ANC10FA100

Undetermined.

The commercial pilot departed a remote, oceanside lagoon in a float-equipped airplane with three passengers on an on-demand air taxi flight in reduced visibility and heavy rain. When the airplane did not reach its destination, the operator reported the airplane overdue. Extensive search-and-rescue efforts along the coast and inland failed to find the wreckage. After the search ended, small portions of the fragmented airplane washed ashore about 28 miles northeast of the departure lagoon. The remainder of wreckage has not been located despite sonar searches of the ocean near where the wreckage was found. A stowed tent and duffle bag, which were reported to be aboard the airplane, were also found ashore near the wreckage location. The tent and duffel bag exhibited evidence of exposure to a high temperature environment, such as a fire. However, there was no evidence indicating that the fire occurred in flight. The lack of soot on the undamaged areas of the items, as well as the very abrupt demarcation line between the damaged portion and the undamaged material, is consistent with these items floating in the water and being exposed to a fuel fire on the surface of the water, rather than having been exposed to a fire in the airplane’s cargo compartment. Due to the fragmentation of the recovered wreckage, it is likely that the airplane collided with ocean’s surface while in flight; however, because the engine and a majority of the wreckage have not been found, the sequence of events leading to the accident could not be determined.

HISTORY OF FLIGHT On August 21, 2010, about 1412 Alaska daylight time, a de Havilland DHC-2 airplane, N9313Z, sustained substantial damage when it impacted ocean water near Katmai National Park, Alaska. The airplane was registered to and operated by Branch River Air Service, Anchorage, Alaska, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 135 as on-demand air taxi flight. Instrument and visual meteorological conditions prevailed throughout the general area between the point of departure and the intended destination. A company visual flight rules flight plan was active for the flight. Only fragmented portions of the airplane have been found washed up on the ocean shoreline near the presumed crash site. The commercial pilot and three passengers remain missing, and are presumed to have sustained fatal injuries. The flight originated from the Swikshak River Lagoon, Katmai National Park, Alaska, about 1352. The intended destination was King Salmon, Alaska, with an intermediate stop at Lake Brooks, Katmai National Park. Information provided by the National Park Service (NPS) revealed that the DHC-2 was part of a flight of two airplanes that were transporting NPS employees from the Swikshak River Lagoon area back to their assigned posts. When the DHC-2 did not arrive at the Lake Brooks Camp or King Salmon, the flight was reported overdue by the operator to the Federal Aviation Administration (FAA). An Alert Notice (ALNOT) was issued by the FAA on August 21, 2010, at 1750. The United States Air Force Rescue Coordination Center (RCC), United States Coast Guard, and NPS initiated search and rescue operations on August 22, and continued through September 5, 2010. The NPS reported that over 60,000 air miles were flown by various helicopters and airplanes with no evidence of the location of N9313Z. The ALNOT was canceled by the FAA on September 13, 2010. On September 27, 2010, debris from the airplane was found about 28 miles northeast of the departure point by an airplane flying through the local area. On September 28, 2010, the pilot of a helicopter landed in the vicinity of the debris, and verified it was that of the missing DHC-2. During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot of the second company airplane, a Cessna 206, reported that on the day of the accident, he departed with the DHC-2 on the first leg of the accident flight and remained about one mile in trail throughout the flight. The pilot said that the flight proceeded direct to Kulik Lake, Kamishak River, and towards Big River. Upon nearing the passage towards Big River, the pilot of the DHC-2 radioed the pilot of the Cessna, stating that he was turning around. The pilot of the Cessna said that he initiated a 180-degree turn and then heard the pilot of DHC-2 report that he "found a hole" and descended through it overhead of Big River. The pilot of the Cessna then continued flying along the Kamishak River to the north, and followed the coastline to the south and southeast toward the Swikshak Lagoon. About 35 minutes later, the pilot of the Cessna arrived at the Swikshak Lagoon and saw the DHC-2 departing