text: Chapter 4
  y Insertion or extraction mission.
  y Weight.
  OBSTACLES
  4-23. These include any obstruction that might interfere with aircraft operation on the ground. Landing
  zones should have no tall trees, power lines, or similar obstructions on the landing site. Pathfinders must
  remove or reduce any obstacles within the landing site. This includes any rocks, stumps, holes, and thick
  grass or brush that might hinder safe landing over 0.45 meters (18 inches). Obstacles that cannot be
  removed or reduced must be marked (preferably in red) and an advisory given to the pilots. Marking will
  be done as follows:
  y If the obstacle is on the approach route, both the near and far sides of the obstacle will
  be marked.
  y If the obstacle is on the departure route, only the near side of the obstacle will be marked.
  y If the obstacle protrudes into the LZ, but not on the flight route, the near side of the obstacle
  will be marked.
  y Large obstacles on the flight route and on the LZ will be marked on all sides of the obstacle. At
  a minimum, one light is required on each of the four sides.
  ALTERNATE SITES
  4-24. Enemy action, unfavorable terrain, or changes in the tactical or logistical situation can require
  alternate landing sites. The ground unit commander usually selects these to support the tactical plan. He (or
  his representative) decides when to use them based on the recommendations of the aviation unit
  commander and the pathfinder on the site. The commander uses the fastest means to get instructions for
  using alternate sites to the pathfinders. Neither pathfinder nor aviation unit commanders can shift to an
  alternate LZ(s) unless the supported ground unit commander has delegated that authority to them.
  SECTION II. ORGANIZATION AND DUTIES
  The commander task organizes the pathfinder element to set up and operate the installations required by the
  supported unit's tactical plan. They might set these up within a single LZ or separate them widely throughout a
  large AO. The pathfinder leader normally stays at the most important site. To set up and operate one helicopter
  LZ, the commander task organizes the pathfinder element into two working parties: a reconnaissance party and
  a marking party. Each site requires its own landing site party. The control center party and the release point
  party provide the same function for LZs or DZs.
  CONTROL CENTER
  4-25. The control center (CC) coordinates aircraft in and around an LZ or DZ and promotes a safe,
  orderly, and speedy flow of air traffic. Upon arrival in the area, the pathfinder leader selects the exact
  location of the CC. He positions it to allow visual control of aircraft in and around the LZ or DZ.
  4-26. For helicopter LZs, the most desirable CC location is along the aircraft flight route, but displaced
  from the landing site. This helps prevent enemy EW assets from compromising the actual landing site
  location, even if the tactical situation dictates that the pathfinder leader remain on the site for control
  purposes. For an LZ with more than one landing site, or for any LZ during reduced visibility, the
  pathfinder leader locates the CC where it can act as a manned RP or final approach fix to provide positive
  navigational assistance to arriving aircraft.
  4-27. The RP is an established traffic control checkpoint. It is the final navigational checkpoint for
  aircraft approaching the landing site or approaching air-delivery facilities in an LZ or DZ.
  4-28. During the air movement phase of an air assault operation, helicopter serials also use the RP as a
  final coordination point for control of planned ground or aerial supporting fires in and around LZs. The air