Illuminated Wind Indicator
Australian regulations require the primary WDI to be white in colour. Any additional windsocks not intended to be illuminated at night are coloured yellow and any additional IWIs are coloured white or another colour that is clearly visible when illuminated.
require that runways served by a non-precision instrument approach (e.g.
must have a windsock at the threshold of the runway, preferably 100
m upwind from the threshold. Nevertheless, aerodromes with runways less
than 1200 m in length need only have one, centrally-located windsock.
(Photo: Phil Vabre/CAHS collection)