AS 3891.2:2018 Air navigation—Cables and their supporting structures—Marking and safety requirements
2.3.1 Design
Aircraft warning markers for cables shall meet the following design requirements:
(a) Planar with minimum area of 0.09 m2 and encompassing a circular area with a minimum diameter of 200 mm; or
(b) If required to be visible from any angle on a plane horizontal to the marker, a shape with a minimum projected area of 0.07 m2, and a minimum dimension through the centre of area of at least 200 mm; or
(c) Cylindrical with a diameter of at least 180 mm, and a length of at least 300 mm; or
(d) Any other aircraft warning marker design that is able to prove its operational visibility to an equivalent performance. These markers shall be visible under anticipated typical atmospheric and meteorological conditions from a minimum distance of 400 m by a person with a vision standard that is conformant with CASA pilot medical standards.
NOTE The visibility requirement of 400 m was calculated by using the speed of a high performance aerial application aircraft (travelling at 140 kn or 72 m/second), with a nominal pilot and aircraft reaction time of 4s (=288 m), plus a safety buffer to equal 400 m.
2.3.2 Installation Aircraft warning cable markers shall meet the following installation requirements:
(a) Orientation 一The positioning of the marker(s) shall ensure that sufficient markers remain visible throughout the approach flight path such that the pilot has adequate advance indication of the presence of the cable.
(b) Spacing and location – Markers shall be spaced to allow the pilot to assess the cable direction at all times during the approach. Markers shall be placed mid-span unless there are particular local circumstances identified in the consultation process that warrant a different location or multiple markers.
(c) Authorization 一Aerial warning markers on cables shall only be installed, maintained or removed in consultation, agreement and with the approval of, the cable owner by an appropriately trained and authorized person.