Hazards to Flying at Night
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Transport Canada Transports Canada Hazards Associated With Flying at Night Presented by Name Transport Canada, System Safety Transport Canada Transports Canada Main Causes of Night Accidents • VFR-into-IMC • CFIT Transport Canada Transports Canada CARs • 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 Transport Canada Transports Canada The Eye Transport Canada Transports Canada Factors that Affect our Night 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 Transport Canada Transports Canada Night 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 Transport Canada Transports Canada Two Blind Spots • Physiological blind spot • Central blind Spot • Use an off-centre scanning technique Transport Canada Transports Canada Lack of Colour Vision • Rod vision is unable to discriminate colours Transport Canada Transports Canada Reduced Acuity • Central vision blindness at night • High rod-to-optic nerve fiber ratio reduces acuity Transport Canada Transports Canada Reduced Depth Perception • Rod vision and pupil dilation reduces depth perception Transport Canada Transports Canada Night Myopia • Shortsightedness occurs during dark focus • Periodically change focus distance Transport Canada Transports Canada Visual 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 Transport Canada Transports Canada Night Blindness • Functionally blind due to pigment deficiency in rods • Night blindness induced within 60 days on diet lacking vitamin A Transport Canada Transports Canada Effects 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 Transport Canada Transports Canada Night Illusions & Limitations Illusions 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) Limitations Night blind spot (rods & cones, stars, etc) Light to dark adaptation (2 hours) Transport Canada Transports Canada Focused 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 Transport Canada Transports Canada Pre-Flight Planning • • • • Route Study Weather Conditions Equipment Alternate Plan Transport Canada Transports Canada Ground Operations • Taxi speed illusion • Geographic disorientation • Risk of collision Transport Canada Transports Canada Take off and Climb • Lining up • Take off into the black-hole • Somatogravic illusion Transport Canada Transports Canada Cruise • Ability to detect and monitor weather • Terrain detection • Geographic disoriention VMC into IMC Conditions 178 Seconds Transport Canada Transports Canada Approach and Landing • • • • • • Runway detection Black-hole approach Effects of runway slope Runway dimensions Atmospheric conditions Runway lighting Transport Canada Transports Canada Black-hole Diagram Arc Radius 3 degree glidescope Arc of Constant Visual Angle Transport Canada Transports Canada Be alert for the black-hole illusion if 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 Transport Canada Transports Canada Fatigue Induces Human Error Transport Canada Transports Canada Preventative 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) Transport Canada Transports Canada More 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
