What is the effect of luffing the boom on load capacity and stability?

• A. It reduces horizontal reach and may change CG, often reducing capacity
• B. It increases horizontal reach and increases capacity
• C. It has no effect on capacity and only changes the steering characteristics
• D. It improves stability when the boom is raised

Answer: (C)

Luffing the boom changes the geometry of the lifting arrangement: you tilt the boom in the vertical plane, which moves the load closer to or farther from the crane’s base and raises the load higher. This shifts the lever arm and the overturning moment the ballast and outriggers must resist, so the load capacity is not fixed—it depends on the boom angle, radius, and the crane’s configuration as shown on the load chart. Stability is affected because changing the boom angle alters the crane’s center of gravity and how the weight is distributed relative to the foundation. In many cases, raising the boom (luffing) reduces horizontal reach and can reduce capacity for a given load and radius, and it does not reliably improve stability. The exact impact should always be checked on the crane’s load chart for the specific configuration.