AS 3891.2:2018 pdf free.Air navigation—Cables and their supporting structures—Marking and safety requirements Part 2: Low level aviation operations.
2.5 Aircraft warning markers — Ground-based
2.5.1 Design
Ground-based aircraft warning markers shall meet the following design requirements:
(a) 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 con formant to CASA pilot medical standards.
NOTE The visibility requirement of 400 rn was calculated by using the speed of a high performance aerial application aircraft (travelling at 140 kn or 72 rn/second), with a nominal pilot and aircraft reaction time of 4 s (=288 m), plus a safety buffer to equal 400 m.
(b) Ground-based markers may include strobe lights, truncated cones or pyramids.
If strobe lights are used, they shall be high in intensity, omni-directional, white flashing lights of at least 2500 cd. The flash rate shall be between 40 and 50 flashes per minute.
(c) If truncated cones or pyramids are used, they shall be in the form of a truncated cone or truncated square pyramid and meet the performance standard in Item (a).
NOTE Translucent material can be used and the structure can be ventilated in such a way as to reduce wind pressure.
2.5.2 Installation
Ground-based aircraft warning markers are intended for installation directly beneath an overhead cable to provide an indication of the direction and location of the cable.
Ground aircraft warning markers shall be placed at intervals not exceeding SO m.
2.6 Aircraft warning markers — Aerial inspections
2.6.1 General
Overhead crossing aircraft warning markers shall be used to indicate the proximity of a cable of one circuit crossing above a cable of another circuit that is subject to aerial inspection.
2.6.2 Design
Overhead crossing aircraft warning markers shall meet the following design requirements:
(a) Be circular in shape and not less than 300 mm in diameter.
(b) The colour used shall be Canary Yellow, as specified in Clause 2.2.2.
2.6.3 Installation
Aircraft warning markers for aerial inspection of powerlines shall be placed as follows:
(a) At the top (peak) of the support structure that supports the lower cable circuit subject to aerial inspection.
(b) On the second and third structures from the in-span circuit crossing location.
(c) On either side of the crossing.
(d) The overhead crossing markers shall face away from the in-span crossing location, such that they provide proximity warning to aerial inspection aircraft undertaking lower circuit inspection and operating towards the in-span crossing location.AS 3891.2 pdf download.