NTSB Identification: IAD01LA107
14 CFR Part 91: General Aviation
Accident occurred Tuesday, September 25, 2001 in MEDINA, OH
Probable Cause Approval Date: 08/26/2003
Aircraft: Piper PA-32RT-300T, registration: N39945
Injuries: 1 Serious.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
After take-off, the pilot heard the engine "pop" followed by a loss of engine power, which resulted in a forced landing into trees. Examination of the engine revealed that a newly installed factory remanufactured single-drive dual magneto had separated from the engine. It had accumulated 17.9 hours at the time of the accident. Examination of the magneto and the installed clamping blocks revealed that the mounting flanges on both sides of the distributor housing exhibited fatigue beach marks. Examination of the mounting flanges also revealed that there were two sets of contact marks. The smaller more linear inboard set of marks matched the contour of the installed magneto clamping blocks when tilted slightly. These marks only penetrated slightly into the surface of the flanges. The installed clamping blocks appeared to meet the shape and dimensional requirements of older style clamping blocks issued by the engine manufacturer. The other marks were wider with curved ends that did not match any feature of the older style installed clamping blocks. A small step was apparent at the edge of the larger contact area indicating removal or displacement of material from the surface. The marks did however appear to match the configuration and shape for newer style clamping blocks introduced by the engine manufacturer on engines produced after March 1985. According to the engine manufacturer, the change was instituted as a production product improvement and the use of the newer clamping blocks was not a mandatory requirement on the engine installed in this airplane. According to the magneto manufacturer, the magneto housings are stripped of paint and dipped into a dichromate bath for corrosion prevention during the remanufacturing process. They were subjected to an inspection for cracks, but the inspection was only visual.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: fatigue failure of the dual magneto mounting flanges that resulted from undetected contact damage sustained during a previous installation, which resulted in its separation from the engine during take-off. Full narrative available
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