Cessna 172S N427CP incident near Jackson, Mississippi

Probable cause

The separation of the propeller blade tip due to fatigue cracking that initiated at the blade’s leading edge.

NTSB analysis

According to the pilot, he conducted a thorough preflight inspection of the airplane with no anomalies noted. Then, when the airplane was at an altitude of 7,000 feet mean sea level, an extreme vibration began. The pilot reduced engine power, verified the airplane’s flight controls were still operational, and declared an emergency with the air traffic controller that he was in contact with. As the vibration continued, the pilot elected to shut down the engine and, as the propeller was windmilling, the vibration continued. The pilot reduced the airspeed in order to stop the propeller rotation, then immediately obtained best glide airspeed once the propeller stopped. As soon as the propeller stopped windmilling, the vibration ceased. The pilot landed the airplane without incident and it was towed to the fixed base operator. A postincident engine teardown revealed that there were no anomalies that would have precluded normal operation. Examination of a fracture surface on one of the propeller blades revealed that the blade tip failed as a result of fatigue cracking that initiated at the leading edge of the blade. The propeller blade was inspected about 72 operating hours before the incident, as part of the airplane’s 100-hour annual inspection, and no discrepancies were noted at that time.

Text from the NTSB. Open the NTSB docket for ERA12IA169 for the full record.