What happened
On November 10, 2013, an AS-355N helicopter, registration PR-HBE, operated by Helibarra Táxi-Aéreo Ltda, was performing an external load transport operation in Acarapi, Almeirim, Pará. While the pilot was performing a low-altitude hover to attach a load to the aircraft's hook, the tail rotor collided with another cargo item positioned within the approach sector.
The impact severed the tail rotor and tore away the rear transmission. This loss of anti-torque control caused the aircraft to yaw sharply to the left. The pilot responded by applying right pedal and reducing torque, successfully executing an emergency landing in a nearby soccer field. The pilot was uninjured, though the aircraft sustained substantial damage to the tail rotor, rear transmission, and the front of the right skid.
The investigation
CENIPA's investigation focused on the operational procedures and the physical arrangement of the cargo at the site. The investigation established that the pilot was monitoring the load master through a rearview mirror rather than using a dedicated signal person (signaler) to guide the aircraft's position.
Investigators also reviewed the operator's external load manual. While the manual required a 3-meter lateral separation between loads, it lacked any requirement for a minimum longitudinal distance between rows of cargo. Furthermore, the manual's emergency procedure for a sudden landing required the pilot to maneuver the aircraft to the left, which was the same direction the aircraft naturally yawed following the tail rotor failure.
Findings
- Inadequate spatial assessment: The pilot judged that the arrangement of the cargo would not pose an obstacle, but the proximity of the loads reduced the safety margins required to maintain a stable hover.
- Lack of visual guidance: The operation was likely being conducted without a signaler, forcing the pilot to rely on a rearview mirror, which limited the ability to detect aircraft drift.
- Incomplete operational procedures: The company's external load manual did not establish a minimum longitudinal distance between cargo rows, which could have prevented the tail rotor from striking an obstacle.
- Inaccurate flight control: The pilot's control inputs during the hover were not precise enough to maintain the aircraft within the safe operational margins.