A gas turbine engine has a casing component, such as a mid turbine frame system, which includes an outer case surrounding a spoke or strut casing. Then, the longitudinal length of the lamp is shortened so as to attempt to make the lamp compact in size by inserting a light source bulb into a reflector from a side of an optical axis Ax. The intermediate rail further includes inner rolling surfaces for the rolling elements that face the rolling surfaces of the guide rail.