Night Vision - HawkPilot.com

Rotary Wing Night Flight

Part I

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Reference FM 3-04.203

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Contents

I. Night Vision

II. Hemispherical Illumination and Meteorological Conditions

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I. Night VisionA. Combat Visual Impairments 1. Night Laser Hazard•

Eye is more vulnerable at night, iris of eye opens more to accommodate lower levels of illumination

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Laser damage to eyes includes flash blindness, retinal burns, impaired night vision

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Normal cockpit tasks, obstacle avoidance, use of acquisition/targeting systems become difficult or impossible

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I. Night Vision A. Combat Visual Impairments 2. Nerve Agents•

Exposure of the eyes to nerve agents adversely affects night vision

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Contact with nerve agents result in miosis (constriction of the pupils)

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Repeated exposure is cumulative

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Severe miosis can last for approximately 48 hours and full recovery may take up to 20 days.

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I. Night Vision B. Aircraft Design Limitations and Solutions 1. Design Eye Point (DEP)•

Point where crew station designer specifies where aircrew member’s eyes should be

•

Allows aircrew member to acquire information easily and quickly

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Proper seat position required to achieve DEP. Aircrew member should be able to see ground approximately 12 feet in front of nose of aircraft.

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I. Night Vision B. Aircraft Design Limitations and Solutions 2. Aircrew Coordination•

Safest and most effective solution to overcoming design limitations.

•

Requires interaction, communication, and actions between all crewmembers.

3. Additional crewmembers•

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Assist aircrew members by providing information on hazards, obstacles, and unintentional drift or movement.

I. Night Vision B. Aircraft Design Limitations and Solutions 4. Lighting•

Minimizing lighting without hindering reading of essential instruments allows maximum visibility outside the aircraft

•

Balance tactical needs with need to comply with Federal Aviation Regulations (FARs) and local policies

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II. Hemispherical Illumination and Meteorological Conditions A. Light Sources 1. Lunar Light•

Moon Angle changes about 15 degrees per hour (1 degree/4 minutes)

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Light is brightest at highest point or zenith

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There are four distinct phases of lunar light and illumination

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II. Hemispherical Illumination and Meteorological Conditions A. Light Sources 1. Lunar Light-Phases of Lunar Light Cycle a)

New Moon-

• •

Last approximately 8 days Moonlight increases towards end of phase when approximately 50% of moon is illuminated

b)

First Quarter-

• • •

Last approximately 7 days Begins when moon is approximately 50% illuminated Ends when slightly less than 100% of moon is illuminated

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II. Hemispherical Illumination and Meteorological Conditions A. Light Sources 1. Lunar Light-Phases of Lunar Light Cycle (cont)c)

Full Moon-

• •

Begins when 100% of disk is illuminated Ends 7 days later when 50% of disk is visible

d)

Third Quarter-

• • •

Last approximately 7 days Begins when about 50% of moon is visible Ends when 2% or less is visible

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II. Hemispherical Illumination and Meteorological Conditions A. Light Sources 2. Solar Light•

Unusable when sun is 12 degrees below horizon (48 minutes after sunset) This is End Evening Nautical Twilight (EENT)

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Becomes usable when sun is 12 degrees below horizon (48 minutes before sunrise) This is Beginning Morning Nautical Twilight (BMNT)

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End Evening Civil Twilight and Beginning Morning Civil Twilight (EECT/BMCT) occur when sun is 6 degrees below horizon.

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II. Hemispherical Illumination and Meteorological Conditions A. Light Sources 3. Other Sources of Illuminationa)

Starlight•

Provide some background lighting

• b)

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Provide about 1/10th the illumination of a quarter moon Artificial Light

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Lights from cities, automobiles, fires and flares provide small amounts of illumination

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Artificial light is most pronounced during overcast conditions

II. Hemispherical Illumination and Meteorological Conditions B. Other Considerations1. Meteorological Effects • • •

Predicting light levels not always accurate Adverse Weather difficult to detect at night Decrease in visual acuity and loss of horizon can be very subtle

2. Clouds•

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Reduce hemispherical illumination depending on amount of absorption/reflection Aircrew members should monitor ambient light and cloud coverage to determine if conditions are deteriorating.

II. Hemispherical Illumination and Meteorological Conditions B. Other Considerations 3. Restrictions to Visibility•

Loss of Celestial Lights- Overcast clouds may cause moon and stars to fade and/or disappear

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Loss of Ground Lights- City or rural lights fade due to obscuration

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Reduced Ambient Light Levels- Obscurations will reduce forecast light levels

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II. Hemispherical Illumination and Meteorological Conditions B. Other Considerations3. Restrictions to Visibility (cont)•

Reduced Visual Acuity- Best-Case visual acuity is based on high ambient night illumination, high contrast, and clear visibility.

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Best resolution with aviator’s night vision imaging system (ANVIS) occurs somewhere between 25 to 50 percent moon illumination

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Light levels above 50 percent moon illumination do not improve ANVIS resolution

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Scintillation- Low ambient light levels increase video noise and is seen as a sparkling effect by crewmembers.

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II. Hemispherical Illumination and Meteorological Conditions B. Other Considerations4. Lightning•

Creates the same effect as a flare

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Intensity depends on proximity of the flash and strength of the storm

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Night vision may be temporarily impaired if the aircrew is too close to lightning activity

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QUESTIONS?

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