What is the PRIMARY concern when working with high boom angles?

When working with high boom angles, the primary concern is backward stability. As the boom angle increases, the center of gravity of the load and the crane shifts, which can lead to a decreased stability margin. High boom angles can reduce the effective reach of the crane and may cause the load to swing backward, increasing the risk of tipping if the crane is not properly stabilized.

Backward stability is crucial because it involves ensuring that the crane remains stable against the potential of overturning towards the rear. This is especially important as it relates to the load’s weight distribution and how it interacts with the crane's base. Proper rigging techniques and an understanding of the crane's load chart become vital in maintaining backward stability when operating at high boom angles.

While concerns such as forward stability, side stability, and cross wind stability are important in their own right, they do not address the specific challenges presented by high boom angles as directly as backward stability does. The dynamics involved when lifting at these angles make it essential to focus on ensuring that the crane does not tip backwards, which could lead to accidents and serious safety hazards.