Hazards Associated WithHazards Associated WithFlying at NightFlying at Night

Presented byPresented by

NameNameTransport Canada, System SafetyTransport Canada, System Safety

Transport Canada

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Main Causes of Night AccidentsMain Causes of Night Accidents

• VFR-into-IMC

• CFIT

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CARsCARs• CAR 602.115 three mile visibility for

night VFR

• CAR 703.27 prohibits en route night VFR at less than 1000 ft above the highest obstacle along specific routes

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The EyeThe Eye

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Factors that Affect ourFactors that Affect ourNight VisionNight Vision

• Night vision

• Two blind spots

• Lack of colour vision

• Reduced acuity

• Reduced depth perception

• Night myopia

• Visual hypoxia

• Night blindness

• Effects of aging

• Carbon monoxide, alcohol, drugs, fatigue, smoking

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Night VisionNight Vision• Process requires about 30 min• Rods become adjusted to darkness • Off-centre viewing important during night flights• Smoking, carbon monoxide, hypoxia, certain

drugs adversly affect night vision• Avoid bright lights to preserve night vision• Red light preserves night vision but severley

distorts colours

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Two Blind SpotsTwo Blind Spots• Physiological blind spot

• Central blind Spot

• Use an off-centre scanning technique

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Lack of Colour VisionLack of Colour Vision

• Rod vision is unable to discriminate colours

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Reduced AcuityReduced Acuity• Central vision blindness at night

• High rod-to-optic nerve fiber ratio reduces acuity

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Reduced Depth PerceptionReduced Depth Perception

• Rod vision and pupil dilation reduces depth perception

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Night MyopiaNight Myopia• Shortsightedness occurs during dark focus

• Periodically change focus distance

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Visual HypoxiaVisual Hypoxia

• The retina of the eye is more sensitive to hypoxia than any part of our body

• One of the first symptoms of hypoxia is a decrease in night vision

• Effects most noticeable starting at 5000’ above ground level to which you are acclimated

• Smokers are much more susceptible to hypoxia due to the build-up of carbon monoxide in their blood

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Night BlindnessNight Blindness

• Functionally blind due to pigment deficiency in rods

• Night blindness induced within 60 days on diet lacking vitamin A

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Effects of AgingEffects of Aging• Pupil size decreases• Range of eye focus is

reduced• Visual acuity is

reduced• Colour discrimination

becomes more difficult

• It takes longer to process visual information in general

• Sensitivity to glare increases

• Takes longer to read under dim light conditions

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Night Illusions & LimitationsNight Illusions & LimitationsIllusions

Autokinesis (objects appear to shift)False reference (stars or lights near horizon)Venus and sirius (false aircraft)Night myopia (dilation, inability to focus)Somatogravic (acceleration with pitch)

LimitationsNight blind spot (rods & cones, stars, etc)Light to dark adaptation (2 hours)

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Focused Scan Problems: NightFocused Scan Problems: Night• Night blind spot (A.I.P. AIR 3.7)

– centre portion of eye is blind at night

• Night Scan– look 10-150 away from what you try to see– night vision is affected by altitude– drugs, alcohol, smoking and fatigue adversely

affect night and day vision

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Pre-Flight Planning

• Route Study

• Weather Conditions

• Equipment

• Alternate Plan

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Ground OperationsGround Operations

• Taxi speed illusion

• Geographic disorientation

• Risk of collision

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Take off and ClimbTake off and Climb

• Lining up

• Take off into the black-hole

• Somatogravic illusion

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CruiseCruise

• Ability to detect and monitor weather

• Terrain detection

• Geographic disoriention

VMC into IMC Conditions

178 Seconds

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Approach and LandingApproach and Landing

• Runway detection

• Black-hole approach

• Effects of runway slope

• Runway dimensions

• Atmospheric conditions

• Runway lighting

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Black-hole DiagramDiagram

3 degree glidescope

Arc of Constant Visual Angle

Arc Radius

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Be alert for the black-hole illusion Be alert for the black-hole illusion if you observe these conditionsif you observe these conditions• An airport that is on the near side of a

brightly lit city with few or no terrain features or lights between you and the airport

• An airport that is on the coast or lake shore

• An airport in a very sparsely settled areas

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Fatigue Induces Human ErrorFatigue Induces Human Error

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Preventative MeasuresPreventative Measures• Recognize normal human visual limitations

involved know what they are and circumstances they are most likely to occur

• Learn which airports are conducive to visual illusions at night and use the Canada Flight Supplement (CFS) for more information and restrictions during hours of darkness

• Use flight instruments for approaches especially those that provide glide path information (i.e., ILS, DME readouts and altimeter)

• Use airport aids to vision (i.e., VASIS, T-VASIS)

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More Preventative MeasuresMore Preventative Measures• Avoid visual long straight-in approaches (overfly

airport if necessary)• For geographic disorientation use radio navigation

and GPS if fitted• Pay attention to alert devices (radio, altimeter,

GPWS)• Double check your own expectations and

perceptions• Ensure adequate sleep and nutrition