What happened
On November 29, 2001, an AS-350 B2 helicopter, registration PT-YAM, was conducting a low-altitude observation flight over the Rio das Antas Valley in Pinto Bandeira, Rio Grande do Sul. The mission, operated by Aeromed Serviço e Táxi Aéreo Ltda., was intended to survey the area for the State Secretariat of the Environment regarding the construction of hydroelectric reservoirs.
While flying at an altitude of approximately 700 meters, the aircraft struck a single-phase 13.8 KV electrical distribution wire. The impact caused the wire to wrap around the main rotor mast, forcing the helicopter into a vertical descent. The aircraft crashed in a wooded area, and the subsequent impact with the ground triggered a fire. There were five fatalities among the occupants, consisting of the pilot and four passengers.
The investigation
CENIPA investigators examined the wreckage and the surrounding infrastructure. The investigation established that the electrical line, operated by RGE, lacked the mandatory warning markers (such as orange or red spheres) required by Brazilian technical standards (NBR 7/276 and Portaria 1141/GM5) for lines crossing rivers.
Technical analysis revealed that the wire was a galvanized steel cable with a diameter of only 3.09 mm. Due to its small size and the lack of visibility aids, investigators concluded that detecting the cable under the flight conditions was practically impossible for the crew. The investigation also noted that while the pilot was highly experienced, his IFR certification had expired.
Findings
- The lack of warning signage on the electrical transmission lines significantly hindered the crew's ability to identify the obstacle.
- The pilot demonstrated inadequate judgment regarding flight altitude, failing to maintain sufficient vertical separation from the power lines.
- Inadequate flight planning for low-altitude operations may have contributed to a lack of situational awareness.
- Potential overconfidence in the pilot's familiarity with the region may have led to a failure to properly assess the risks associated with the terrain and obstacles.