Its not that hard to look it up yourself Dick its called the internet:
9.1C A turbine-engined aeroplane that:
(a) has a maximum take-off weight of more than 15 000 kg or is carrying 10 or more passengers; and
(b) is engaged in RPT, or charter, operations;
must not be operated under the I.F.R. unless it is fitted with:
(c) an approved GPWS that has a predictive terrain hazard warning function; or
(d) if paragraph 9.1CA applies — a GPWS that meets the requirements of Civil Aviation Order 108.36 (a CAO 108.36 GPWS); or
(e) if the aeroplane has a maximum take-off weight of 5 700 kg or less, but is carrying 10 or more passengers — a TAWS-B+ system.
And the US requirement:
c. § 135.154 states that no person may operate a turbine-powered U.S.-registered
airplane configured with 6 to 9 passenger seats, excluding any pilot seat, unless that
airplane is equipped with an approved terrain awareness and warning system that meets
the requirements of Class B equipment of TSO-C151a. It also states that no person may5/22/00 AC 25-23
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operate a turbine-powered U.S.-registered airplane configured with 10 or more passenger
seats, excluding any pilot seat, unless that airplane is equipped with a terrain awareness
and warning system that meets the provisions of Class A equipment of TSO-C151a.
So my question again is why aren't you agitating for worlds best practice with equipment that can save lives (i.e Benalla) but instead focusing on ATC procedures?
You state that "you probably gave up", but from the way you have bombarded prune with your crusade against the "half wound back system" that doesn't seem to be your style.