What does this mean? SD can afflict any pilot, regardless of experience. It is particularly common among those who are not fully trained to fly to IFR standards or those whose skills may be rusty from non-use. Pilots flying at night or in poor visibility conditions are at an increased risk. Visual illusions, such as the black-hole approach or false horizon effects, can strongly contribute to SD by providing misleading cues that contradict the aircraft's instruments and lead to pilots questioning if the instrument is malfunctioning or their minds are playing tricks on them.