Accident Details
The airplane sustained minor damage when it nosed over during an emergency landing. The emergency landing followed an in-flight loss of a propeller blade tip. The pilot was uninjured.
According to the pilot, while conducting an actual spray run, the aircraft began to shake and vibrate violently. The pilot shut down the power and climbed about 100 feet to look for a suitable landing area. The terrain consisted of rolling pasture land and a cornfield, with no roads available for landing. After rolling out for a short while in the corn, the landing gear became stuck in corn and soft sandy soil.
Propeller Examination
A portion of the remaining blade, including the separation point, was sent to the NTSB's Materials Laboratory Division for examination. The laboratory report stated that a large portion of the fracture surface was on a 90-degree flat plane with multiple ratchet marks and crack arrest marks, features typical of a fatigue crack. The fatigue crack originated from multiple origins at the bottom of a gouge on the flat face of the blade, approximately 2.25 inches from the blade's leading edge. The fatigue crack extended through about two-thirds of the blade's cross-section. The remaining one-third of the fracture surface was on a 45-degree slanted plane, typical of an overstress region stemming from the fatigue crack.
A section containing the fatigue origin was saw cut from the fracture. The paint was removed from the areas near the crack origin, and the surface was re-examined with a scanning electron microscope (SEM). The gouge measured 0.6 inch (1.5 millimeters) in length and 0.0055 inch (0.14 millimeters) in depth. Optical examination of the flat face of the blade near the gouge showed no evidence of blending or rework in that area.
Maintenance History
The propeller's last overhaul was completed on January 13, 1998. The propeller had accumulated 240 hours of flight time since that overhaul.