What happened
On October 2, 2003, an HB-350B helicopter, registration PT-HMS, was conducting an operational maintenance and equipment check flight near Guarulhos, São Paulo. The flight originated from Campo de Marte after a recent electrical system inspection. The pilot, accompanied by two passengers, proceeded to the Parque Ecológico do Tietê to perform a simulated hydraulic failure training maneuver.
During the exercise, the pilot intentionally deactivated the hydraulic system, which significantly increases the physical effort required to manipulate the flight controls. As the aircraft approached the ground, the pilot's seat unexpectedly slid backward along its rail. In an attempt to recover the aircraft, the pilot applied rapid collective pitch to initiate a go-around. This sudden application of power, combined with the increased control resistance from the deactivated hydraulics, caused the helicopter to lose directional control and enter a left-hand yaw.
The aircraft's tail boom struck trees, causing the tail rotor drive shaft to break and triggering a sudden drop in engine NG (gas generator) speed. The helicopter subsequently struck the ground, resulting in severe damage to the aircraft. The pilot and one passenger were uninjured, while the second passenger sustained minor injuries.
The investigation
CENIPA's investigation focused on the sequence of events during the maneuver and the mechanical state of the aircraft. Investigators examined the seat mechanism and found no inherent failure in the locking system, suggesting the movement may have resulted from an inadequate pre-flight inspection. The investigation also analyzed the impact dynamics, noting that the main rotor blades broke near the root, indicating the engine was still producing power at the moment of impact. Furthermore, the investigation evaluated the suitability of the training area, noting the lack of necessary infrastructure for such high-risk maneuvers.