What are the characteristics of land-based chocks?

Land-based chocks are designed to secure aircraft in place and prevent movement when they are parked on the ground. The characteristic of "two polyurethane blocks joined by a line" is significant for a few reasons.

Firstly, the use of two blocks provides stability and ensures that the aircraft is captured securely, even in varying conditions. The connection by a line allows for ease of deployment and use, which is crucial in busy airfield environments where quick securing of aircraft is often necessary. Polyurethane is commonly chosen for chocks due to its durability and resistance to wear and environmental factors, making it suitable for various weather conditions and ground surfaces.

This construction provides an immediate and effective means of securing aircraft, particularly when dealing with larger or heavier models that require additional support. Other materials or single block designs might not offer the same level of protection or effectiveness in preventing movement, especially on inclined surfaces or during windy conditions.

Overall, option B highlights a practical and efficient design that meets the operational needs of securing land-based aircraft effectively.