What happened
On March 9, 2021, at approximately 11:30 UTC, a Cessna A188B agricultural aircraft, registration PR-THT, was performing a pesticide application flight over a plantation at Fazenda Sanitá, located in Quirinópolis, Goiás. During one of the flight passes, a propeller blade fractured, forcing the pilot to perform an emergency landing in the plantation.
The aircraft sustained substantial damage during the impact, but the pilot emerged from the occurrence uninjured.
The investigation
CENIPA investigators examined the McCauley propeller (model D2A34C98-0) to determine the cause of the structural failure. The investigation found that the propeller had undergone a 50-hour inspection only 31 days prior to the accident and had been certified as airworthy at that time.
Technical analysis of the fracture surface revealed that the blade failure was caused by material fatigue. The investigation established that this fatigue was initiated by an impact from foreign object debris (FOD), which created a nick on the leading edge and intrados of the blade. This nick acted as a stress concentrator, leading to the subsequent propagation of a fatigue crack.
According to the manufacturer's manual, the damage caused by such objects is classified as "acute damage," which requires immediate repair to prevent structural failure. The investigation noted that while the aircraft's maintenance records were up to date, there may have been a failure to identify this specific discrepancy during the pre-flight inspection.
Findings
- The propeller blade failure was caused by material fatigue induced by foreign object debris (FOD) impact.
- The impact created a stress concentrator on the blade's leading edge.
- The pilot was fully qualified with a valid medical certificate and sufficient flight experience.
- The aircraft was in an airworthy condition with valid documentation and within weight and balance limits.
- Meteorological conditions were favorable for visual flight operations.
Safety action
- It is recommended that the National Civil Aviation Agency (ANAC) share the lessons learned from this investigation with the operator, Textor Aviação Agrícola Ltda., to emphasize the critical importance of thorough pre-flight inspection procedures.