What happened
On December 11, 2008, an AS 350 B2 helicopter, registration PR-YSJ, was performing a flight over the Tocantins River in Itupiraxia, Pará, with two pilots and three passengers on board. While the flight initially maintained an altitude of approximately 200 feet, the aircraft began flying at extremely low altitudes, ranging between 10 and 50 feet, following a maneuver to clear a sandbar.
During this low-level transit, the passengers noticed a continuous loss of altitude. Although the left skid made contact with the water, the aircraft struck the river surface with a low angle of approach. The impact caused the tail rotor to strike the water, leading to the breakage of the tail rotor blade and the drive shaft. This resulted in a total loss of control, and the aircraft submerged in the river. All five occupants managed to egress the aircraft and sustained minor injuries.
The investigation
CENIPA's investigation focused on the flight profile and the decision-making process of the crew. Investigators examined the aircraft's maintenance logs, which revealed that the operator was not adhering to the manufacturer's established maintenance program, with several inspections being performed cumulatively rather than at the prescribed intervals.
The investigation also analyzed the crew's performance, noting that the commander reported experiencing "mental fatigue" on the day of the accident. Furthermore, the investigation looked into the organizational culture of the GRAER-PA unit, which lacked sufficient oversight to ensure compliance with operational limits and air traffic regulations.
Findings
- The pilot's excessive cyclic input following the initial water contact caused the tail rotor to strike the river, leading to the loss of control.
- The commander failed to follow Crew Resource Management (CRM) principles by ignoring the co-pilot's advice to climb and failing to communicate the reasons for maintaining such a low altitude.
- The flight violated established air traffic regulations (ICA 100-4), which required a minimum altitude of 200 feet, making vertical separation from the river impossible to maintain.
- The commander's flight planning lacked proper operational risk management, as the low-altitude flight profile was not coordinated with the co-pilot.
- An organizational culture existed within the unit that allowed the commander to make operational decisions that bypassed established safety limits and regulations.
- The pilot's use of tree canopies as a visual reference contributed to visual illusions regarding the aircraft's actual altitude above the water.