The "outside-in" attitude display concept revisited

The "outside-in" attitude display concept, which includes a moving-aircraft (as opposed to a moving-horizon) attitude reference, dates back to the early days of flying. The majority of the laboratory and in-flight studies that have evaluated the outside-in format over the years have found it to be superior at preventing roll-reversal errors during normal flying and in recovering from unusual attitudes. Although outside-in attitude displays have been, and continue to be, flown throughout the world, the majority of military and civilian aircraft have failed to adopt this format. This article reviews the purported advantages and disadvantages of outside-in displays, presents a neuropsychological explanation for their general superiority in maintaining spatial orientation, and describes 3 new situations (off-axis helmet-mounted display viewing, global situation displays, and control of uninhabited aerial vehicles) for which the outside-in concept appears to be ideally suited.