Investigation Summary
The investigation into Flight 608 initially struggled due to the total destruction of the airframe. However, just three weeks later, an American Airlines DC-6 experienced a near-identical fire over Gallup, New Mexico, but managed to land safely. By examining the surviving Gallup aircraft, investigators discovered a critical design flaw: the intake scoop for the cabin heater was located just 10 feet aft of the No. 3 alternate fuel tank vent. During fuel transfers, if a tank was overfilled, gasoline would vent out and be immediately ingested by the heater scoop. In the case of Flight 608, the resulting fire ignited emergency flares stored in the wing fillet and eventually burned through the right wing and tail control surfaces, rendering the aircraft uncontrollable moments before it could reach the Bryce Canyon airstrip.
Final Conclusions
The Civil Aeronautics Board (CAB) determined the primary cause was the combustion of gasoline that entered the cabin heater air intake scoop due to an inadvertent fuel overflow. The board cited the manufacturer (Douglas) and the Civil Aeronautics Administration (CAA) for failing to exercise sufficient caution in the design and analysis of the fuel system, specifically the hazardous placement of fuel vents relative to air intakes. Inadequate crew training regarding fuel management procedures for the new DC-6 type was also noted as a contributing factor.
Photographic Evidence (1)
Video Analysis
Setting Yourself On Fire | United Airlines Flight 608 — A detailed look at the design flaw that caused the first DC-6 crash and the subsequent grounding of the entire fleet.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Captain Everett L. McMillen
First Officer
Systems & Failure Modes
Cabin Heater Intake
Located on the fuselage near the wing fillet, it inadvertently sucked in vented fuel from the alternate tanks.
Fuel Vent System
The No. 3 alternate tank vent was positioned too close to the heater intake, allowing slipstreamed fuel to enter the heater duct.
Emergency Flares
Magnesium flares stored in the trailing edge of the wing fillet ignited during the fire, accelerating structural failure.
Interesting Facts
- 01It was the first crash involving a Douglas DC-6 aircraft.
- 02The fire was so intense that it ignited magnesium emergency flares located in the wing fillet.
- 03The wreckage was loaded onto trucks and transported to the Douglas factory in California to be reassembled for study.
- 04Jeff Burkett, a punter for the Chicago Cardinals NFL team, was among the fatalities.
- 05The crash site was located on National Park Service land within Bryce Canyon.
Safety Actions & Advisories
DC-6 Fleet Grounding
The entire fleet of 80 Douglas DC-6 aircraft, including the U.S. President's aircraft 'The Independence', was grounded for modifications.
Design Modification
The fuel tank vents were relocated and the cabin heater intake was redesigned to prevent the ingestion of vented fuel.