What happened
On August 7, 2019, an AS350 B3 helicopter, registration PR-EAM, operated by the Amazon State Public Security Secretariat, was performing a police mission takeoff from Flores Aerodrome in Manaus, Brazil. Shortly after leaving the ground, the aircraft began an uncontrolled turn to the left. The crew was unable to regain control as the spin accelerated and the aircraft gained altitude. The helicopter subsequently performed a hard landing approximately 10 meters from the takeoff point. While the main and tail rotor blades did not strike the ground, the aircraft sustained substantial damage to the tail cone and horizontal stabilizer, along with light damage to the landing skids and tail rotor. All six occupants—two pilots, two tactical air operators, and two passengers—were unharmed.
The investigation
CENIPA's investigation focused on the flight dynamics and the crew's actions during the critical moments of takeoff. Investigators examined the pilots' flight experience, noting that while both were qualified, they possessed very little experience specifically with the AS350 B3 model. The investigation also reviewed the aircraft's maintenance and weight and balance records, finding that while the aircraft was within weight limits, the weight and balance calculations were being performed using a table belonging to a different aircraft in the operator's fleet. Furthermore, the investigation looked into the organizational culture of the operator, identifying a lack of formal Standard Operating Procedures (S/OP) and a lack of structured training programs.
Findings
- Incorrect pedal application: The pilot flying applied the left pedal to the end of its stroke, which caused the aircraft to complete a 360-degree turn in just 4.5 seconds. This error may have been caused by a mental model mismatch, as the pilot had previous experience in a Schweizer S300, which requires left pedal application to counteract torque in the opposite direction of the AS350 B3.
- Lack of coordination: There was no positive handover of controls between the pilot flying and the pilot in command. The pilot in command attempted to intervene without communicating, leading to uncoordinated and simultaneous inputs on the flight controls.
- Procedural non-compliance: The crew failed to perform the required takeoff and hover check procedures, which could have identified the control issues before the spin intensified.
- Training and oversight deficiencies: The operator lacked a formal training program and adequate management supervision to ensure adherence to flight manuals and safety procedures.