What is the most common simple pulley system used for rescue?

The most common simple pulley system used for rescue is the 3:1 system, also known as the Z Rig. This setup is widely utilized because it strikes a balance between mechanical advantage and ease of use. In a 3:1 system, one rope is threaded through multiple pulleys, allowing rescuers to pull three times the amount of weight they are moving with a single pull. This makes the system highly effective for lifting heavy loads, which is often necessary in rescue operations.

The design of the Z Rig allows for both efficiency in pulling strength and control during rescue scenarios, which is critical when managing life-saving operations. Additionally, this system can be set up relatively quickly and doesn't require complex rigging skills, making it accessible for rescuers under pressure.

In contrast, the 2:1 system offers less mechanical advantage, which may not be sufficient for many rescue situations involving heavier loads. The 4:1 system provides a greater mechanical advantage but can be more cumbersome and slower to deploy, while the compound pulley system, while powerful, introduces additional complexities that may not be needed for straightforward rescue tasks.