Visual Experiments Related to Night Carrier Landing

There is a substantially higher incidence of carrier landing accidents at night than during the day. Disasterously low final approaches, a major source of night landing accidents, have been attributed to a visual illusion involving overestimation of altitude. In order to evaluate visual performance in related tasks, subjective judgements of the altitude of a luminous horizontal bar relative to eye level were obtained in total darkness and in the presence of a peripheral artificial horizon. Errors as large as 1° visual angle, corresponding to 8 ft at a range of 500 ft from touchdown, occur frequently, indicating the inadequacy of direct visual contact unaided by artificial display devices. The dramatic reduction in variability resulting from the presence of the artificial horizon demonstrates the importance of a visual frame of reference or structure.