What happened
On January 13, 2017, a PZL-MIELEC M-18A, registration HK5103, was performing scheduled agricultural spraying operations near the Antonio Roldán Betancourt Airport in Apartadó, Colombia. After completing its second flight of the day, the aircraft was on final approach to runway 15 when the pilot experienced a sudden loss of engine power control.
As the pilot attempted to adjust the throttle, the engine failed to respond to acceleration, preventing the aircraft from maintaining the necessary airspeed. Realizing the aircraft could not reach the runway, the pilot declared an emergency and executed a controlled emergency landing in an unprepared banana plantation approximately 5 nm from the runway threshold. The impact with the vegetation caused the aircraft to stop abruptly, resulting in substantial structural damage to the engine, propeller, wings, and airframe. The pilot evacuated the aircraft without injuries.
The investigation
The GRIAA investigation focused on the mechanical failure of the engine's power control system. Investigators examined maintenance records, which showed that while the aircraft had been undergoing regular inspections, a recent 50-hour service had not adequately inspected the engine control cable's securing mechanism.
Technical analysis revealed that the safety wire (lockwire) securing the throttle cable's locknut had broken. This failure allowed the cable to move beyond its designed range of travel, severing the mechanical connection between the cockpit throttle lever and the carburetor. This disconnection prevented the pilot from increasing fuel flow to the engine, leading to the loss of power during the approach.
Findings
- The primary cause was the breakage of the safety wire in the engine throttle control mechanism, which resulted in a loss of connection between the cockpit controls and the carburetor.
- Inadequate maintenance inspection processes failed to identify the deteriorating condition of the throttle cable's securing hardware during routine services.
- Contributing factors included a lack of adequate quality control supervision by the operator and a lack of clear, specific inspection procedures within the company's Maintenance Manual regarding critical engine control components.
- The pilot's skill in maintaining aircraft control during the low-altitude, low-speed emergency was a significant factor in the survival of the crew and the controlled nature of the impact.