Piper PA-28R-200 N4350T incident near Lacon, Illinois

Probable cause

The propeller blade’s failure due to a fatigue crack that originated from a surface gouge that resulted from foreign object damage to the propeller blade that occurred at an unknown time.

NTSB analysis

The pilot reported that he was flying the airplane at 4,500 feet mean sea level with 23 inches of manifold pressure and with the engine at 2,350 to 2,400 rpm when the airplane began to abnormally vibrate. He scanned the instruments and observed no other abnormal indications. He executed an emergency landing to an airport without incident. The examination of the airplane revealed that about 6 inches of a propeller blade tip had separated from the propeller. The metallurgical examination of the fracture surface revealed that a fatigue crack had originated about 0.06 inch from the blade's leading edge. A surface gouge was found at the origin of the fatigue crack, which indicated that the direction of the damage was from the leading to trailing edge consistent with foreign object impact to a rotating propeller. A test of the airplane's tachometer revealed that it was indicating 50 rpm higher than the actual propeller rpm and that it had a restricted propeller operating range from 2,100 to 2,350 rpm. When the pilot set the propeller to 2,350 or 2,400 rpm using the airplane's tachometer, the actual rpm would have been operating within the restricted rpm range.

Text from the NTSB. Open the NTSB docket for CEN12IA377 for the full record.