What happened
On a scheduled flight from Denver to Portland, United Airlines Flight 173, operating a DC-8-61, experienced a mechanical issue during its descent. While descending through approximately 8,000 feet, the crew attempted to extend the landing gear. This action was accompanied by an unusual noise and a yaw in the aircraft. The crew subsequently notified Portland Approach of a gear problem and entered a holding pattern south and east of the airport.
During the period spent orbiting, the flight crew focused on troubleshooting the landing gear and preparing the cabin for a potential emergency landing. While the second officer verified the gear position visually, the crew engaged in discussions regarding passenger evacuation procedures and crash landing preparations. As time passed, the aircraft's fuel levels dropped significantly. Despite various communications with maintenance personnel and air traffic control, the critical depletion of fuel went unaddressed as the primary focus remained on the gear malfunction.
At approximately 18:06, the crew began noticing engine issues, specifically noting the loss of engine number four due to lack of fuel. Shortly thereafter, additional engines began to flame out. By 18:13, the flight engineer reported that engines one and two had also failed, leading the pilot to declare a mayday as it became clear the aircraft could not reach the airport. At approximately 18:15, the aircraft impacted a wooded area in a populated suburb of Portland. The accident resulted in 10 fatalities (including two crew members and eight passengers) and 34 injuries.
Findings
Investigations determined that the primary cause was the captain's failure to monitor the fuel state and respond to warnings regarding low fuel levels. This lack of oversight was due to a preoccupation with diagnosing the landing gear issue and managing emergency preparations. The investigation also noted that the other crew members failed to effectively communicate the severity of the fuel situation to the captain. It was concluded that all engines failed because of fuel exhaustion, an event that was considered predictable had the crew properly reconciled remaining fuel with the time and distance required for arrival.