text: Helicopter Landing Zones
  SECTION VI. ENVIRONMENTAL CONSIDERATIONS
  The pathfinder unit can expect to support the aviation commander and ground unit commander in many
  climates and types of terrain. The requirements for establishing a landing site or zone are similar. For aircraft to
  land safely and quickly in challenging environments, pathfinders must choose and prepare LZs carefully.
  PILOT INPUT
  4-76. The pilot considers his experiences and his responsibilities to the crew and aircraft before
  determining whether a proposed landing site is safe.
  4-77. Challenging climatic and terrain environments include extreme hot and cold weather and jungle,
  desert, and mountainous terrain. (For more detailed information on the climate, terrain, and operational
  aspects of these areas, see FM 90-3, FM 90-5, and FM 3-97.6.)
  4-78. Each area requires the pilot to know and follow special procedures. The pathfinder who also knows
  these procedures can better advise and assist aviators and the supported ground unit.
  COLD WEATHER
  4-79. Many parts of the world experience cold weather. Extreme cold and blowing snow pose special
  problems in ground operations and flight. Pathfinder mission planning includes considering the problems
  presented by ice, snow, or rain. The pathfinder's knowledge of flight procedures helps him advise the pilot
  about the existing surface conditions.
  COMMUNICATIONS
  4-80. Most locations allow generally-good radio communications. However, atmospheric electricity,
  such as the aurora borealis, can disrupt them. These events could disturb or block some frequencies.
  Mountainous terrain also restricts communications. Pathfinders might need to set up relay stations. "Radio
  skipping" happens often in cold weather areas. Radio operators often hear long-distance radio traffic on
  tactical FM networks.
  NAVIGATION
  4-81. In snow-covered areas with flat terrain, pilots might need marked and manned RPs. When aircraft
  fly over loose snow, the air movement lifts the snow and circulates it into a snow cloud. This often
  produces a zero-visibility condition known as "whiteout," through which the pilot must take off or land
  blind (Figure 4-21). Whiteout conditions place extra demands on the landing site party.
  SURFACE CONDITIONS
  4-82. The pathfinder evaluates the surface of the ground to see whether aircraft can land without sinking
  too deep into the snow. He can use a tactical vehicle to test the hardness of the surface. The landing site
  party might also try to determine the degree of ground slope, and whether obstacles lie under the cover of
  snow at each landing point.
  Distance Between Aircraft
  4-83. Pathfinders might need to increase the distance between aircraft to 100 meters and the size of the
  landing point to 100 meters in diameter.
  Landing Point Markings
  4-84. Marking the landing points presents other problems. A pilot's depth perception is impaired in
  snow-covered areas. A signalman on the ground provides a useful reference for estimating height. In
  daytime, pathfinders mark touchdown points so the pilot can find a clear and safe landing area.