I signed up to write my Night Rating exam on Friday and as part of the learning, one needs to recognise and be aware of optical illusions that can trick a night pilot. This article sums up some of the information I have been reading...
There are many different types of visual illusions that commonly occur at night. Anticipating and staying aware of them is usually the best way to avoid them.
AUTOKINESIS
Autokinesis is caused by staring at a single point of light against a dark background for more than a few seconds. After a few moments, the light appears to move on its own. To prevent this illusion, focus the eyes on objects at varying distances and avoid fixating on one target. Be sure to maintain a normal scan pattern.
FALSE HORIZON
A false horizon can occur when the natural horizon is obscured or not readily apparent. It can be generated by confusing bright stars and city lights. It can also occur while flying toward the shore of an ocean or a large lake. Because of the relative darkness of the water, the lights along the shoreline can be mistaken for stars in the sky.
NIGHT LANDING ILLUSIONS
Landing illusions occur in many forms. Above featureless terrain at night, there is a natural tendency to fly a lower-than-normal approach. Elements that cause any type of visual obscuration, such as rain, haze, or a dark runway environment also can cause low approaches. Bright lights, steep surrounding terrain, and a wide runway can produce the illusion of being too low, with a tendency to fly a higher-than-normal approach.
Often a set of regularly spaced lights along a road or highway can appear to be runway lights. Pilots have even mistaken the lights on moving trains as runway or approach lights. Bright runway or approach lighting systems can create the illusion that the airplane is closer to the runway, especially where few lights illuminate the surrounding terrain.
and off another site, some more information here...
Empty Visual Field “Blindness”:
This situation occurs when the eye is not simulated and encouraged to re-focus. The eye will transition to a resting focus of 3-4 metres. To avoid this maintain a scan that periodically involves close objects (the instrument panel) and further points (the wing tip and further afield) (Ewing, 1993). This illusion can also occur during the day in cloud, hazy conditions and over vast, featureless areas such as snowfields, deserts and water.
Break-off Phenomenon:
Is reported to occur during flight in areas of low visual stimulus, often with a low workload, including at night (Ewing, 1993). Ewing (1993) states that solo pilots note a feeling of detachment and floating free of the aircraft, or that the aircraft feels like it is balancing on a knife edge, about to fall off. This feeling is short lived, and pilots who are more anxious than average may be more susceptible and it is relatively common in situations of low visual stimulus (Ewing, 1993).
Black Hole Effect:
A common situation that is especially prone to developing when on a long straight in approach over the sea or unlit terrain, Black Hole Effect is something all pilots should be aware of. One strategy for dealing with black-hole approaches is to use the VASI or ILS
glideslope to maintain a safe altitude on approach, though not all airports have
these. However, with the wide availability of GPS (or DME when there's a VOR on
the field), you can approximate your own three-degree slope. On a three-degree
glideslope, you'll descend 318 feet for each nautical mile you travel. So while
on approach, stay at least this high above the ground for every mile away from
the runway. In any case, avoid very long, straight-in approaches at night,
particularly if no glideslope guidance is available.
I have also compiled my own Training Manual for a Night Rating and you can download it fee here... click on the link.
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