What type of sign is used to provide mandatory instructions at an airfield?

The type of sign that provides mandatory instructions at an airfield is the mandatory instruction sign. This sign is specifically designed to convey essential rules and regulations that must be followed by aircraft, pilots, and ground personnel. These signs are typically used to indicate actions that are required, as opposed to those that are merely recommended or advisory.

Mandatory instruction signs are often characterized by their octagonal shape and a distinctive color scheme that emphasizes compliance. They are crucial for ensuring safety and efficiency during operations, as they help prevent accidents and miscommunication on the airfield.

In contrast, the other types of signs mentioned serve different purposes: information signs provide general data and details about the airfield, guidance signs offer directional help and aid in navigation, and directional signs give specific instructions for movement or routing. While these other signs play important roles in the overall safety and functionality of the airfield, they do not carry the same level of compulsory authority as mandatory instruction signs do.