ATC light gun signals are particularly useful in what situation?

The use of ATC light gun signals is particularly suitable in situations where radio communication is unavailable. This includes instances such as radio failure or when pilots cannot establish contact with air traffic control due to various circumstances. The light gun serves as a visual communication tool, allowing controllers to convey essential instructions to pilots through a series of colored light signals. This system ensures that safety and operational control can be maintained even in the absence of standard radio communication, making it a critical resource in emergency situations. In contrast, options like maintenance checks of aircraft, routine weather reports, and turbulence do not directly relate to the need for visual signals in lieu of lost radio contact, which is why they are not the correct context for the use of light gun signals.