What happened
On August 5, 2017, a Piper PA25-260, registration HK1784, was performing agricultural spraying operations in the department of Casanare, Colombia. After completing several spraying missions near the Renso airfield, the pilot departed for a return flight to the Villa Verónica base.
Approximately seven minutes into the flight, while at an altitude of 500 feet AGL, the pilot detected a burning rubber odor in the cockpit. Although the alternator appeared to be operating normally, a slight vibration soon developed. This was followed by a loud explosion in the engine, accompanied by smoke and fire entering the cabin, which resulted in a total loss of engine power.
Unable to reach the intended airfield, the pilot performed a forced landing in an unprepared rice field adjacent to the Villa Isabella airfield. During the landing roll, the aircraft struck uneven terrain, causing the plane to flip onto its back. The impact caused substantial structural damage to the airframe, including the wings, horizontal stabilizers, and empennage. An in-flight fire, caused by hot engine components interacting with leaking oil, was extinguished by standing water in the field after the aircraft came to rest. The pilot evacuated the aircraft through the left window and was uninjured.
The investigation
The GRIAA investigation focused on the mechanical failure of the Lycoming O-540-G1A5 engine. Investigators examined the engine components and found that the number 4 cylinder had detached from the crankcase. The inspection revealed that the internal components of the engine had suffered a sudden stoppage due to the failure of the connecting rod and cap assembly.
Technical analysis of the engine parts showed evidence of excessive friction and wear within the number 4 cylinder assembly. The investigation also reviewed the maintenance history, noting that the engine had undergone a major overhaul in late 2016 and had completed 263 flight hours since that service. The aircraft's maintenance records were found to be in compliance with all required Airworthiness Directives (ADs) and service bulletins.