Investigation Summary
The investigation revealed a chain of maintenance failures that turned a routine engine failure into a catastrophic loss of control. The number one engine had been replaced twice in the two weeks preceding the accident, most recently with an overhauled unit just one week prior. During this maintenance, a B-nut fitting on the propeller feathering system bulkhead was left unattached to its corresponding oil hose. Additionally, the outboard left fuel tank had a known leak that a repair attempt the day before the accident failed to rectify. The tank leaked at a rate of 5 to 10 drops per minute when full, allowing fuel to pool in the wing space behind the engine. When the engine failed for undetermined reasons during the initial climb, the pilots followed standard procedure to feather the propeller to reduce drag. Activating the feathering pump forced high-pressure oil through the disconnected fitting, spraying it directly onto the exhaust system. The resulting oil fire ignited the accumulated fuel in the wing, triggering an explosion that destroyed the flight control linkages (specifically the aileron bell housing). This caused the aircraft to enter a sharp left turn of over 90 degrees and an uncontrolled descent. The number one engine physically separated from the airframe approximately 100 feet above the ground just before impact.
Final Conclusions
The NTSB determined the probable cause was the loss of power in the No. 1 engine for undetermined reasons, combined with the incorrect installation of a B-nut fitting in the propeller feathering system. This maintenance error allowed engine oil to spray onto the exhaust system during the feathering attempt, causing a fire. A contributing factor was an incorrectly repaired fuel leak in the outboard left fuel tank, which resulted in a fuel explosion that separated the aileron bell housing, causing a loss of control. The final report was released in April 2025 (NTSB ANC24FA029).
Video Analysis
N3054V DC-4 Alaska Crash 23 April, 2024 — Analysis of the Alaska Air Fuel DC-4 crash near Fairbanks, including eyewitness footage of the in-flight explosion and a review of the aircraft's history as a former aerial firefighter.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Also the owner of Alaska Air Fuel.
Co-pilot
Systems & Failure Modes
Propeller Feathering System
Uses a dedicated pump to force high-pressure oil to the propeller hub to rotate blades to a low-drag position. A disconnected B-nut at the firewall bulkhead caused this oil to spray onto the exhaust.
Aileron Control Linkage
The aileron bell housing, located near the No. 1 engine, was destroyed by the in-flight explosion, causing a total loss of lateral control.
Fuel Cargo System
The aircraft was configured to carry 3,400 gallons of unleaded fuel in internal tanks for delivery to remote villages.
Interesting Facts
- 01The aircraft was a 1945-built military C-54D that had previously served as an aerial firefighter (Tanker 16).
- 02The No. 1 engine had been replaced with an overhauled unit just seven days before the accident.
- 03A known fuel leak in the outboard wing tank was dripping 5 to 10 drops per minute into the wing space behind the engine.
- 04Post-crash examination found a B-nut fitting in the propeller feathering system was not attached to its hose.
- 05The in-flight explosion was powerful enough to separate the aileron bell housing, rendering the aircraft uncontrollable.
Safety Actions & Advisories
Wreckage Recovery
Source ↗The NTSB coordinated with the operator's insurance company to remove the wreckage from the sensitive riverbank location on June 13 and 14, 2024, to prevent further environmental contamination and facilitate detailed examination.
Known Controversies & Unanswered Questions
Environmental Cleanup Decision
Reference ↗The Alaska Department of Environmental Conservation (ADEC) faced scrutiny for its decision not to conduct a formal cleanup of the crash site. ADEC cited the low remaining fuel volume (most was consumed by fire) and the extreme difficulty of the terrain, despite the crash occurring on the banks of the Tanana River.