An optical approach slope indicator should be installed for helicopter approaches to a heliport — regardless of the presence of other visual or non-visual aids — when one or more of the following conditions apply, particularly during night operations:
a) when a specific approach route must be followed due to obstacle clearance requirements, noise abatement procedures, or air traffic control instructions;
b) when there are no clear visual references in the vicinity of the heliport;
c) when helicopter performance characteristics require a stabilized approach.
