 90 degrees, and broken. No other anomalies of the flap system were found. The condition of the flap actuator rod end suggested that the rod end was bent initially while retracting the flaps, an action associated with extension of the flap actuator. This resulted in cracks forming at the thread roots along the outer bend. Subsequent attempts to extend the flaps placed the rod end under a reverse bending moment that acted to straighten the rod end. The manufacturer's assessment of the situation in a service bulletin concluded that the flaps could have been retracted beyond the full up position, possibly due to a sensor failure, initially bending the rod end. During a subsequent deployment, during the incident flight, the flaps over-deployed and allowed the flap actuator linkages to over-center. The rod end subsequently failed, and allowed the asymmetric flap condition.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: A failure of the flap actuator rod end due to low stress, high cycle fatigue, and subsequent overstress failure. Full narrative available
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