What optical cues do pilots use to initiate the landing flare? Results of a piloted simulator experiment

A piloted moving-base simulator study of the landing of a twin-engined executive jet airplane was conducted to find out if pilots also use an optical variable called the Time-To-Contact (TTC) or tau, to time their actions. By manipulating the approach-path angle and the visual speed of the visible runway outline, the influence of the perceived TTC on the initiation of the landing was assessed. Results suggest that pilots indeed use some kind of Tau-margin strategy, but rely on the judgement of absolute height as well. Further experiments are needed to rule out any influence of prior training on the timing of the flare. Recent work on timing and perception suggests that the amplitude or speed of control actions may be determined by a higher order variable, i.e. the perceived rate of change of the Time-To-Contact, called Tau-dot. Possible implications of this for furthther work are mentioned.