reply to Mars
"I think you have confused some on this thread - the equipment you mention is a standard RADALT with an AVAD: two settings are available; that which is set by the pilot; and the factory preset warning (in the UK set to 100'). The first gives "check height" and the second "100 feet" (or whatever is the factory preset)."
Mars the AVAD system we have works through the RADALTS. The "check height" aural warning occurs when the helicopter decends through the lowest RADALT bug setting (set by either pilot from 0 to 2500' on our radalts) the 100' aural warning works when the helicopter decends through 100' on the radalts.
The AVAD system can be u/s and the RADALT's will still work normally. You may or not get the check height or 100' aural warnings depending on the problem with the AVAD system.
In AUS you can go DAY VFR OFFSHORE with either Radalts or AVAD U/S. NVFR or IFR depends on clients and other considerations.
Anyway back to the original thread issue, is there any news on the ATSB investigation?