Surface vs Flight Visibility

AVIATION WEATHER

CHAPTER FIVE

RVR is the horizontal distance, expressed in hundreds of feet or meters, a pilot will see by

looking down the runway from the approach end. For takeoff and landing under IFR, prevailing

visibility is not as important as the visibility within the runway environment.

Surface vs Flight Visibility

RVR and prevailing visibility are horizontal visibilities near the Earth's surface. They may be

quite different from the vertical visibility when looking down at the ground from an aircraft in

flight. For example, surface visibility may be seriously reduced by fog or blowing snow, yet only

a slight reduction in visibility is apparent when viewed from above the field. In Figure 5-15, the

airfield may be seen relatively clearly from above the fog. When descending to the level of the

fog, however, the airfield may disappear from sight. In another situation, flying into the setting

sun on a hazy day may reduce flight visibility to values less than the surface visibility. When

given the surface visibility, learn to anticipate what your flight visibility is likely to be. It may

vary, depending on other weather conditions present.

Slant R

ange V

ibility

Prevailing Visibility

1/2 Mile Due to Fog

Airfield

Figure 5-15 Surface vs Flight Visibility

Obscuring Phenomena

Obscuring phenomena are any collection of particles reducing horizontal visibility to less than

six miles. They may be either surface based or aloft. Examples include fog, haze, smoke,

volcanic ash, and blowing spray, to name a few.

Haze produces a bluish color when viewed against the ground. Although haze may occur at any

level in the troposphere, it is more common in the lower few thousand feet. Haze is associated

Weather Hazards of Turbulence, Icing, Ceilings, Visibility, and Ash Clouds

5-21