Accident Overview
On 7 April 2010 at 13:30 local time, a Piper PA-28-161 registered LN-TOS operated by Tromsø Flyklubb collided with a cable car wire in Kåfjorddalen, Troms, Norway. The aircraft was being flown by a pilot with one passenger. During a climb-out after the second pass over the passenger's childhood home, the aircraft hit the wire approximately 416 ft above the ground. The impact tore off parts of the tail and right wing. The pilot regained control and subsequently landed at Tromsø Airport Langnes without further damage. Both occupants were uninjured.
Flight Details
The flight originated from Tromsø Airport Langnes. The planned route was based on visual flight rules and included a passage over Kåfjorddalen. The pilot had marked a power line crossing at Løkvollen with a red circle on his map, but the cable car wire was not identified on the map and therefore not marked. The aircraft departed at 12:15 after a 45-minute delay due to fuel system issues. Weather was fine with calm winds.
Obstacle Warning System
The cable car wire was equipped with an Obstacle Collision Avoidance System (OCAS) designed to provide visual and aural warnings. However, neither the warning lights nor the aural warning transmitted via the VHF radio were detected by the pilot. The investigation revealed that the warning lights were ineffective. Additionally, the OCAS aural warning was only permitted on six specific frequencies, which did not necessarily correspond to the radio frequencies in use in the area. Manual selection was required for the warning to be received.
Investigation Findings
The investigation by the Accident Investigation Board Norway (AIBN) noted that the pilot exposed himself to significant risk by flying low in a narrow valley. The cable car was difficult to detect on the map used and hard to spot from the air. The AIBN also identified that the Norwegian Civil Aviation Authority had not given sufficient focus to issues regarding the OCAS system's operational approval, and that there were weaknesses in how information about OCAS was communicated to key user groups. Three safety recommendations were issued. No probable cause was explicitly stated in the available report summary.