Head-up displays: effects of clutter, display intensity, and display location on pilot performance.Int J Aviat Psychol. 1998; 8(4):377-403.IJ
Two experiments examined the effects of display location (head-up and head-down), display clutter, and display intensity on pilot performance in a general aviation-cruise flight environment. In Experiment 1, a low-fidelity simulation revealed that the detection of commanded flight changes and flight-path tracking performance was better in the head-down condition as compared to the head-up condition. In contrast, midair traffic detection was superior with the head-up display (HUD), reflecting an attentional trade-off. Experiment 2 used the same paradigm in a high-fidelity visual simulation. Flight performance was equivalent between HUD and head-down locations. Detection of commanded changes and traffic was better in the HUD condition, revealing the HUD benefits of reduced scanning. The presence of clutter inhibited detection of command changes and traffic in both head-up and head-down conditions. Lowlighting the task-irrelevant clutter did not facilitate detection of commanded changes, however, the clutter cost for detecting traffic was diminished if the added information was lowlighted in the head-down location. The data suggested that attention was modulated between tasks (flight control and detection), and between display areas (head-up and head-down).