An optical approach slope indicator must be installed for approaches to a heliport, regardless of the presence of other visual or non-visual aids, when one or more of the following conditions occur, especially at night:
a) the need to follow a specific route due to obstacle clearance, noise abatement limitations, or air traffic control procedures; b) the absence of clear visual references in the vicinity of the heliport; c) helicopter characteristics that require a stabilized approach.
