1. Rotary Wing Night Flight Part II7 1 7

2. Reference FM 2

3. Contents
Terrain Interpretation 3

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. QUESTIONS?