NTSB Identification: CEN11LA555
14 CFR Part 91: General Aviation
Accident occurred Sunday, August 07, 2011 in Millsap, TX
Probable Cause Approval Date: 12/11/2012
Aircraft: PIPER PA-28-180, registration: N7698W
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot had just leveled off to cruise flight when the airplane jerked and began to vibrate violently. The pilot secured the engine and made a forced landing on a road. A postaccident examination revealed that an 18-inch section of one of the propeller blades had separated. Metallurgical examination of the remaining blade section revealed striations on the fracture surface consistent with high-cycle fatigue. At least three crack arrest marks were observed, which was consistent with the stopping and starting of the cyclic stresses. The propeller had accumulated 165.73 hours since being overhauled in 2004. The most recent 100-hour inspection was completed about 10 months before the accident. The Federal Aviation Administration issued Airworthiness Directive (AD) 69-09-03 R3 in 1996 to prevent propeller blade tip fatigue failure. The directive required that pilots avoid continuous operation between 2150 and 2350 rpm. The failure mode of the blade was consistent with it operating in the restricted rpm range. Due to the multiple arrest marks found in the examination, the fatigue crack had propagated over multiple flight cycles. It could not be determined when the fatigue crack was initiated.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A sudden loss of engine thrust due to the separation of a propeller blade in cruise flight due to high cycle fatigue.

Full narrative available

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