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 that the highest percentage of the unmonitored/unchallenged errors were tactical decision errors (40 percent).

In addition, the study found that, of the 15 accidents for which information was available, 11 (73 percent) occurred during the first duty day together for the captain and first officer. Of the 16 accidents for which data were available, 7 (44 percent) occurred during the crewmembers' first flight together. According to the study, these rates are substantially higher than the percentage of crews who would be expected to be paired for the first time on any given flight or day.

Finally, the study examined the effect of the length of time since awakening (TSA) on the errors committed by flight crewmembers in the accident sequence. The performances of flight crews in which both the captain and the first officer had been awake a long time (average TSA length, 13.6 hours) were compared with flight crews in which both the captain and the first officer had been awake a short time (average TSA length, 5.3 hours). The Safety Board found that both the number and type of errors made by the flight crews varied significantly according to the TSA length. Specifically, high TSA crews made an average of 40 percent more errors (almost all of which were errors of omission) than low TSA crews.

High TSA crews made significantly more procedural errors and tactical decision errors than low TSA crews. These results suggested that the degraded performance by high TSA crews tended to involve ineffective decision-making (such as failing to perform a missed approach) and procedural slips (such as not making altitude awareness callouts) rather than a deterioration of aircraft handling skill. Also, the number and types of errors made by the flight crews varied according to the TSA length before the accident. The median TSA periods were quite high: 12 hours for captains and 11 hours for first officers. Those pilots who had been awake longer than the median TSA length for their crew position made more decision-making errors and procedural errors than pilots who had been awake for less time.

1.18.5.2 Previous Safety Recommendations on Flight Crew Decision-making

On the basis of the findings of its safety study, the Safety Board issued Safety Recommendations A-94-3 and A-94-4 on February 3, 1994. Safety Recommendation A-94-3 asked the FAA to

Require U.S. air carriers operating under 14 CFR Part 121 to provide, for flight crews not covered by the Advanced Qualification Program, line operational simulation training during each initial or upgrade qualification into the flight engineer, first officer, and captain position that (1) allows flight crews to practice, under realistic conditions, nonflying pilot functions, including monitoring and challenging errors made by other crewmembers; (2) attunes flight crews to the }}