The Role of Situation Assessment and Flight Experience in Pilots' Decisions to Continue Visual Flight Rules Flight into Adverse Weather
Wiegmann, Douglas A., Goh, Juliana, O'Hare, David, Human Factors
In an analysis of general aviation (GA) accidents between 1990 and 1997, Goh and Wiegmann (2001a) found that the fatality rate in accidents involving visual flight rules (VFR) flight into instrument meteorological conditions (IMC), or unqualified flight into adverse weather, was consistently higher than that of other GA accidents. The fatality rate for accidents related to VFR flight into IMC was approximately 80% during this period, compared with about 19% for other types of GA accidents. These statistics reflect similar trends found by the National Transportation Safety Board (NTSB, 1989) for U.S. GA accidents that occurred during the 1970s and mid-1980s, as well as GA accident trends in other countries (e.g., United Kingdom and New Zealand). Together these findings clearly indicate that VFR flight into IMC is a major safety hazard in general aviation (O'Hare & Smitheram, 1995).
VFR flight into IMC is often characterized by pilots' decisions to continue a flight into adverse weather conditions despite having been given information or presented with cues indicating they should do otherwise (NTSB, 1989). This continuation of one's original plan, even with the availability of new evidence suggesting that the plan should be abandoned, has been termed a plan continuation event (PCE; Orasanu, Martin, & Davison, 2001). In circumstances when the identified events are considered errors, PCE also stands for plan continuation error.
Plan Continuation Errors
Burian, Orasanu, and Hitt (2000) analyzed 276 aviation incident reports that involved weather events and found that 28% of the 333 identified decision events were considered to be plan continuation errors. The commission of PCEs in these cases was very strongly related to violations of the rules as defined by Reason (1990). In other words, the continuation of a flight into adverse weather was often found to be a willful disregard for the regulations and cues that dictated an alternative and safer course of action. According to the authors, these violations reflect a growing commitment to a chosen course of action, or a tendency to adhere to an original plan, which ultimately interfered with pilots' critical analysis and ability to evaluate the feasibility of the chosen plan over time.
A similar explanation for VFR flight into IMC focuses on predictions made by prospect theory (Kahneman & Tversky, 1982). For example, O'Hare and his colleagues (O'Hare & Owen, 1999; O'Hare & Smitheram, 1995) investigated how pilots frame the situation of continuing or discontinuing a flight into adverse weather. In essence, their hypothesis predicts that pilots who frame diverting from the planned flight as a loss (e.g., loss of time, money, and effort) will tend to continue with the flight, whereas those who frame the diversion as a gain (e.g., in personal safety) will tend to divert. Indeed, O'Hare and Smitheram (1995) found that during a simulated VFR cross-country flight, pilots who were presented with adverse weather information that focused on the gains of diverting were less likely to continue the flight than did pilots who were presented the same weather information that focused on the losses associated with diverting.
O'Hare and Smitheram (1995) suggested that in a real flight environment, decision frames may be induced by the proximity of the pilot's goal, such as the destination airport. As goal achievement gets closer, there may be a natural shift from the gains to the loss frame, resulting in what is known in prospect theory as the sunk-cost effect. Specifically, if more has been invested in a certain course of action, it is less likely that this course of action will be abandoned than if less were invested (Kahneman & Tversky, 1982). O'Hare and Owen (1999) formally tested this hypothesis by requiring pilots to fly a simulated cross-country flight in which they encountered adverse weather either early or late into the flight. …