ATC AU-501
1.2 Altimeter Setting Rules
1.2.1.2 For ALL OPERATIONS at or below Transition alt (in the alt setting region), (see fig 1 pg AU 502), the alt reference will be:
a) the current Local QNH of a station along the route within 100nm of the a/c; or
b) the current Area Forecast QNH IF the current Local QNH is not known.
the above means on clb and desc.
AU-501
1.2.3. Local QNH
1.2.3.1. Local QNH, whether providedby ATS, AWS, or TAF or by using the alt subscale to indicate airfield elevation, is used as shown in figure 1. (AU 501)
In addition see MET AU-37, 4.3.1 & 4.3.5 (.......Therefore QNH from these AWSs may be used in accordance with TERMINAL INSTRUMENT APPROACH/TAKEOFF PROCDEDURES, QNH SOURCES.
Almost finally, see TERM AU-29, 5.3 QNH SOURCES, 5.3.1. Prior to passing the IAF, the pilots are required to set either,
a) the actual aerodrome QNH from an approved source, or
b) the forecast Terminal QNH, or
c) the forecast area QNH
Using common sense, does anyone think that Area F/cast QNH is more valid than a "live" actual qnh from within 100nm and is no more than 15 mins old, when the Area F/cast Qnh within that area only has to be within 5mbs and covers how many sq kms, and some think 100nm is too far. ICAO reference to distance and qnh for Oz has nothing to do with us.
WALLY, there is no definition of 'actual' qnh in Jepps that I can find which is why is isn't in caps, other than a dictionary definition of actual (actual |ˈak ch oōəl|
adjective
1 existing in fact; typically as contrasted with what was intended, expected, or believed : the estimate was much less than the actual cost | those were his actual words.
That means real, live, not f/cast!