The aerial apparatus is least stable when the aerial device is operated __________- to the longitudinal axis of the truck.

• A. Perpendicular
• B. Parallel
• C. At an angle
• D. Diagonally

Answer: (A)

Stability hinges on where the weight of the aerial and its load acts relative to the truck’s support base. The outriggers form a footprint, and the further the overall center of gravity shifts away from that footprint, the larger the tipping moment.

When the aerial device is directed straight out to the side of the truck (perpendicular to the truck’s length), the load’s line of action moves farthest from the center of the outriggers. This creates the greatest tipping moment and makes the system least able to resist overturning. If the lift runs parallel to the truck’s length, or at an angle, the weight remains more within the base footprint or the tipping moment is reduced, so stability improves.