What happened
On June 24, 2018, at approximately 12:30 h, an Elicop amphibious ultralight helicopter, registration I-C435, was performing a takeoff from a parking area near the Baells Reservoir in Cercs, Barcelona. The pilot had previously landed at the site to check the engine after an oil pressure warning light had illuminated during the flight. Upon deciding to continue the flight toward Montmeló, the pilot departed with a tailwind and executed a very sharp right-hand turn to utilize the wind for climbing.
During this maneuver, the main rotor blade struck a medium-voltage electrical line (LMT 25kV OLVAN) near the C-26 highway. While the impact did not sever the cables, the tension caused two parallel cables to detach from their supports. One end of the fallen cables landed in the reservoir, while the other struck a roadside guardrail, causing an electrical arc. The pilot, unaware that a strike had occurred, continued the flight and landed safely at the Montmeló racing circuit helipad without noticing any vibrations.
The investigation
The CIAIAC investigation examined the flight sequence, the mechanical state of the aircraft, and the pilot's operational procedures. Investigators noted that the pilot was experienced with the area and frequently flew similar routes without formal planning. The investigation also clarified the aircraft's status, confirming it was an amateur-built ultralight helicopter rather than a standard Robinson R-22, as suggested by some documentation.
Technical analysis of the electrical lines confirmed that the cables failed due to tension (stretching) rather than an electrical arc at the point of impact. The investigation also reviewed the pilot's engine maintenance, noting that the engine was operating with approximately 4 liters of oil, which was below the required 5.5-liter minimum.
Findings
- The primary cause of the incident was the total absence of flight planning, which led to the execution of an extremely tight turn within a confined area with reduced visibility.
- The pilot performed a high-bank maneuver in a restricted environment, significantly obscuring the view of overhead obstacles.
- The takeoff was performed with a tailwind, which decreased the aircraft's performance capabilities during the critical climb phase.
- The pilot failed to conduct or properly execute a pre-flight inspection, as evidenced by the failure to detect insufficient oil levels prior to departure.
- The presence of medium-voltage lines in the area made the obstacle difficult to identify, especially given the terrain and the pilot's maneuver.