Because they are attached to the fuselage, or "skin," of the aircraft, belly hooks are regulated by the various worldwide aviation regulatory agencies.
For small to mid-size utility helicopters performing external load work, belly hooks are typically mounted to the fuselage using either a sling or a suspension configuration.
Because they are not attached directly to the airframe, they do not require aircraft-specific certification and can be used on a wide variety of helicopter models.
Key components of a cargo hook include the load beam, the keeper, and the attach point.
Rotorwash can also pose a hazard, causing difficulty to nearby personnel walking or standing, as well as blowing unsecured items around.
[13] 3 days of the US Army Air Assault course is dedicated to training and testing servicemembers on the inspection of sling loads and procedures for hook-up operations.