Background
Flight 302 departed Iliamna at 1419 local time carrying 11 passengers and 2 crew members. The aircraft was cleared to operate under instrument flight rules (IFR) to Anchorage via low frequency airways: Red Airway 99 (Red 99) to Kakon Intersection, then Green Airway 8 (Green 8) to Anchorage, maintaining an altitude of 7,000 ft.
Flight and Communications
At 1425:20, the flight crew established radio contact with Anchorage Air Route Traffic Control Center's (Anchorage Center) D2 nonradar sector controller. They reported being level at 7,000 ft and estimated arrival at Kakon Intersection at 1434. At 1428:35, Anchorage Center requested the flight's estimate for Homer, Alaska; the crew responded with an estimate of 1515.
The crew did not report passing Kakon Intersection. At 1439:40, they requested permission to file Green 8 and intercept the 192° bearing from Wildwood. Anchorage Center cleared the new route and instructed them to remain at 7,000 ft. At 1440:50, the crew advised an estimate for Clams at 1515. Anchorage Center acknowledged, and this was the last known transmission from Flight 302.
At 1452:08, three abrupt audible sounds were recorded on the Anchorage Center tape of incoming air-to-ground communications from Flight 302. These sounds resembled those produced by the aircraft's radio transmitter during earlier communications. Despite multiple attempts by air traffic control facilities between Iliamna and Anchorage to contact the flight, and the absence of radar returns in areas with coverage, Anchorage Center initiated alert procedures for a possible aircraft accident.
Accident and Aftermath
U.S. Air Force search and rescue aircraft located the wreckage site at 1643 on September 7, 1977. The aircraft had struck a glacier face on the southwest side of Mount Iliamna at an elevation of 7,000 ft. There were no survivors. Due to rapidly changing environmental conditions on the glacier face, recovery of bodies and wreckage was not possible.
Probable Cause
The National Transportation Safety Board determined that the probable cause of the accident was the failure of the flightcrew to use proper navigational procedures for the route to be flown, especially their failure to use the available backup means of navigation to verify the position and the progress of the flight.