One cue for visual judgment of glidepath angle has been referred to as form ratio. Form ratio is defined as the ratio of vertical height of the runway to width of the far end in the runway retinal image. The ability of pilots to judge form ratios was compared with the ability to judge approach angles in the nighttime 'black hole' situation in two experiments.
In one experiment, 16 pilots observed a stationary model of a lighted airport runway under nighttime conditions at different simulated approach angles from a simulated distance of 8,000 ft from threshold. Pilots made verbal judgments of approach angle using the categories 'low,' 'high,' and 'OK,' and on half the trials also estimated form ratios.
In the second experiment, 20 pilots made observations both in a similar static condition at simulated distances of 8,000 ft and 26,000 ft from threshold, and in a dynamic condition in which they controlled the model to produce (i) specified values of form ratio (1.0, 2.0, and 3.0) or (ii) a 3 deg approach angle, as the model approached them between 8,000 and 26,000 ft. The simulated approach speed was 125 knots. Responses in both static and dynamic conditions indicated a general tendency to over-estimate form ratios and approach angles less than 3 deg. Intersubject and intrasubject variability of form ratio and approach angle responses were comparable.
At night, reduced visual cues may promote illusions and a dangerous tendency for pilots to fly low during approaches to landing. Relative motion paral...
Previous experiments have demonstrated illusions due to variations in both length and width of runways in nighttime 'black hole' approaches. Even thou...
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