Socata TB10 N189TB incident near Pawtucket, Rhode Island

Probable cause

The in-flight separation of the propeller blade tip due to a fatigue fracture.

NTSB analysis

During departure, as the airplane reached an altitude of about 800 feet above ground level, the tip of one propeller blade separated. The flight instructor returned the airplane to the runway and landed without incident. The separated blade tip was not located; however, the remaining section of propeller blade was examined, and a fracture analysis was performed. The results of the analysis revealed fatigue crack propagation, followed by a final overstress fracture. The fatigue crack origin could not be accurately determined because the pertinent portion of blade’s leading edge suffered from postfracture damage, which likely occurred during removal or shipment. This postfracture damage also precluded determination of fatigue crack growthe timing or propagation. However, the fatigue and overstress fractures were consistent with other blade tip fractures that have occurred as a result of excessive vibrations within the propeller blade, typically as a result of a propeller ground strike.

The incident airplane’s propeller blades were manufactured 32 years before the incident, and the manufacturer imposed no life limits on the blades as long as they passed the required overhaul inspections. The incident propeller blades were overhauled twice in the 3 years before the incident. The first overhaul was performed as a result of a propeller strike, and the reason for the second overhaul was not documented. At the time of the incident, the blades had accumulated 852 hours since the most recent overhaul, which occurred 18 months before the incident.

Text from the NTSB. Open the NTSB docket for ERA12IA459 for the full record.