text: Helicopter Landing Zones
  SECURITY
  4-100. Success of the ground unit commander's mission relies on site security. Because jungle terrain
  provides cover and concealment, landing site security presents a constant challenge. The pathfinder team
  leader coordinates with the flight commander to set a specific time to light the site.
  LIFTOFFS AND LANDINGS
  4-101. The pathfinder orients the site to the direction of the wind. He keeps departure obstacle ratios low
  due to climatic conditions, jungle vegetation, and helicopter's reduced lift capability. Because ground
  effects reduce the aircraft's lift efficiency, the pilot hovers as low as possible and lingers no longer than
  necessary.
  DESERT
  4-102. The typical desert is a dry, barren region, generally treeless and sandy. It has environmental
  extremes, with violent and unpredictable weather changes. Its terrain conforms to no particular model.
  Frequent clear days offer unequaled visibility and flight conditions, but a sudden sandstorm immediately
  halts all operations. Successful desert operations require special training, acclimatization, and great
  self-discipline.
  COMMUNICATIONS
  4-103. In desert operations, the radio offers the best way to communicate. The low, rolling terrain allows
  good radio range. Due to the increased distances involved in military desert operations, FM radio
  communications might prove inadequate, especially in the higher FM frequencies. Pathfinders, aircraft, and
  ground crew must all have high-frequency radio equipment. Sand or dust in equipment or a poor electrical
  ground cause most communication problems. Due to the increased distances between land force units
  engaged in desert operations, helicopters might provide air or ground relay or help deploy ground radio
  rebroadcast facilities.
  NAVIGATION
  4-104. Many of the conditions experienced in cold weather operations resemble those in desert operations.
  Pathfinders and pilots find distances and altitudes hard to judge in the desert. The lack of definable terrain
  features makes navigation difficult, especially at night and over long distances. Also, the sameness of the
  terrain can influence a pilot to pay less attention to his surroundings. Pathfinders might have to mark and
  man release points.
  LANDING SITES
  4-105. The climatic conditions in the desert profoundly affect the setup and operation of landing sites.
  Most importantly, the pathfinder must consider density altitude, wind, and sand (dust). Sand on a landing
  site can produce brownout conditions similar to those in snowy areas, so the same precautions apply. This
  makes a rocky area a better landing site than a sandy hollow, depression, or valley.
  WIND
  4-106. Desert winds generally calm down for an hour or two around sundown. Another calm occurs
  before sunrise. Other than those times, desert winds can drive dense clouds of dust and sand with hurricane
  force. Strong winds naturally raise dense clouds of dust and sand, and rapid temperature changes often
  follow strong winds. The pathfinder leader must consider what times of day the wind will allow him to
  operate the landing site.
  4-107. The extreme heat often experienced in the desert also affects the aircraft's ACL. When supporting a
  ground unit, the pathfinder leader coordinates with the aviation element to determine the ACL for each
  type of aircraft. Both the minimum distance between aircraft and the size of the landing point might