What happened
N58318, a Hughes 369 helicopter operating under contract for the U.S. Geological Survey, was inbound from the southeast to land at Ketchikan-Temsco Heliport (6Z4). Simultaneously, N73WS, a Cessna 185 amphibian aircraft, was departing from the southeast of Ketchikan International Airport (KTN). The airspace involved, known as the Tongass Narrows, is flanked by mountains to the northeast and southwest. Reported weather conditions included scattered clouds at 500 feet, broken clouds at 1,100 feet, and overcast skies at 2,200 feet, with visibility of five miles in light rain and fog.
To approach 6Z4 via visual flight rules, N58318 had to navigate up the narrows, passing over or near KTN. Although KTN lacked a control tower, regulations required two-way radio communication with the Ketchikan Flight Service Station (FSS) for operations below 3,000 feet and within three miles of the airport. At 13:18:58, N58318 reported its position at Gravina Point, approximately four miles southeast of KTN, and received traffic advisories from the FSS. Shortly after, at 13:19:19, N73WS reported its departure intentions and was provided with traffic information regarding N58318.
N73WS departed KTN using the parallel taxiway adjacent to Runway 11, in accordance with local traffic flow agreements. Nearly one mile southeast of KTN, the two aircraft collided while N58318 was flying near the extended centerline of Runway 11. N58318 crashed into the water, resulting in fatal injuries for those on board. N73WS returned to Ketchikan and crash-landed at the airport. Aviation data indicated heavy traffic volume in the vicinity of KTN during the May to September period.
The investigation
The investigation examined the flight paths and communication logs between the aircraft and the Flight Service Station. Evidence confirmed that both pilots had received traffic advisories regarding each other's positions prior to the collision. The proximity of the two aircraft to the extended centerline of Runway 11 was identified as the critical factor in the incident.
Findings
Contributing factors included the complex terrain of the Tongass Narrows and the high density of air traffic in the area. The lack of a control tower at Ketchikan International Airport placed the responsibility for separation on pilot vigilance and adherence to advisory procedures. The collision occurred despite both parties receiving timely traffic information, highlighting the challenges of visual flight rules operations in confined, mountainous environments with limited visibility.