the area to the northeast. He recalled that the pilot of the DHC-2 asked him about the weather along the coast. The Cessna pilot responded and said that the weather was "good" to the north, with a broken cloud layer about 500 feet above ground level (agl) with a southeasterly wind flow of about 40 knots between Cape Douglas and Kamishak Bay, with good visibility. About 20 minutes later, the Cessna pilot departed Swikshak Lagoon and flew along the coastline to the north to McNeil Cove before following the Little Kamishak River. The flight then went along the Kulik River, across Nonvianuk Lake towards the Lagnak drainage before turning south toward King Salmon. The pilot of the Cessna said that during the flight, visibility was at or slightly greater than about 5 miles, cloud ceilings mostly broken around 700 to 1,000 feet mean sea level (msl) with some areas of an overcast layer. He stated throughout the return flight to King Salmon, he remained at a cruise altitude of about 500 feet agl. He added that he was new to the area, and it was his first trip to the coastal area from King Salmon. Information obtained through interviews conducted by the NTSB IIC and written statements from two passengers, who were on the Cessna 206's return flight from the Swikshak river camp to King Salmon, revealed that while on the ground at the Swikshak river camp, about an hour and a half prior to the arrival of the DHC-2, weather conditions around the camp declined, with "low fog clouds creeping in" and that a downpour of rain ensued. One passenger reported that during discussions about what to do if the airplanes could not reach the camp due to the weather, they saw an airplane approaching from the Kaguyak/Big River drainage, and that visibility had increased and the rain diminished. A passenger stated that she assisted docking the DHC-2, and during discussions with the pilot while loading the airplane, he mentioned that he "found a sucker hole that he could get through" in order to find the camp, and would not be returning to the south, as the weather did not look good. The passenger informed the pilot that she was concerned about the weather, and told him that he could stay in camp with them and wait out the weather. However, the pilot responded that he wasn't comfortable doing so, and had to return to King Salmon to fly another trip later in the day. The passenger said that when the DHC-2 departed, she estimated that the clouds were about 500 to 700 feet above the ground with heavy rain in the vicinity. The other passenger of the Cessna, who was a commercial certificated pilot, reported that weather was progressively deteriorating throughout the day of the accident. A few minutes after the DHC-2 departed, he saw the company Cessna overfly his location from the north-northeast. At the time the DHC-2 departed, he estimated that the cloud bases were around 500 to 700 feet above the adjacent mountain ridges. He noted that during the flight to King Salmon around the Cape Douglas area, the airplane encountered moderate turbulence that only lasted a few moments. He said that as the flight continued, in-flight visibility was about 5 miles lateral and that the flight remained at an altitude of about 500 feet agl during the entire portion of the flight due to the cloud ceiling 100 to 200 feet above their altitude. A pilot, who was flying in the vicinity of the Katmai National Park on August 21, reported that he was unable to follow the coastline due to the low cloud ceilings, which were almost to the water along his intended route to the Hallo Bay Camp, which is south of Swikshak Lagoon. The witness said that he flew an alternate course, heading to the north-northwest along the coastline to the Kamishak River, and continued upriver toward Big River. He stated that he intended to fly down the Big River drainage to the Hallo Bay Camp, but as he approached Big River he saw two airplanes, a de havilland DHC-2, painted like that of the accident airplane, and a Cessna 206 flying in trail at an altitude of about 150 to 200 feet agl on a course toward the Hallo Bay Camp. He estimated that in this area, the bottom of the overcast cloud layer was at or below 500 feet agl. Shortly after observing the two airplanes, he decided to do a 180-degree turn, and flew down the Kamishak River drainage, toward Kamishak Bay. Upon arriving at Kamishak Bay, the pilot/witness went along the coastline to the southeast, where he encountered improved weather conditions, and estimated the cloud base to be around 1,300 feet agl. The pilot said that he was able to land at his intended destination around 1340, after which he monitored the weather radar and took a nap before departing ar