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What is the greatest potential threat for VFR navigation at night?
  • A
    When external lighting provides good visual cues, flying by cross-reference to instruments may cause spatial disorientation.
  • B
    Exposure to red light can cause the eyes to lose dark adaptation and may cause temporary blindness.
  • C
    The aircraft height during an approach can be easily misjudged due to insufficient external visual cues.
  • D
    It is difficult to determine the flight direction of other aircraft unless their landing lights are on.

Night flying is slightly different to daytime navigation. The pilot can see illuminated objects only, thus there is a danger of flying into terrain in the case of being lost. The so called “black-hole effect” also influences judgement, particularly distance estimation.

The black hole illusion occurs when flying over featureless terrain, approaching an airfield at night over water, jungle or desert. This illusion might fool the pilots into thinking they are higher than they actually are, causing them to fly dangerously low approaches - the aircraft may touch down short of the runway.


"Exposure to red light can cause the eyes to lose dark adaptation and may cause temporary blindness." Incorrect.

  • Rod cells, which allow you to see at night, incorporate a light-sensitive protein - rhodopsin. Red light breaks down rhodopsin more slowly.
"It is difficult to determine the flight direction of other aircraft unless their landing lights are on." Incorrect.
  • Navigation lights aid the determination of the flight direction of other traffic.
"When external lighting provides good visual cues, flying by cross-reference to instruments may cause spatial disorientation." Incorrect.
  • Especially at night, cross-checking the flight instruments is extremely important.

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