Date of Award

8-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Industrial Engineering

Advisor

Shappell, Scott

Committee Member

Gramopadhye , Anand

Committee Member

Cho , Byung R

Committee Member

Wiegmann , Douglas

Abstract

Previous general aviation (GA) accident studies showed that decision errors were more associated with fatal GA accidents than other kinds of human errors, and weather related accidents, especially continued visual flight rules (VFR) flight into instrument meteorological conditions (IMC), remained the major cause of fatal GA accidents. Thus, finding the underlying causes of GA pilots' decision errors and continued VFR flight into adverse weather conditions are needed to reduce weather related GA accidents as well as fatal GA accidents.
Causal factors and hypotheses of weather related GA accidents show that knowledge, experience, motivation, and weather information frequently have been referred as causal factors of weather-related GA accidents. Among causal hypotheses, situation assessment and risk assessment hypotheses have been cited frequently as the causes of weather related GA accidents.
The purpose of this study is to evaluate the effects of weather recognition training on GA pilots' situation assessment and tactical decision making under gradually aggravating weather conditions. To meet this purpose, WeatherWise and an X-Plane 9 flight simulation program has been used. WeatherWise is a computer based weather training program developed by Wiggins et al. (2000) to improve GA pilot weather-related decision making, and was approved by the Federal Aviation Administration (FAA) for free public use.
Pilot situation assessment is a pilot's understanding of a current flight state, and was evaluated in terms of weather assessment and risk assessment. Weather assessment is the pilot's ability to recognize or estimate the changes in visibility, ceiling, and weather condition. Risk assessment is the understanding of the risks associated with flying in adverse weather conditions, and was measured in terms of risk perception and risk tolerance using the Hazardous Event Scale, personal weather minimums, and the Aviation Safety Attitude Scale. Pilot situation assessment was measured by a post experiment questionnaire.
Pilot tactical decision making is in flight judgment, and was evaluated in terms of decision accuracy and decision confidence. Decision accuracy was evaluated by measuring the distance that a pilot has flown from an optimal divert point to an actual divert point, and the distance a pilot has flown into adverse weather conditions. Decision confidence is the pilot's confidence level in making diverting decisions when the pilot encounters adverse weather, and was measured by subjective rating method.
Findings of the study indicated that the WeatherWise training group exhibited significantly higher weather assessment as measured by ceiling estimation ability and decision accuracy as measured by flown distance into adverse weather condition than the control group, but no significant differences were found in their risk assessment and decision confidence. Although the effects of weather training on the risk assessment were not significantly different between the two groups, participants in the WeatherWise training group was more conservative toward flying into adverse weather condition than the control group.
It was hypothesized to find a positive relationship between pilots' situation assessments and their tactical decision-making because situation assessment forms a basis for decision making; however, positive relationship was found only between pilots' ceiling estimation and flown distances into adverse weather in this study. Thus, it can be concluded that the weather training was effective at least in part to pilot situation assessment and tactical decision making. In addition, considering the weather training was just one-time 30 minute training, long-term effects of weather training should be conducted to find further relationship between pilot situation assessment and tactical decision making.
The results of this study can be expanded not only to GA pilots but also to commercial airline pilots and military pilots for various reasons. First, all pilots are expected to acquire weather recognition skills and knowledge to ensure a safe flight regardless of their flight types because the nature of weather condition changes is dynamic and hard to predict during the flight. Second, although those aircrafts are well equipped with navigation aid systems and weather display radar, they do not provide real–time weather information, and they sometimes malfunction.
In conclusion, it is expected that this study will be helpful for GA pilots to understand the effects of weather recognition training on weather decision making, and eventually help them assess a situation correctly and make a timely in–flight decision. It is believed that this study will help to establish a sound foundation for weather training program and has the potential to reduce weather-related GA accidents by implementing weather training during flight training.

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