Accident Smyth Sidewinder N492AC, Saturday 14 September 2019

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Date:	Saturday 14 September 2019
Time:	11:25 LT
Type:	Smyth Sidewinder
Owner/operator:	private
Registration:	N492AC
MSN:	002
Year of manufacture:	2003
Total airframe hrs:	60 hours
Engine model:	Lycoming O-320-E2A
Fatalities:	Fatalities: 0 / Occupants: 1
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Tucumcari, New Mexico - United States of America
Phase:	En route
Nature:	Private
Departure airport:	Gallup, NM
Destination airport:	Tucson International Airport, AZ (TUS/KTUS)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
The pilot reported that during cruise flight, the engine momentarily started to run rough before he heard a loud bang followed by a separation of a portion of the propeller blade. The pilot shut the engine down and performed a forced landing to open desert terrain, during which the airplane impacted vegetation, resulting in substantial damage to the left wing.

Postaccident examination of the propeller blade revealed a chordwise fracture across the propeller about 12 inches from the hub. The fracture origin area exhibited a small pit, consistent with progressive crack growth from a flat fracture surface in the area identified as the origin. The pit was likely initiated by corrosion, as it exhibited evidence of chlorine-containing salts. No maintenance logbooks were located for the propeller, and its total time in service and most recent inspection were not determined.

Probable Cause: The in-flight separation of a section of a propeller blade due to a fatigue crack, which resulted in a forced landing.

Accident investigation: