text: Chapter 5
  External Loads
  Carrying cargo and equipment outside the helicopter eliminates many of the
  problems that other modes of transportation have. Helicopters move cargo by
  external slingload when—
  y The cargo compartment cannot hold the load.
  y The load exceeds the helicopter's internal load limitation.
  y The ground crew must load or unload the cargo at once.
  y Landing zone conditions prevent the aircraft from touching down.
  Pathfinder-qualified Soldiers prepare to organize and control external load pickup or
  drop-off sites as an integral part of LZ operations. The supported unit provides a
  detailed load plan, to include rough weights and sequences of load movement. This
  ensures the correct and rapid movement and placement of cargo.
  LANDING POINTS
  5-1. Conditions such as a dusty surfaces, darkness, or obstacles often require pathfinders to increase
  the minimum spacing between loads and landing points. This reduces the number of helicopters that can
  safely operate at the site at the same time, the size of the mission that can be supported, and the overall
  speed of the operation.
  TYPES OF LOADS
  5-2. All external loads fall under one of three types: high density, low density, or aerodynamic. Each
  exhibits unique characteristics in flight. Pathfinders determine the type, size, and weight of the load during
  the planning phase of the operation.
  HIGH DENSITY
  5-3. The high-density load offers the best stability.
  LOW DENSITY
  5-4. The low-density load offers the least stability.
  AERODYNAMIC
  5-5. The aerodynamic load lacks stability until the airstream stabilizes the load. The ACL depends on
  the type of aircraft, the age of the airframe, the altitude above sea level, the temperature, the humidity, and
  the aviation unit's SOP.