Human factors

Flying Safety, Jan-Feb, 2008 by Brian T. Musselman

Of the 35 Class A aviation mishaps involving unmanned aerial vehicles and manned aircraft in FY07, 22 were coded with DoD Human Factors Analysis and Classification System (DoD HFACS) codes (these numbers include all aviation mishaps--rate and non-rate producing). Of the 12 mishaps not coded, 5 were bird strikes, 7 were power plant-related and 1 was a mechanical failure. The investigation boards for these mishaps did not identify human factors involved, because they were not evident or present in the mishap. The DoD HFACS was accepted as the DoD Human Factors Taxonomy by the U.S. Armed Services Safety Chiefs in a Memorandum of Agreement (MOA) on 10 May 05. Since this time, the U.S. Air Force has been using this taxonomy for mishap investigation; however, FY07 is the first year this taxonomy was used for all Class A aviation mishaps. The increased benefit of DoD HFACS over the previous legacy human factors taxonomy is that it allows us to look at not just individual human failures, but the failures in the systems that humans design, build, operate, and maintain. DoD HFACS, as opposed to the legacy human factors taxonomy, is organized in a more systemic format which allows easier identification of relationships between factors.

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Looking at the top-level tier of DoD HFACS, Organizational Influences, FY07 saw Procedural Guidance/Publications, Acquisition Policies/Design Processes, and Organizational Training Issues as the highest reported codes. Procedural Guidance/Publications was present in 13 of the 22 coded mishaps (59 percent). Organizational Training Issues was cited in 5 mishaps, and Acquisition Policies/Design Processes was cited in 5 mishaps. Procedure Guidance/Publications was also cited in 4 of the 5 mishaps which cited Organizational Training Issues and 4 of the 5 mishaps which cited Acquisition Policies/Design Processes. For example, one mishap involving a dropped object due to hatch not being closed securely cited the latch design, written procedures for securing the latch, and maintenance training issues as factors in the mishap. These three organizational tier codes each contributed to the mishap; not just one was the exclusive cause of the mishap. Additionally of interest, Procedural Guidance/Publications was cited in 88 of 179 mishaps (50 percent) between FY02 and FY07.

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At the Supervisory tier, no one code was present in a significant number of mishaps. When combining the 5 mishaps which cited Organizational Training Issues/Programs and 2 separate mishaps which cited Local Training Issues/Programs, a total of 6 mishaps cited training issues as a factor in the mishap (one mishap cited both Organizational and Local Training). More telling is Local Training Issues which was cited in 4 mishaps in FY06 and 30 mishaps from FY02 to FY06. On the positive side, the presence of Limited Total Experience and Proficiency in Class A aviation mishaps had been reduced. Limited Total Experience was present in 19 mishaps from FY02 to FY05 and no mishaps in FY06 and FY07. Proficiency was present in 15 mishaps from FY02 to FY05, none in FY06, and 1 mishap in FY07. It is rewarding to see this positive trend.

The Preconditions of Individuals Tier is the most complex tier and includes Environmental Factors, Perceptual Factors, and Conditions of the Individual. These are conditions which should be recognized and managed properly. When they are not managed properly, they are often present in a mishap chain. Cognitive Factors continue to be present in Class A mishaps. In total, Cognitive Factors was present in 11 of the 22 coded mishaps (50 percent). Channelized Attention, Cognitive Task Oversaturation and/or Confusion were present most often. The only relationship identified between the Cognitive Factors was between Channelized Attention and Cognitive Task Oversaturation. Of the 6 mishaps which coded Channelized Attention, Cognitive Task Oversaturation was cited in 3 of these mishaps. Other than the Cognitive Factors, the most prevalent Preconditions codes for FY07 were codes for fatigue and perceptual factors. Fatigue-Physiological/Mental was cited in 4 mishaps, Circadian Rhythm in 3 mishaps, and Inadequate Rest in 2 mishaps. All told, fatigue was present in 5 of the 22 coded mishaps (or 23 percent). A Judgment and/or Decision Making Error was the resultant act in all 5 fatigue-related mishaps. It has long been known that sleep deprivation produces deficits in elementary cognitive processes such as alertness, attention, concentration, and psychomotor vigilance. However, recent interest has been more specifically focused on how sleep loss may affect higher order cognitive processes such as judgment, decision making, and cognitive control. These types of cognitive processes rely heavily on the functional integrity of the prefrontal cortex. Twenty-four hours of continuous sleep deprivation is associated with significant reductions in metabolic activity within the prefrontal cortex. (Aviation, Space and Environmental Medicine, October 2007, Volume 78, Issue 10). Of the Perceptual Factors, Misperception of Operational Conditions was listed in 4 mishaps and Expectancy was listed in 4 mishaps. Of the mishaps which included Misperception of Operational Conditions, 3 resulted in a Judgment and/or Decision Making Error. On the up side, Task Delegation and Mission Planning were not reported in a single mishap in FY06 or FY07; however, they were reported 30 and 14 times respectively from FY02 to FY05.