text: External Loads
  SLING LENGTH
  5-63. Lengthening the slings that attach the load to the aircraft reduces the load's stability in flight. The
  shorter, the better, as long as the sling measures at least 6 feet long. Also, the more vertical the attached
  sling, the less stress on those that are more horizontal. Figure 5-16, page 5-22, shows how sling angle
  affects load stress.
  Figure 5-16. Load chart of sling tension at various angles of inclination with a load
  of 1,000 pounds.
  EFFECT OF VERTICAL SLING
  5-64. A vertical sling carrying 3,000 pounds has 3,000 pounds of stress on it. That means the stress
  equals the weight of the load.
  EFFECT OF 45-DEGREE SLING
  5-65. A 45-degree sling carrying 3,000 pounds has 4,242 pounds of stress on it. That means the stress
  equals nearly one-and-a-half times the weight of the load.
  EFFECT OF 5-DEGREE SLING
  5-66. A 5-degree (almost horizontal) sling carrying 3,000 pounds has 34,419 pounds of stress on it.
  That means the stress equals more than ten times the weight of the load.
  HOOKUP AND RELEASE PROCEDURES
  5-67. Hooking up a load requires a team effort. The signalman must position the aircraft over the load.
  He does this so the slingload team can discharge the static electricity and attach the load to the aircraft as
  quickly and safely as possible. Most of the time, the air crew releases the load. This seldom requires any
  ground crew except the signalman.