What caused the damage described as side loading with the hoist line jumping off the sheave?

• A. The boom was side loaded and the hoist line jumped off the sheave
• B. The load was too heavy for the crane
• C. The jib angle was too steep
• D. The outriggers were not deployed

Answer: (A)

Side loading the boom creates sideways forces in the hoisting system. When the boom is pushed to one side, the hoist line no longer travels cleanly around the upper sheave; it is driven toward the edge of the groove and can ride out or slip off the sheave under tension. That lateral misalignment is what allows the line to jump off the sheave, leading to damage. Other scenarios—like an overload, a steeper jib angle, or not deploying outriggers—would produce different issues (overload conditions, altered geometry, or instability) but not the specific mechanism of the hoist line losing its seat in the sheave.