Engineers Find Way to Lower Risk of Midair Collisions for Small Aircraft

At issue are “cockpit displays of traffic information” (CDTIs). These are GPS displays used by private pilots to track other aircraft in their vicinity. However, pilots often focus on the closest aircraft on the display – a habit that can pose a significant hazard.

If the pilot of Plane A sees two planes on the CDTI, he’s more likely to focus on the closest aircraft (Plane B). But if the more distant plane (Plane C) is moving at high speed, it could cross his path before Plane B does. Not paying enough attention to Plane C increases risk of a midair collision.

“Our goal was to modify a CDTI to help pilots recognize which other planes pose the greatest risk,” says Carl Pankok, lead author of a study on the work and a Ph.D. student in the Edward P. Fitts Department of Industrial and Systems Engineering at NC State. “And it worked.”

Researchers modified the CDTI so that the plane that would cross a pilot’s path first either began blinking or was colored yellow.

The researchers tested the modified CDTI in a flight simulator with a panel of licensed recreational pilots. The research team compared the pilots’ response times and decision-making accuracy when using the modified and unmodified displays.

“These pilots were already pretty good, but the modified CDTIs made them better,” Pankok says. “Their percentage of ‘correct’ decisions – minimizing risk – jumped from 88 percent to 96 percent. And their response times in scenarios where the farther aircraft was the higher-risk aircraft were cut in half; from 7.2 seconds to 3.7 seconds for blinking CDTIs, and to 4 seconds for yellow CDTIs.

“We’re not trying to make money off this,” Pankok says. “We’re hoping that CDTI manufacturers can incorporate these changes and possibly save lives.”

The paper, “Cockpit Displays of Traffic Information and Pilot Bias in Time-to-Contact Judgments,” is published in the June issue of Aviation, Space, and Environmental Medicine. Senior author of the paper is Dr. David Kaber, a professor in the Edward P. Fitts Department of Industrial and Systems Engineering at NC State. The work was supported by the U.S. National Institute for Occupational Safety and Health under grant No.2 T42 OH008673-08.

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Note to Editors: The study abstract follows.

“Cockpit Displays of Traffic Information and Pilot Bias in Time-to-Contact Judgments”

Authors: Carl Pankok, Jr. and David B. Kaber, North Carolina State University

Published: June 2014, Aviation, Space, and Environmental Medicine

Abstract: Introduction: Pilots are susceptible to over-reliance on distance when making relative time-to-contact (TTC) judgments of surrounding intruders, referred to as “the distance bias.” We tested the effect of adding perceptual cues and an information feature to cockpit displays of traffic information to mitigate this bias. Method: Fourteen general aviation pilots participated in a simulated flight scenario and were asked to make relative TTC judgments. Three levels of perceptual cue (blinking, color-change, and no-cue) were crossed with two levels of velocity data tag (present and absent) with identification of the highest risk intruder as a response. Results: Perceptual cues were associated with more accurate high-risk intruder selection (color=95.95% correct, blinking= 95.98%, no-cue=87.89%), decreased response time (color=3.68 sec, blinking= 3.19 sec no-cue=6.08 sec), reduced visual attention demand (color=57% of attention, blinking= 58%, no-cue=62%), lower workload ratings (color=28.38/100, blinking= 29.66/100, no-cue=48.91/100), and higher performance confidence ratings (color=83.92/100, blinking=82.71/100, no-cue=58.85/100) than the no-cue displays. There was no difference between blinking and color cue displays. The data tag was associated with lower response times (present=4.13 sec, absent=4.50 sec) and higher confidence ratings (present=78.69/100, absent=71.63/100) than displays without. Displays including the blinking cue, color-change cue, and data tag were preferred over displays that did not include these features (color=8 pilots, blinking=6, no-cue=0). Discussion: The added display features were effective in mitigating the effect of the distance bias on pilot performance measures and received favorable subjective ratings.