FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-15/9

Title and Subtitle: Pilots' Risk Perception and Risk Tolerance Using Graphical Risk-Proxy Gradients

Report Date: May 2015

Authors: Knecht WR, Frazier E

Abstract: Graphical weather displays such as Next-Generation Radar (NEXRAD) radar reflectivity maps are now extensively being used by general aviation (GA) pilots. Human factors issues associated with such risk-proxy displays are of great interest to researchers, aviation policymakers, manufacturers, and aircraft insurers alike.

To that end, this study is a simple, three-page test of risk tolerance. With risk defined as the chance of "significant damage to your aircraft," and motivation as "fuel cost combined with time pressure," three graphical NEXRAD-like risk gradients were created, each with a different starting value, and logarithmically color-coded with eight different levels of risk posed by potential weather. Each risk gradient was given two different motivation levels. The study utilized 30 GA pilots to draw six flight paths from a departure point to a destination point and estimated each pilot's risk tolerance for each flight, based on flight path length (an efficiency measure) and the highest-risk area traversed (a safety measure).

Three major quantitative findings emerged. First, higher motivation generally led to shorter flight paths, but at the cost of higher risk. Second, in more than half the flights tested here, pilots appeared to exhibit risk tolerances in excess of formal national policy goals. Third, however, the numerical risk values themselves appeared confusing to many pilots.

All three of these findings could be effectively and easily addressed by training.

This study explores plausible theoretical explanations for these findings, including pilots' use of risk heuristics-simplifying mental rules, which substitute for complex mental calculations. Some of these heuristics could benefit from training. The remainder need only be "tuned" to meet policy goals. Finally, the study recommends that the color schemes in flightdeck displays be kept simple and consistent with color schemes pilots already know.

Key Words: General Aviation, Cockpit Displays, Weather Displays, NEXRAD, Risk Perception, Risk Tolerance, Training, Heuristics

No. of Pages: 33