On December 27, 1984, a Piper PA-23-250 (registration N6505Y) operated by Appalachian Aviation was involved in an aviation accident near New Philadelphi, OH. Investigators recorded the probable cause as: Fatigue failure of the left propeller bolts due to multiple initiation sites, resulting in propeller separation and subsequent damage to the nose structure. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot experienced vibration and power loss before hearing a thud. The left propeller had separated, damaging the nose. Metallurgical analysis revealed bolt fatigue.
What happened
The pilot reported feeling significant vibration accompanied by a reduction in power output on both engines, prompting an immediate move to idle thrust. Shortly thereafter, a distinct thud was heard inside the cockpit. Upon inspection after the event, it was discovered that the left propeller had completely separated from the aircraft. The detached component cut through the nose section as the plane departed the area. Recovery of the propeller was unsuccessful, and it was not located. Two of the six propeller bolts remained attached to the airframe.
The investigation
A detailed metallurgical examination was conducted on the two bolts that remained with the aircraft. The analysis revealed signs of fatigue progression stemming from numerous origins within the bolt material.
Probable cause
Fatigue failure of the left propeller bolts due to multiple initiation sites, resulting in propeller separation and subsequent damage to the nose structure.