text: Helicopter Landing Zones
  Night Operations
  4-19. During night operations, as the pilot gets closer to the landing point, he needs a wider area for a
  safe approach than just the 16-degree sector. Therefore, the minimum width of the approach and exit path,
  illustrated by the darker shaded area, must be equal to or wider than the width of the landing point that
  must be cleared to a maximum height of 2 feet (Figure 4-1). The length of the minimum width area,
  dimension X, will vary depending on the size of the landing point (Table 4-2). Follow along as we use a
  UH-60 Blackhawk as an example to help clarify the night approach and exit path criteria. Table 4-1
  identified the UH-60 Blackhawk as a size 3 helicopter. Next, you must determine the landing point area
  that must be free from obstructions and grass cut to maximum height of 2 feet. Figure 4-2 shows 50 meters
  as the area needed for a size 3 landing point. Therefore, the minimum width of the night approach and exit
  path is 50 m. The minimum width distance intersects the 16-degree V-shaped arc (night approach and exit
  path) 180 meters from the center of the landing point. In other words, the night maximum obstruction angle
  applies to the complete approach and exit path; both the rectangular-shaped wedge (dark shaded area of the
  diagram) as well as the 16-degree "V"-shaped arc (light shaded area and dotted line).
  Table 4-2. Length of minimum width area.
  Note: The aviation unit commander makes the final decision on minimum landing requirements.
  He bases his decision on the effects of air density, slope, and surface conditions. He explains
  these requirements verbally during early mission planning.
  Along the Long Axis
  4-20. Allows the pilot a better opportunity to identify the TDP and obstacles, select the best flight path,
  and prevent overflying the TDP. It also allows the pathfinder to maximize the space available in the site.
  DENSITY ALTITUDE
  4-21. Altitude, temperature, and humidity determine the density altitude. As each of these conditions
  increase, aircraft lift capabilities decrease. Planners should try to remember that as the density altitude
  increases, the size of the LZ also increases. This will also be a consideration for the aviation unit
  commander when determining the authority for Pathfinders to reduce TDP size or obstacle ratio.
  LOADS
  4-22. When fully loaded, most helicopters can neither climb nor descend vertically. They need a larger
  area and better approach or departure routes than when they carry lighter loads. Other load
  considerations are—
  y Equipment or personnel.
  y Internal or external load.