Explain the effect of the following factors on visual perception during an approach: 

Steep and shallow approach paths

A student pilot will have got to know how their local runway looks on a normal practice approach
They also understand how the perspective changes if they are too steep or lower than normal

If landing on a longer runway than normal the runway will appear narrower than usual
The illusion is that the aircraft is too high

Length, Width and Texture of a runway

A runway wider than usual will appear closer than it is resulting in the illusion of being too low and resulting in a flare and hold-off that is too high

A runway that is narrower than usual appears further away than it really is, this gives the illusion of being too high

The flare may be delayed resulting in earlier than expected contact with the runway

When adopting a new approach this can result in him being dangerously low
When flying into a shorter runway than normal the runway will appear wider than usual – giving the illusion that the aircraft is too low.

On adapting to this perception the approach then becomes too high 

Intensity of approach lights

Visual landing aids assist the pilot to approach the runway at the correct angle which on average is a 3 degree glide slope approach

Try to get  as much practice at different airfields without using landing aids

Explain the effect of sloping terrain on visual perception.

This can cause dangerous illusions in perspective resulting in too high or too low an attitude 

Describe the optical characteristics of the windshield.

Vision can be impaired if the windshield is dirty or scratched

When washing or wiping a windshield, this must be done vertically rather than horizontally as any scratches are less likely to be seen as a false horizon.

Mark on the windscreen can act as a focal trap, thus you may not see anything outside.

Explain the effect of fog, haze, and/or dust on visual perception.

A major reduction in sharpness / acuity

As fog haze and dust decrease the level of sunlight increases – improving visual perception  

Explain relative motion.

When an adjacent vehicle is moving the occupants in the stationary one think it is they who are moving

Explain the effect of a false horizon on visual perception.

A false horizon can mislead and result in the pilot selecting false attitudes and receiving conflicting information

Describe conditions which can lead to the creation of a false horizon.

Sloping layers of cloud by day, angled lines on the ground or areas of light at night can produce a false horizon

This can mislead and result in the pilot selecting false attitudes and receiving conflicting information

Explain the see and avoid method of avoiding mid-air collisions.

To understand the time factor in seeing / avoiding, we must first look at the time taken for each individual part

Looking – 0.1 – 0.2 secs
Seeing – 0.2 – 0.3 secs
Recognising – 0.7 – 1.0 secs
Evaluating / deciding – 2.0 – 3.0 secs
Physical action – 2.0 – 3.0 secs

Total time – 5- 7.5 secs

By the time we see a potential threat, and conduct an evasive maneuver, the time passes is around the 5 – 7.5 seconds. It is vital we maintain a good lookout to see potential threats as soon as possible. 

Explain the following visual illusions, and describe methods of managing this:

Autokinesis 

A single light source at night can appear to “dance” and move even though it is stationary
This is the autokinetic effect
More likely if only one light source
The brain has difficulty making sense of the single pinpoint of light and will move it around to try to find a pattern / make some sort of sense out of it 

Stroboscopic illumination illusion / flicker vertigo

Occurs when there is a bright light source in the visual field that is being interrupted intermittently and rapidly
Eg propellor / rotor blades
The bright flickering effect can cause dizziness and feeling unwell
Sometimes convulsions seizures can occur
If encountered pilot should alter their gaze , use a sunshade or re-position the aircraft to avoid the flicker

Break off phenomenon 

Flight is in conditions of very little visual, mental or physical stimulation with low workload
Break-off phenomenon is where the pilot feels psychologically detached from surroundings
May feel as if they are outside the cockpit looking in
Aircraft may feel as though balancing on a pinhead and about to fall off
Not serious or long lasting 

Can occur inn altitude or hazy flight conditions

Considered normal response to low visual stimulus

How to deal with this

Black hole phenomenon

Serious disorientation can occur with a pilot at night when there is no horizon and no outside visual references on the ground
Visual judgement of height above the ground is impossible as there is no depth perception
This is a black hole phenomena
Must fly on instruments only and ignore all body sensations

Empty Visual Field Blindness

Also known as Low Visual Stimulus Shortsightedness

Occurs where the visual field looks the same in all directions and is unbroken

For example in haze or over a smooth sea surface

When the eye is un stimulated it takes up it’s natural relaxed focal length which is 3-4 metres

Gives a false impression that the pilot is doing a good lookout

This can be overcome by 

-the pilot anticipating likely conditions for it to occur

-consciously stretching the focal length of the eyes eg by looking outside at the wingtip

-periodically gazing far out to a distant cloud or other feature

Explain effective visual search techniques.

When scanning the sky for other aircraft, it is vital we conduct a good lookout procedure

Divide the area ahead into 20 degree sectors and scan 

Take into account the time it takes to recognise what the eyes are seeing – at least 1.5 seconds

To account for glare and other factors make the time 2 seconds