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A jumbled conversation followed in which both the first officer and the f light engineer quickly identified that the engine was fuel starved. Within 30 seconds of the initial failure, a second engine on the same wing flamed out. Both engines fed from the same fuel tank. The crew began cross-feeding and were able to relight the two en- gines via the opposite wing fuel supply, but within a few minutes that tank was empty as well. All four engines flamed out in quick succession.
The captain appeared to be genu- inely puzzled when the first engine failed. It is clear that he did not im- mediately correlate the failure to a dangerously low quantity of fuel on- board. The f light engineer also ex- pressed surprise but was quicker at
faulted the captain for failing to maintain situational awareness, and the first officer and f light engineer for failing to directly challenge the captain’s decision-making process.
A New Understanding of Error
Threats are encountered on every f light. They mostly represent condi- tions that cannot be changed. Errors are the result of inappropriate actions taken by pilots. The longstanding at- tempt to eliminate pilot error in avia- tion has proven an elusive goal. A bet- ter strategy is to focus on minimizing the impact of errors when they occur. Trapping an error is nearly as good as avoiding one. Under this model, the dif- ference between a threat and an error is largely procedural. A landing gear malfunction during final approach (for example) represents a threat. In the case of United 173, another threat was the hierarchy that existed among the flight crew. The captain possessed an extraordinary amount of experience. It is understandable why the first officer and flight engineer would have been reluctant to directly challenge him. The captain failed to actively include the first officer and flight engineer in his decision-making process, which represented an error.
Communication with ATC was likewise inadequate, another error. Plenty of resources were available to the captain, yet he failed to trigger them effectively. His loss of situational awareness regarding fuel endurance was the final nail in the coffin. It is worth noting that many of his errors resulted from his singular focus on a necessary event: Ensuring that the passengers were briefed should an evacuation become necessary.
The problem was not that errors oc- curred but that the crew failed to trap them. The abnormal gear procedure on the DC-8 directed the crew to ex- ecute a normal approach in the event that the gear indicators on the wing were extended, which they were. The first officer never directly challenged the captain regarding diminishing fuel reserves even though the subject was clearly on his mind. The flight engineer noted that insufficient fuel remained for another turn in the hold, yet the captain failed to consider his
concern. The crew did not explicitly declare an emergency until all four engines had flamed out. For the initial 45-minutes of the event, the only thing that ATC had to go on was: “We’ve got a gear problem. We’ll let you know.”
The first indication that the landing would be abnormal was when the cap- tain requested crash and fire rescue “in the event [it] should become neces- sary.” Controllers initiated emergency procedures following the exchange. This occurred 12 minutes prior to the crash. Even after the initial two en- gines had flamed out, the crew failed to inform ATC of their dire status. Instead, they coyly requested “clear- ance for an approach into two eight left, now.” The abnormal gear checklist that began the ordeal had only taken 15-minutes to complete. The remain- ing 40 minutes of follow-on activity generated sufficient error, omission, fixation, and poor communication to produce a fatal accident.
Threat and Error Management
The NTSB recommended aircrew “assertiveness” training as a result. This rapidly morphed into what we now call Crew Resource Management (CRM). It would initially focus on en- hancing the “challenge-response” dy- namic among flight crew. It did not take long before the umbrella of CRM expanded to include resources outside of the flight deck as well: ATC, passen- gers, flight attendants, maintenance workers, and any other of a slew of supporting personnel who contribute to safe flight. Single-Pilot Resource Management (SRM) naturally arose from the realization that every pilot has a multitude of external resources available to assist in decision-making.
It is important to distinguish be- tween “single-pilot” and “single-oc- cupant.” Having a second individual onboard – even if they have little knowledge of aviation – can represent a profound resource. Briefing a pas- senger not only helps to put them at ease but also forces us to utilize a part of our brain that naturally critiques our own impulse. Even a highly ex- perienced pilot sometimes overlooks relevant information. Communication is an effective way to trap those errors.
recognizing the root cause. The first officer immediately suggested that the engine was fuel-starved, clearly indicating that he had been aware of the dwindling fuel supply prior to the flameout. Yet instead of directly chal- lenging the captain on the decision to delay a landing attempt, he instead resorted to questioning the f light engi- neer about the fuel status. Most likely he was hoping that the captain and f light engineer would catch the hint and develop a game plan. The NTSB
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