1.HP_09_Vision and Illusions Page 1 OGHFA Operator’s Guide to Human Factors in Aviation Human Performance & Limitations Understanding Visual Illusions

1.HP_09_Vision and IllusionsPage 1

OGHFAOperator’s Guide to Human Factors in Aviation

Human Performance &Limitations

Understanding Visual Illusions Understanding Visual Illusions

And Disorientation And Disorientation


OGHFAOperator’s Guide to Human Factors in Aviation Human Performance

Understanding Visual Illusions and Disorientation

1. Introduction

2. Visual illusions

3. Turning illusions

4. False climb illusions

5. Preventing spatial disorientation


Disorientation and illusions - IntroductionDisorientation and illusions - Introduction

Human senses

Visual illusions

Disorientation

Turns

Pitch

How to avoid / minimise

How to recover


Human Senses - Orientation and BalanceHuman Senses - Orientation and Balance

Eyes

Inner Ear (vestibular)

Tactile (motion or position)

Rate

Rotation

Acceleration

Horizontal and Vertical

Distance and Height

Movement

Feel

Force

GravityThey work togetherThey work together

but

They are all a source of errorThey are all a source of error


Visual IllusionsVisual Illusions


Visual Illusion - False HorizonVisual Illusion - False Horizon

Rely on the flight instruments,

never on your perception;

ignore your internal instruments

1.HP_09_Vision and IllusionsPage 7Copyright Martin Aves

Visual Illusion ‘Black Hole’ Approach


Modern ‘Heavy’ EFIS / FMS equipped aircraft (VNAV)

VOR/DME, (Non-Precision Approach), Night VFR

MDA 339 ft

FAF 5 DME 3800 ft

VOR / DME

250 ft agl, 124 ft aal1.5 nm

300 ft/min

TERRAIN PULL UP

*

Visual Illusion - An Incident

1.HP_09_Vision and IllusionsPage 9 *

A long, straight-in approach A long, straight-in approach

Up sloping terrain before a runway Up sloping terrain before a runway

An airport located on the near side of a small city, An airport located on the near side of a small city,

with an irregular matrix of lights spread over with an irregular matrix of lights spread over

hillsides behind the airport.hillsides behind the airport.

Visual Illusion - ‘Black Hole’ Visual approach‘Black Hole’ Visual approach


Visual Illusions - ‘Black Hole’ Visual Approach‘Black Hole’ Visual ApproachVisual Illusions - ‘Black Hole’ Visual Approach‘Black Hole’ Visual Approach

Check altitude against range Check altitude against range

Monitor vertical speedMonitor vertical speed

Use all navigation aidsUse all navigation aids

Beware of night visual Beware of night visual

approachesapproaches


Visual Illusion - runway perspectiveVisual Illusion - runway perspective

Low High


An Incident – up sloping, long, narrow runway; down slope terrainAn Incident – up sloping, long, narrow runway; down slope terrain


An Incident – up sloping, long, narrow runway; down slope terrainAn Incident – up sloping, long, narrow runway; down slope terrain

Beware of night visual approaches

Check QNH (altimeter setting)

Always Pull Up for EGPWS warnings


Turning illusions


Turning Illusion - Leans (slow roll rate, steady turn)Turning Illusion - Leans (slow roll rate, steady turn)

Rely on the flight instruments - Rely on the flight instruments -

never on your perception never on your perception

Ignore your internal instrumentsIgnore your internal instruments


Turning Illusion Coriolis (steady turn, head movement)Turning Illusion Coriolis (steady turn, head movement)

An almost unbearable sensation that the aircraft is

rolling, pitching, and yawing all at the same time


After approx 30 seconds, the brain has no

sense of turning any more.

If the pilot perceives a turn in the opposite

direction, he may bank to re-enter the

original turn and overbank to compensate.

