A lattice boom mobile crane is set up on outriggers with 100% extension on uneven ground, resulting in one outrigger pad losing full contact. Considering CSA Z150 safety requirements, what specific force condition is primarily impacted, potentially leading to instability and a tip-over?

Question: A lattice boom mobile crane is set up on outriggers with 100% extension on uneven ground, resulting in one outrigger pad losing full contact. Considering CSA Z150 safety requirements, what specific force condition is primarily impacted, potentially leading to instability and a tip-over?

Answer options:

• Nominal rated capacity is reduced by 25%. ✅ The crane's effective centre of gravity shifts significantly, reducing stability in the direction of the dangling outrigger.
• Hydraulic pressure in the other outriggers increases proportionally, causing relief valve activation.
• The crane instantly becomes a rubber-tired crane, and the load chart for 'on tires' applies.

Correct answer: The crane's effective centre of gravity shifts significantly, reducing stability in the direction of the dangling outrigger.

Explanation: Losing full pad contact on an outrigger significantly compromises the crane's stability polygon. This effectively shifts the centre of gravity of the crane and load outside the reduced support base, creating an overturning moment that can lead to a tip-over, even if within chart capacity on paper.