featureless terrain illusion

featureless terrain illusion

An optical illusion caused by the absence of ground features, such as when landing over water, darkened areas, and terrain made featureless by snow. The pilot believes that the aircraft is at a higher altitude than it actually is and, in the process, tends to fly a lower approach. The pilot should exercise extra caution in these circumstances. If available, aids like VASI (visual approach slope indicator) should be used to assess the glide path correctly.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved