Abstract
The purpose of this paper is to determine how and where pilots watch the observation cues during aircraft landing such as runway, horizon. Furthermore this paper investigates the relative importance of each visual cue available to pilots, the relationship between visual cues and estimation of state variables and how the pilot gain change in order to minimize the state estimation error when some visual cues are lost. It's found that visual cue of the both side edges of the runway are more important than the others in the state estimation in the final approach phase. Furthermore the pilot gain decreases when the important visual cue is lost and increases when the altitude becomes lower.
