Visual Illusions

Question 1

The sensory inputs that provide orientation and equilibrium are?

Answer 1

• Visual (80%)
• Vestibular (10%)
• Proprioceptive systems (10%)

Question 2

What causes visual illusions?

Answer 2

Perception of brain is inaccurate

Question 3

What are some visual illusions?

Answer 3

Environment (aerial) illusions
Fales horizon
Ground lights
Relative motion
Structural illusions
Height depth perception illusion
Black hole illusion 
Illusions during landing (runway length, runway width)

Question 4

What is environmental (aerial) illusion?

Answer 4

• Objects seen in less detail are perceived as further away than clearly visible
• If haze is present in atmosphere, less detail is visible and therefore the distance may be overestimated
• If two aircraft are same distance away but sizes differ, the larger that can be seen in more detail will normally be judged closer.

Question 5

What is false horizon illusion?

Answer 5

• Occurs when the aviator confuses cloud formations with the horizon or ground.
• This illusion occurs if aviator looks outside after given prolonged attention a task in cockpit

Question 6

What is ground lights illusion?

Answer 6

• Flying to a runway with very bright lights will give the impression that you are close to a runway. Resulting in flying a low approach
• Flying to a runway with dim lights will give the impression that you are further to the runway. Resulting in a high approach with the risk of landing deep (overshoot). Not good if run way short
• Judging the flare will also be affected by ground lights, bright lights will make pilots underestimate his height causing him to flare early and dim lights will cause him to over estimate his flight causing him to flare late or not at all.

Question 7

What is relative motion illusion?

Answer 7

Relative motion is the false perceived self-motion in relation to the motion of another object.

Question 8

What is structural illusion?

Answer 8

Structural illusions are caused by heat, rain, snow, sleet or others

Question 9

What is an example of structural illusion?

Answer 9

• A straight line may appear curved when viewed through heat waves
• With water on the windscreen the pilot will have the impression that the runway moved lower and further away to the aircraft. With water on the windscreen the refraction is much more, and the runway appears to move lower and further away to the aircraft, potentially resulting in a low approach.

Question 10

What is an example of relative motion illusion?

Answer 10

• A pilot taxiing through flog can give the perceived notion that he is speeding, this can result in a pilot slowing down to a standstill while still believing they are still moving
• Flying an approach through driving rain can give the illusion of excessive speed, this may cause the pilot to reduce his speed below safe limits.

Question 11

What is height-depth perception?

Answer 11

This occurs when there is a light of visual cues resulting in the crew to believing they are higher than they actually are
Flying over an area with no visual references, such as desert, snow, or water will deprive the pilot of his perception of height.
Flying over an area, with haze, fog, smoke, or haze products can give height-depth perception illusion.

Question 12

What is black hole illusion?

Answer 12

This illusion happens at mostly at night time where there is cloud obscuring the stars and the horizon, over water or featureless terrain into a brightly lit runway creates the illusion that the aircraft is high. This can result in an under approach situation where the aircraft lands short of runway.

Question 13

What is an example of black hole illusion?

Answer 13

Night approach over water – water looks black – end up with black hole illusion so end up with low approach

White out (happens mostly in polar regions where the snow blends with the sky etc)– you won’t see ground, world will be 2d – you end up with low approach

Question 14

What is autokinesis illusion?

Answer 14

This illusion results when a static light appears to move when it is stared at for several seconds.

To cure this illusion, maintain a normal varying scan pattern.

Question 15

What is runway slope illusion?

Answer 15

This illusion occurs when the runway and ground are not even.

• Nil sloping runway & terrain
• Runway sloping down
• Runway sloping up
• Terrain sloping down from threshold
• Terrain sloping up from the threshold

Question 16

What is runway width illusion?

Answer 16

A pilot may falsely perceive an unfamiliar landing zone to be the same size as to which he is used to landing.

(300x800) Think too low end up high approach
(75x8000) You think you are too high, so you push your nose down and end up with low approach

Question 17

How do you know that the touch down point is correct?

Answer 17

When all the textures from the runway “flow away” from that point. (As aircraft gets closer to ground, the size of everything increases).

Question 18

Ground proximity judgements before touchdown?

Answer 18

• The texture of the ground and the speed at which the ground passes by can be used
• The apparent size or width of the runway.

Question 19

As you get closer the runway on approach the runway becomes?

Answer 19

Wider and shorter.