Turning illusion (long turn, then roll exit)

i.e.. banking during holding pattern


The aircraft makes a

sustained turn

After approx 30 seconds, the brain has no

more sense of turning

Turning illusion (long turn, then roll exit)

The pilot thinks the The pilot thinks the

aircraft is wings levelaircraft is wings level


Turning illusion (long turn, then roll exit)Turning illusion (long turn, then roll exit)

The pilot thinks the The pilot thinks the

aircraft is turning in the aircraft is turning in the

opposite direction.opposite direction.

If the aircraft is now straightened, the brain

senses a turn in the opposite direction.


Turning illusions - DefensesTurning illusions - Defenses

If your orientation is disturbed – look at and concentrate on a nearby

fixed point on the instrument panel. Check the aircraft roll attitude.

Sustained turns can be perceived as level flight or a false turn.Sustained turns can be perceived as level flight or a false turn.





False Climb illusionFalse Climb illusion

The pilot thinks the aircraft is climbing, but the aircraft pitch

attitude is level or at a lower attitude than perceived.

Gravity (1g)

Acceleration

Vertical as sensed by gravity

False vertical cues due to acceleration; give

apparent climb


False Climb illusion (during acceleration)False Climb illusion (during acceleration)

During accelerations the pilot thinks the

aircraft is climbing, but the aircraft pitch

attitude is at a lower attitude than sensed.

AccelerationAcceleration leads to Acceleration leads to

false climb attitudefalse climb attitude

Avoid the tendency to push forward.Avoid the tendency to push forward.

Concentrate on pitch attitudeConcentrate on pitch attitude.


False Climb illusion - Takeoff and Go AroundFalse Climb illusion - Takeoff and Go Around

Accelerating from 170 to 200 knots over 10 seconds • + 0.16g longitudinal acceleration• ~ 9 degrees ‘nose up’ attitude change

Use the INSTRUMENTS, follow SOPsUse the INSTRUMENTS, follow SOPs

Do not push the nose downDo not push the nose down





False Attitude Illusion on Approach - DecelerationFalse Attitude Illusion on Approach - Deceleration

Deceleration due to lowering the flaps or use of airbrake is perceived as a

nose-down sensation

On the runway, before the nose wheel touches down, the deceleration from

spoilers may be perceived falsely as a too-low pitch attitude.

Gravity (1g)

Deceleration

Vertical as sensed by gravity

False attitude due to deceleration; gives apparent nose down pitch


Simulators Cannot Imitate All IllusionsSimulators Cannot Imitate All Illusions

Simulators can provoke some illusions:

but ‘g’ never exceeds 1g

Simulators cannot imitate the false climb illusionSimulators cannot imitate the false climb illusion

Simulators have tilt, but no acceleration.


Prevent / Recover from DisorientationPrevent / Recover from Disorientation

Believe the instruments, regardless of your sensation

Don't trust your senses, particularly in low-visibility conditions

In moments of stress, base decisions on the instruments; don’t use your

‘instinct’ or feelings

Human senses can be confused and Human senses can be confused and

degrade without warningdegrade without warning

Aircraft sensors and displays are more reliable than humansAircraft sensors and displays are more reliable than humans

Aircraft sensors and displays have built-in warning and alerting Aircraft sensors and displays have built-in warning and alerting

systems; humans do notsystems; humans do not


Preventing Spatial DisorientationPreventing Spatial Disorientation

Confidence and currency in your instrument flying Use an instrument scan - practice

Prioritize workloadGolden Rule #1: First fly the aircraft

Experience Practice go-arounds

Always cross-check instruments when visual, and especially with autopilot engaged


Scan your flight instrumentsScan your flight instruments

Scan all

instruments and

believe them

Do not make control

inputs based on your

‘feelings’.

Your mental attitude

controls your

‘attitude’.

Disorientation and Illusion

Believe your flight Believe your flight

instrumentsinstruments

Believe your flight

instruments

Documents

1.HP_09_Vision and Illusions Page 1 OGHFA Operator’s Guide to Human Factors in Aviation Human Performance & Limitations Understanding Visual Illusions