Abstract: Apparatus for aligning an aircraft landing aid projector of the type which comprises a light source located at the focus of a parabolic reflector, a lens mounted coaxially with the parabolic reflector and a filter disposed intermediate the reflector and lens close to the focal point of the lens. The apparatus comprises a base having a surface portion for supporting a projector, a lens for focussing light from the projector onto an image receiving means and means allowing observation of the image receiving means. The filter of a projector is correctly positioned when it appears in focus on the image receiving means.