History of Flight
On November 2, 2013, at approximately 1141 mountain standard time, an experimental Rovey Vans RV-8 airplane, registration N391V, made a forced landing following an engine vibration and partial loss of engine power near Wickenburg, Arizona. The owner/builder/pilot operated the airplane under 14 Code of Federal Regulations Part 91 as a personal flight. The pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from Wickenburg Municipal Airport (E25) around 1100.
The pilot was participating in a Sport Air Race League cross-country event, a 130-mile course departing from and concluding at Wickenburg Municipal Airport. About 13 miles west of E25 at 1,200 feet agl, at maximum power and rpm, he felt an immediate and sustained vibration, which he attributed to the engine or propeller. He radioed a mayday and noted the airplane began to slow. Unable to land on US Highway 60 due to traffic, he turned toward Forepaugh Peak Road. At approximately 150 feet agl, he realized the airplane would not glide far enough and landed on the desert floor. After traveling through vegetation and brush, the airplane came to rest in a nose-down attitude.
Post-Accident Examination
Following the forced landing, the pilot borrowed a club propeller, bolted it to the engine, and performed a ground run with no mechanical problems. The engine was later disassembled at a repair station for a propeller strike inspection and rebuild; no mechanical anomalies were found. The propeller hub was removed and examined at Ottoeson, Phoenix, Arizona, under an FAA inspector's supervision. The inspector noted evidence of loading on the propeller hub at impact and reported that the accident propeller pin had broken, which is unusual in typical propeller strike accidents. Engine performance downloads indicated the propeller pin likely broke during flight.
Metallurgical Findings
The propeller blades, hub case, and hub bearings were sent to the NTSB metallurgical laboratory. The hub had been disassembled prior to arrival. Bearing and hub surfaces were in good condition with no abnormal wear or pre-impact damage. Propeller blades showed gouging and scratches along their longitudinal axes, with tip damage primarily on leading edges, consistent with ground impact. One pitch change pin had fractured from the hub face along the bend radius. The pin fracture surface was smeared, but the mating side on the hub face was undamaged. Crack arrest and ratchet marks indicated progressive cracking covering about 70 percent of the fracture surface. The fatigue crack initiation site had multiple surface cracks, with the primary site corresponding to a surface depression. The pin and hub surfaces had a dimpled, pockmarked texture consistent with shot peening. Chemical composition analysis using EDS and XRF, along with hardness testing, revealed discrepancies in the material composition. A detailed report is in the accident docket.