What happened
On December 13, 2006, a Bell UH-1D helicopter was performing external load operations near the Pitirishca sector in Ecuador. The aircraft was engaged in transporting timber using a long-line sling system. During its thirteenth flight of the day, as the crew approached the designated discharge point, the aircraft experienced a sudden rightward bank. This maneuver caused the external load to become unstable and begin a pendulum motion.
As the load swung, it struck the treetops. Although the onboard mechanic instructed the pilot to reduce speed and maintain altitude, the aircraft entered an uncontrolled descent. The heavy load eventually struck the ground and dragged for approximately 25 meters before becoming anchored in a muddy pit. This sudden anchoring forced the helicopter into a violent impact with the terrain roughly 50 meters ahead of the intended discharge area. The crash resulted in one fatality among the crew and caused severe damage to the aircraft.
The investigation
The investigation focused on the flight dynamics, crew training, and aircraft maintenance records. Investigators examined the sequence of events leading from the initial bank to the final impact. The board analyzed the pilot's experience, noting that while he had significant flight time in Bell 212 helicopters, there was no documented evidence of specific training or recurrent instruction for the Bell UH-1D or for long-line external load operations.
Technical analysis of the engine and components showed no signs of mechanical failure or fuel contamination. The investigation also scrutinized the aircraft's weight and balance, finding that while the aircraft was within structural limits, it was operating with various parts from different Bell models (204, 205, and 212) without clear traceability regarding their remaining service life.
Findings
- The primary cause of the accident was the pilot's failure to release the external load after it made contact with the treetops.
- A sudden reduction in airspeed from 65 knots to 35 knots, occurring in just 2.9 seconds, contributed to the destabilization of the load.
- The pilot failed to utilize the manual emergency release system when the situation escalated.
- The electrical release system was not set to the "on" position during the operation.
- The pilot lacked documented training and experience specifically for long-line external load operations in the Bell UH-1D.
- There were no records of recurrent training for the crew regarding these specific types of heavy-lift maneuvers.
- The aircraft was operating with components from various models without verified service life traceability.