Rotary Wing Night Flight Part II 7 1 7

Reference FM 3-04.203 2

Contents Terrain Interpretation 3

Terrain Interpretation Visual Recognition Cues Object Size- The larger the object, the easier it is to recognize at night Object Shape- Some objects are recognizable by their shape/silhouette. Natural and man-made objects can be identified using their shape and outline as viewed from different angles. Contrast- The contrast between an object and its background can aid in identification. Color, Texture, Background-These objects determine an objects reflective quality. 4

Terrain Interpretation Factors Affecting an Aircrew Members Ability to Use Cues Ambient Light- Reduced Levels at night decrease visual acuity Terrain interpretation by size, shape, and contrast becomes more difficult at lower light levels Viewing Distance- Viewing angle becomes smaller as distance from object increases. Range is difficult to estimate at night and can lead to miscalculation of object size Distance at which objects can be viewed depends on ambient light level 5

Terrain Interpretation Factors Affecting an Aircrew Members Ability to Use Cues Flight Altitude High Altitude- Changes in viewing angle and distance will change the apparent shape of object. As flight level increases, contrast begins to fade and objects will blend (Low Altitude)- Terrain is more clearly defined and contrast greater at lower altitudes Man-made objects and natural features more easily recognized Viewing area is reduced requiring lower airspeeds. 6

Terrain Interpretation Factors Affecting an Aircrew Members Ability to Use Cues Moon Angle Higher moon angles produce greater levels of illumination and reduce shadows. Lower moon angles create shadows that make terrain interpretation difficult Azimuth angle affects how objects appear and how much contrast is observed. 7

Terrain Interpretation Factors Affecting an Aircrew Members Ability to Use Cues Visibility Restriction Adverse weather will restrict visibility and reduce ambient light levels causing loss of visual acuity. Conditions usually degrade gradually, making them difficult to detect Weather conditions can make certain maneuvers difficult and complicated, as well as leading to visual illusions due to swirling dust, snow, sand, or rain. 8

Terrain Interpretation Factors Affecting an Aircrew Members Ability to Use Cues Terrain- The nature of terrain determines the amount of light reflected from the surface of the earth Deserts- Texture and color provide optimum reflection of ambient light. Blowing dust/sand makes flying difficult Lack of terrain and vegetation can make navigation and concealment quite difficult Vegetated Rolling Terrain- Rivers and terrain provide distinct changes in elevation. Dirt roads and farm structures provide most distinguishable manmade features. 9

Terrain Interpretation Factors Affecting an Aircrew Members Ability to Use Cues Terrain (cont) Mountains Large, distinct terrain features and silhouetting enhance interpretation. Barren mountains reflect light well Jungle Similar to heavily vegetated rolling terrain. Vegetation may mask changes in elevation making navigation difficult 10

Terrain Interpretation Factors Affecting an Aircrews Member Ability to Use Cues Terrain (cont) Arctic Similar to desert in reflectivity characteristics Snow can cause glare Blowing snow creates a hazard to flight Rotor wash can create a path visible for hours due to blowing snow, even during periods of heavy snowfall 11

Terrain Interpretation Factors Affecting an Aircrews Member Ability to Use Cues Seasons- Seasons of the year affect ambient light. Aviation focuses on two seasons, winter and summer. Winter- Contrast improves as areas lack vegetation Ground snow may increase reflectivity Barren trees may be harder to see Cloud cover and reduced visibility are prevalent in winter Heavy buildups of snow may mask terrain 12

Terrain Interpretation Factors Affecting an Aircrew Members Ability to Use Cues Seasons (cont) Summer- Increased vegetation masks terrain and man-made objects Concealment and camouflage are much easier due to increased vegetation 13

Terrain Interpretation Other Considerations to Terrain Interpretation- Terrain Features- Analysis of the terrain is most reliable means of orientation. Features easily identified are those unique in shape and/or distinct change in elevation. Silhouetting- Sighting a darkened shape of an object against a lighter background. Useful for locating both terrain and man-made objects 14

Terrain Interpretation Other Considerations for Terrain Interpretation (cont) Cultural Features Roads- Provide excellent contrast. Amount of light reflected will depend on road surface. Intersections-When accurately plotted make good checkpoints or orientation cue Bridges- Good checkpoint if they have vertical development 15

Terrain Interpretation Other Considerations for Terrain Interpretation (cont) Cultural Features (cont)- Railroads- Aircrew members can easily identify them, but vegetation can often mask them from view. Buildings- Isolated, large, or light-colored buildings provide excellent contrast. Cemeteries- Most cemeteries have light-colored, polished headstones contrasting well against a natural background. 16

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