What happened
On the evening of May 23, 2003, a Eurocopter EC-135, registration EC-IKB, was returning to its base in Astorga after completing a medical evacuation flight from Salamanca. The crew included the pilot, a physician, and an air transport technician. During the flight, the physician noticed that a passenger door was not properly secured and advised the pilot to land and rectify the issue.
While descending toward a flat, clear area at approximately 50 feet, the physician spotted medium-voltage power lines directly ahead and alerted the pilot. By the time the pilot identified the cables, they were only about 10 meters in front of the aircraft at eye level. To avoid a sudden, potentially dangerous maneuver, the pilot maintained a level flight path. The cables struck the cockpit windows and slid into the main rotor, where they were severed. The helicopter completed a controlled, smooth landing on the ground.
There were no fatalities or injuries among the three occupants. The aircraft sustained minor damage, including broken cockpit glass, damage to the ELT antenna, and electrical arcing on the main rotor blade pitch links. The impact severed three 15 kV power lines, causing a local power outage.
The investigation
The CIAIAC examined the circumstances surrounding the collision, focusing on visibility, aircraft configuration, and the effectiveness of protective equipment. The investigation noted that the pilot was operating in poor visibility conditions characterized by haze and heavy cloud cover.
Investigators also evaluated the presence of a Wire Strike Protection System (WSPS). The Eurocopter EC-135 involved did not have a cable-cutting kit installed. The investigation analyzed various mitigation strategies, including the use of cable detectors, visual markers (such as orange spheres), and crew training, noting the significant economic and practical challenges associated with implementing these solutions on a wide scale.
Findings
- The primary cause of the incident was the pilot's inability to detect the power lines due to the combination of low-altitude maneuvering and poor visibility.
- The decision to maintain a level flight path rather than performing abrupt maneuvers prevented more severe damage to the aircraft.
- The aircraft lacked a wire strike protection system, which could have potentially mitigated the damage to the rotor components.
Safety action
- REC 16/03: It is recommended that helicopter operators performing frequent low-altitude flights in areas with high or medium-voltage power lines install wire strike protection devices on new aircraft added to their fleets, provided such kits are available for those models.