Only a guess at this one but if flying at an approved low altitude they may have permission to switch off all lights. They have to maintain constant contact with Perth ATC to do so.
I remember an incident in Sydney where their Police chopper was being shot at so they were allowed to swith off all lighting and mainting a search with the FLIR.
they did this when they were chasing that motorbike in Belmont last week.They had no spotlight or nav lights.And since then i've noticed they seem to fly around alot with no lights on at all.It certinly is strange.
Guys, from being a fly boy at Jandakot - I have spoken to my instructor who knows all the crew for Polair 61 & 62 - and turning their nav lights are a part of the job to go "invisible" at night - They do get extra special clearence from Perth Tower - and go on a special Transponder code.
I think it's a great idea - especially when Polair is just cruising over trouble spots - so the badies can probably hear the chopper - but can't see it at night - Which isn't a bad tactic - but they do turn them back on - when they head back to YPJT (Jandakot).