A helmet mounting for optical combiner (50) for a HMD has a pivoted mounting arm (60) for the optical combiner to be movable between an operational position in a line of sight, and a retracted position displaced out of the line of sight. A translation mechanism (100) provides translation of the optical combiner along the line of sight. A driving lever (30) causes the displacement of the mounting arm between the line of sight and the retracted position, and with a second motion of the lever, causes the translation of the optical combiner. By having the same lever coupled to both the mounting arm and the translation mechanism, the relatively complex combination of displacement and translation movements of the optical combiner can be reduced to a simpler movement, easier for a user such as a pilot to use even when under stress in a busy and cramped cockpit environment.