What happened
On June 25, 2020, a Bell 206B helicopter, registration EC-EXE, operated by Bigas Grup Helicopters, was performing an instrumental reconnaissance flight to inspect electrical power lines near Cubillo del César, Burgos. The mission involved visual, photographic, and thermographic inspections to detect defects or vegetation growth affecting the power lines.
After approximately 1 hour and 40 minutes of flight, the crew prepared to land at a site identified by ground support personnel for refueling. The landing area was an unprepared and unassessed terrain. During the final approach, the pilot experienced momentary control issues with the cyclic. The helicopter executed a hard landing, causing the tail rotor and vertical stabilizer to strike the ground. All three crew members on board were uninjured and evacuated the aircraft safely.
The investigation
The CIAIAC investigation examined the flight data, including GPS records, to reconstruct the approach maneuver. The investigation found that the aircraft transitioned directly from the inspection point to the landing site without ascending to the required 500 ft altitude. The approach was completed in only 22 seconds, indicating a lack of adequate preparation.
Investigators noted that the pilot performed the approach turns to the left, which was the least favorable direction for visibility given the pilot's seating position on the right side of the cockpit. Furthermore, the investigation established that the pilot did not perform the five mandatory pre-landing actions required by the operator's manual for unassessed terrain, which include high and low reconnaissance flights and a power check.
Findings
- The primary cause of the accident was the inadequate execution of the approach maneuver due to a failure to adhere to the operator's established procedures.
- The approach was conducted with very low safety margins, characterized by low airspeed, high density altitude, and a high rate of descent.
- The aircraft encountered gusty and likely turbulent tailwind conditions during the turn from base to final.
- The pilot did not perform a power check, which would have revealed the aircraft's performance limitations under the prevailing conditions.
- The landing site was selected by ground personnel who lacked formal training in selecting landing zones.
- The aircraft sustained significant damage to the tail boom, skids, tail cone, vertical stabilizer, and tail rotor.