Fairbanks

The purpose of the flight was to transport 3,400 gallons of unleaded fuel and two 100-gallon propane tanks from Fairbanks International Airport (FAI), to Kobuk Airport (OBU), Kobuk, Alaska. The airplane departed about 0955. An eyewitness reported seeing the airplane flying to the west and stated that the far left engine was not running. They also noticed a small, white plume of smoke coming from that engine. The airplane started to turn to the south, and at that point he noticed that the engine was on fire. About three minutes after departure, the pilot reported to air traffic control that there was a fire onboard and began a left turn back to the airport. Video surveillance showed white smoke begin to develop behind the No. 1 engine, followed by flames. Seconds later, a bright white explosion could be seen just behind the No. 1 engine. The airplane then entered an uncontrolled, descending left turn into terrain. The No. 1 engine separated from the wing about 100 ft above the ground and landed on a frozen river. About two minutes later, the video showed a large explosion. The University of Alaska Fairbanks (UAF) detected multiple low frequency sound (infrasound) signals associated with the accident. Based on the data collected by UAF, the first explosion was at 1001, the airplane impacted terrain at 1003, and the second explosion was at 1006. The airplane was totally destroyed by impact forces and a post crash fire and both crew members were fatally injured.

The flight crew was landing the transport-category airplane at a remote, gravel-covered runway. According to the captain, the terrain on the approach to the runway sloped down toward the approach end, which positioned the airplane close to terrain during the final stages of the approach. A video recorded by a bystander showed that while the airplane was on short final approach, it flew low on the glidepath and dragged its landing gear through vegetation near the approach end of the runway. The video showed that, just before the main landing gear wheels reached the runway threshold, the right main landing wheel impacted a dirt and rock berm. The captain said that to keep the airplane from veering to the right, he placed the No. 1 and No. 2 engine propellers in reverse pitch. The flight engineer applied asymmetric reverse thrust to help correct for the right turning tendency, and the airplane tracked straight for about 2,000 ft. The video then showed that the right main landing gear assembly separated, and the airplane continued straight down the runway before veering to the right, exiting the runway, and spinning about 180°, resulting in substantial damage to the fuselage. On-site examination of the runway revealed several 4-ft piles of rocks and dirt at the runway threshold, which is likely what the right main landing wheel impacted. Given that the airplane landing gear struck vegetation and rocks on the approach to the runway, it is likely that they were below the proper glidepath for the approach. The crew stated there were no preaccident mechanical malfunctions or anomalies that would have precluded normal operation.

The pilot reported that, following a precautionary shutdown of the No. 2 engine, he diverted to an alternate airport that was closer than the original destination. During the landing in tailwind conditions, the airplane touched down "a little fast." The pilot added that, as the brakes faded from continuous use, the airplane was unable to stop, and it overran the end of the runway, which resulted in substantial damage to the fuselage. The pilot reported that there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation.