Accident Overview
On August 2, 2021, at approximately 0930 mountain standard time, a Piper PA-28-140 airplane, registration N44245, was substantially damaged during a forced landing near Amado, Arizona. The pilot and pilot-rated passenger were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Flight and Forced Landing
The pilot reported that while in level cruise flight at about 6,000 feet mean sea level, the airplane suddenly began to vibrate. He checked the magneto switch and scanned the instruments for cylinder anomalies but found none. Deciding to shut down the engine to stop the vibrations, he soon realized he was committed to a forced landing in a nearby field. The pilot stated that during the approach, he was traveling too fast and attempted to reach an adjacent field beyond a tree line and fence. During the landing, the right wing struck a tree, and the airplane subsequently landed hard in a muddy field. The nose landing gear collapsed upon touchdown. Both the pilot and passenger exited the aircraft without injury.
Aircraft Damage
Examination of accident site photos revealed the right wing remained attached to the rear spar but had separated at the main spar near the wing root and was bent upward. The outboard section of the right wing was buckled, and the leading edge showed circular impact damage. The fuselage was buckled near the firewall and near the empennage. One propeller blade had separated about 5 inches outboard of the blade root; the separated portion was not found. The remaining blade section was retained for further examination.
Propeller Examination
Review of propeller logbooks indicated the propeller was installed on the accident airplane on March 17, 2020, with 116.1 hours of operation since overhaul. The last annual inspection was completed on April 10, 2021. At the time of the accident, the propeller had accumulated about 245 hours since overhaul. Examination of the retained propeller blade section by the National Transportation Safety Board Materials Laboratory revealed a fatigue crack that had initiated near the trailing edge of the blade. Red transfer marks were found near the trailing edge. The fatigue crack initiated at multiple sites along the blade face surface adjacent to the trailing edge. The edge area exhibited indications of copper, iron, and manganese, indicating material transfer from an alloy dissimilar to that of the blade material.