NTSB Identification: MIA04IA088.
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Incident occurred Monday, May 10, 2004 in Daytona Beach, FL
Probable Cause Approval Date: 06/08/2005
Aircraft: Beech A36, registration: N3670S
Injuries: 2 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.
The mechanic stated that he and the pilot were conducting a maintenance test flight, when the incident occurred. He further stated that after takeoff, and during climb to cruise, at an altitude of 1,000 feet AGL, as the pilot reduced power from 2,700 rpm to 2,500 rpm, all of a sudden there was a loud bang, and the airplane started to shudder and shake violently. He stated that the pilot reduced power, and returned for an otherwise uneventful landing. Examination of the airplane revealed that one blade of the three-bladed McCauley propeller appeared to be in negative pitch, and when moved, it revolved freely in the hub. Further examination revealed that the pitch change actuating pin for the No. 3 propeller blade had separated, with a threaded portion of the pin still remaining in the hub. On May 10, 2004, the incident McCauley propeller blade, and associated propeller parts, were examined at the NTSB Metallurgical Laboratory, Washington DC. The examination revealed that for the affected blade, the ferrule hole into which the fractured pitch change actuator pin had been inserted, had threads that did not extend into the hole as specified by the propeller manufacturer. The threads extended about one half the distance from the bottom of the hole, and fatigue cracking was found to be in the threads of the pin, and the fatigue crack had progressed about 95 percent of the way through the pin before it separated due to overstress. Records indicated that the propeller had last been overhauled on January 30, 1997,by a maintenance facility in Johnson City, New York, about 678 flight hours prior to the incident..
The National Transportation Safety Board determines the probable cause(s) of this incident to be: Improper maintenance/installation by the propeller overhaul/repair facility, which resulted in stress related fatigue and the eventual separation of the propeller pitch change pin. Full narrative available
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