What is the role of wing inspection lights?

The role of wing inspection lights is primarily to aid in checking for ice formation on the wings of an aircraft. This specific function is crucial during pre-flight inspections and while flying in conditions that may lead to ice build-up. Ice on the wings can significantly affect the aircraft's performance, including lift and stall characteristics, making it essential for pilots to visually inspect the wings to ensure they are clear of ice before takeoff and during flight operations.

The other options refer to different functions that do not align with the specific purpose of wing inspection lights. For example, signaling aircraft on approach is generally done through different lighting systems on the aircraft and on the ground. Illumination of the cargo hold is managed by separate lighting designed for that area, while altitude indication is provided through instruments within the cockpit rather than external lights. Therefore, the focus of wing inspection lights is distinctly on enabling pilots to ensure the wings remain safe and operationally effective.