What type of load is caused by wind impact on an aerial device?

The correct answer is dynamic load, as wind impact on an aerial device introduces forces that vary in magnitude and direction with time. Dynamic loads are characterized by their ability to change and fluctuate, which is precisely what happens when wind interacts with the structure of the aerial device. This interaction creates stresses that the aerial ladder or platform must accommodate, as the wind can cause oscillations and movement.

When considering static loads, these are constant forces acting on a structure, such as the weight of the aerial ladder itself or any equipment placed upon it, which do not change over time. A combined static and dynamic load would imply that both types of loads are acting together, but wind impact is typically categorized solely as a dynamic load due to its inherently variable nature. Variable loads suggest a broader scope of changing forces that might not specifically pertain solely to wind, hence, would not be the most accurate classification for the specific effects of wind on aerial devices.