What happened
On December 12, 2015, a Piper PA-36-300, registration HK1892, was conducting aerial spraying operations over banana crops in the municipality of Orihueca, Magdalena. After completing an initial pass, the pilot noticed fluctuations in engine RPM and fuel flow during a right-hand turn.
In an attempt to manage the situation, the pilot decided to cease the low-level flight, discharge the chemical payload, and communicate intentions to find a suitable landing site. However, during this procedure, the engine experienced further RPM oscillations before failing completely. The pilot declared a 'MAYDAY' and executed an emergency landing in an unprepared field at the 'La Francisca' lot. The impact caused substantial structural damage to the aircraft, including broken landing gear, engine mount failure, and damage to the wings and propeller, but the pilot escaped the wreckage uninjured.
The investigation
The GRIAA investigation focused on the mechanical failure of the Lycoming IO-540 engine. Post-accident inspection of the engine revealed several critical failures, including a fractured crankshaft at the number five connecting rod position, a broken camshaft gear, and a fractured oil pump drive shaft. Visual examination of the crankshaft fracture surface showed "beach marks," which are characteristic of metal fatigue.
The investigators also noted that the operator, FUMIGARAY S.A.S., declined to fund the advanced metallographic and root-cause analysis requested by the GRIAA, which would have helped determine the specific origin of the fatigue. This refusal constituted a violation of Colombian aeronautical regulations regarding investigation costs.
Findings
- The primary cause of the engine power loss was the sudden fracture of the crankshaft at the number five connecting rod position, resulting from material fatigue.
- The pilot was properly licensed, medically certified, and the aircraft was in compliance with all maintenance and airworthiness requirements at the time of the incident.
- Meteorological conditions were visual (VMC) and did not contribute to the accident.
- The aircraft's structural damage was a direct result of the impact with the unprepared terrain during the forced landing.