https://www.casa.gov.au/publications...alian-aircraft
All pilots must conduct in-flight fuel management, including in-flight fuel quantity checks at regular intervals.When conducting these checks, you may discover that you would be landing at your original planned destination without sufficient fuel, that is, your fixed fuel reserve remaining.If this occurs, make an alternate plan to land safely with sufficient fuel at a different location than you had originally planned. Your new safe landing location will depend on your aircraft capabilities and the conditions. In some instances, it may not even be an aerodrome but could be a field.However, if a safe landing location is not an option and you are landing with less than your fixed fuel reserve, then you must declare Mayday Fuel.
My bolding
You have to be joking? Who in their right mind is going to call a MAYDAY if they believe they might be 5 or 10 minutes short on their planned fixed reserve? And just who is going to risk their aircraft by landing in a field just short of their destination?
The proposition that pilots are required to put out a MAYDAY if they expect to arrive with less than the mandated reserves, but a MAYDAY FUEL is to be treated differently (by those on the ground) from other MAYDAY's in that "a declaration does not automatically mean that emergency services will be mobilised". A MAYDAY call is supposed to mean "drop everything and pay attention, lives are at risk". A PAN call is what is used for "I have a problem and may need assistance". I think it's a very bad idea to be telling emergency services some MAYDAYs warrant a response and others don't.
A quick check of the ATSB stats show that the majority of fuel incidents relate to fuel starvation (fuel mismanagement) rather than exhaustion (empty tanks).
Obviously there are people in CASA that believe this is a safety issue. What is the problem they are trying to fix?