Accident Overview
On the morning of the accident, a cargo airplane departed Fairbanks International Airport (FAI) at approximately 0955 on a flight to Kobuk Airport (OBU) in Kobuk, Alaska. The aircraft was carrying 3,400 gallons of unleaded fuel and two 100-gallon propane tanks.
Sequence of Events
An eyewitness reported seeing the airplane flying west with the far left engine not running, accompanied by a small white plume of smoke from that engine. The airplane began turning south, at which point the witness noticed the engine was on fire. About three minutes after departure, the pilot informed air traffic control of an onboard fire and initiated a left turn back toward the airport.
Video surveillance captured white smoke developing behind the No. 1 engine, followed by flames. Seconds later, a bright white explosion occurred just behind the No. 1 engine. The airplane entered an uncontrolled, descending left turn and impacted terrain. The No. 1 engine separated from the wing approximately 100 feet above the ground and landed on a frozen river. Approximately two minutes after impact, a large explosion was observed.
Scientific Detection
The University of Alaska Fairbanks (UAF) detected multiple low-frequency sound signals (infrasound) associated with the accident. Analysis of the data indicated the first explosion occurred at 1001, the airplane impacted terrain at 1003, and the second explosion occurred at 1006.
Damage and Injuries
The airplane was totally destroyed by impact forces and a post-crash fire. Both crew members were fatally injured.