Night IFR below LSALT
Just curious as to what the requirements are for IFR flight below LSALT at night?
Saw an aircraft flying around a city south of Sydney (which has a large steelworks) a couple of weeks ago, at night, at 1500 feet, below the height of the moutains (2000 feet) which are 2 miles to the west of the city and conducting continous orbits over the town, considering the LSALT to the north of that aerodrome is 3600 feet.
I believe the aircraft has a contract requirement to always flight plan IFR and was not conducting any search and rescue at the time.