NTSB Identification: SEA99LA174.
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Accident occurred Sunday, September 26, 1999 in VAUGHN, WA
Probable Cause Approval Date: 11/02/2000
Aircraft: Piper PA-28-180, registration: N9395J
Injuries: 4 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.

While in cruise at 2,000 feet altitude and 2,000 RPM there was a sudden loud noise and vibration. The pilot reduced power and executed an emergency landing. Post-landing examination of the aircraft revealed that approximately six inches of one propeller blade had separated from the propeller. The Sensenich Corporation, fixed pitch, aluminum propeller, model 76EM8S5-0-60, was submitted to the Safety Board's Materials Laboratory, Washington, DC, for further metallurgical examination. The examination revealed a flat, chordwise fracture area that contained crack arrest positions and radial marks typical of fatigue cracking. Microscopy revealed that the origin area was located within a notch at the leading edge at the flat side of the blade. The depth of the notch was about 0.008 inch. The leading edge of the blade contained sanding marks, typical of a blend repair, in the vicinity of the notch. The sanding marks did not extend into the deepest part of the notch, directly adjacent to the fracture surface at the origin area. FAA Advisory Circular 43.13-1A, Section 3 'Repair of Metal propellers,' paragraph 585(a) discusses procedures applied to the repair of aluminum propellers. Specifically, this reference addresses rounding out of nicks, scars, cuts, etc. by advising '...exercise care to remove the deepest point of the injury.' The total time on the propeller was unavailable and the party who executed the propeller dressing procedure was not known.

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

The separation of a propeller blade tip due to fatigue, and the improper maintenance procedure.

Full narrative available

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