What happened
On July 9, 2003, an H-3/50 helicopter, registration PT-HLO, was conducting a forest patrol mission near Boca do Acre, Amazonas, to monitor controlled deforestation. After approximately three hours of flight, the crew was requested to land in a restricted area—a clearing surrounded by trees roughly 30 meters in height—to allow IBAMA technicians to inspect timber extraction activities.
During the approach, the pilot placed the front of the skids on the ground, but the aircraft's tail began to sink due to the steep upward slope of the terrain. In an attempt to stabilize the helicopter, the pilot applied excessive collective and cyclic inputs. This maneuver caused the aircraft to surge forward by approximately three meters, leading the main rotor to strike nearby trees. The impact caused the main rotor to detach, and the helicopter overturned on its left side.
The investigation
CENIPA's investigation focused on the crew's decision-making and the technical limits of the aircraft during the landing. The investigation established that the terrain's incline exceeded the H-350's manual limits for landing (which specifies a maximum of 10 degrees nose-up).
Investigators examined the crew's coordination and training, noting that while the pilot was properly licensed and the aircraft's maintenance was up to date, there was no documented evidence of specific training for landing in restricted jungle environments. Furthermore, the investigation looked into the communication between the pilot and the aerial observer, noting that while the observer alerted the pilot to the slope, the information did not prompt an abort of the landing.
Findings
- The pilot applied excessive control inputs in an attempt to stabilize the aircraft, which directly caused the forward movement into the trees.
- The crew's judgment was flawed, as they proceeded with the landing despite being informed of the terrain's incline.
- Mission planning was inadequate, as potential landing sites and associated risks had not been identified prior to the flight.
- There was a lack of specific training for the crew regarding approach and landing procedures in restricted jungle environments.
- The aerial observer failed to be assertive enough in communicating the risks of the slope to the pilot.
- The aircraft's tail sank excessively because the terrain slope exceeded the manufacturer's operational limits.