INTRODUCTION: The benefits of using head-up displays (HUDs) include reducing head-down time during critical flight phases, enhancing awareness of the external environment, and improving in-flight crew performance. However, the monochromatic nature of HUDs, increased head rotation, and longer gaze movement paths might affect pilots’ reactions to different types of alerts.

METHODS: Pilot workload and behavior differences were examined between HUD and head-down display (HDD) configurations in three alert scenarios. The study was carried out in an A320 flight simulator and 12 pilots participated.

RESULTS: Except for one engine-on-fire scenario, pilot workload when using a HUD was significantly lower than using an HDD. In one engine-on-fire (3.98 s vs. 3.57 s) and one gear-disagree (5.42 s vs. 4.69 s) scenario, pilot response time to alerts using HUD was significantly longer than using an HDD. The angle deviations were significantly smaller when using HUDs in both go-around-under-crosswind (2.67° vs. 3.37°) and one engine-on-fire scenario (1.22° vs. 1.89°).

DISCUSSION: The HUD is suitable for a lengthy process of manual flight control inputs, which not only reduces workload but also promotes control accuracy. For tasks that rely on automation, the benefits for workload become less obvious. In addition, head rotation and reorientation of attention adversely affected the response time to non-time-critical warnings and cautions. For instantaneous control with high precision requirements, HUDs did not demonstrate a significant advantage.

Zheng Y, Lu Y, Jie Y, Fu S. Pilots’ reactions to different types of alerts when using head-up displays. Aerosp Med Hum Perform. 2024; 95(9):688–694.