The more I think about it the more i tend to see the CH47F as a viable replacement for DHC-4 Caribou.
With a fleet of 18 Chinook airframes under a joint command structure i believe it is a win/win situation for the RAAF/Army/RAN, with the RAAF using C130J Hercules aircraft to bring in supples and logistic needs for the ADF.with an additional purchases of Hercules aircraft to replace the aging H model and possibly two more C17 to ease the burden of the current fleet.
C27J Spartan i don’t think is a necessity in a RAAF colours as J Hercules are capable off doing the job better and more efficiently than the Spartan.
I do agree that more CH-47's are needed for the ADF. However, given that Army is the current CH-47 operator, and has been since the RAAF gave up rotary wing ops, I see no advantage in creating a joint command structure to operate them. If some Chinooks were operated by the RAAF and some by Army and more were needed, then some form of joint structure might make sense. IMO to set something like this up would just duplicate effort and personnel between the RAAF and Army.
In terms of the C-130J being more efficient than the C-27J Spartan, that is true, just not in all cases. A C-130J can carry ~twice the load of a C-27J, and convey it ~twice the distance. However, if the mission profile fits within the weight/range limit of the C-27J then it is more efficient to utilize a Spartan than a C-130J. Given RAAF Hercs have flown enough transport missions half empty to have had people comment on about it, having a somewhat smaller transport that can transport small loads more efficiently than a C-130J but otherwise has much in common with the new Hercs seems sensible.
The question then becomes what sort of mix should be acquired. The ADF currently has (or is receiving) or had, 7 CH-47 Chinooks, 12 DHC-4 Caribou and 12 C-130H Hercules. The Caribous are either already grounded or not all available for operations if not yet retired. Some have suggested straight replacements of a dozen each C-27J Spartans and C-130J Hercules II's, others have suggested more of a split airfleet mix, with 18 Spartans and 6 C-130J's to replace the Caribou and C-130H Hercs.
While using the CH-47 as a 'bou replacement has been suggested, I am not certain that the employment method Army has for the Chinook would deliver service comparable to that of the 'bou. A Caribou travels about 100 kts faster than a CH-47, but carries ~1,500 kg less and can only cover ~half the distance. Therefore the question becomes, what does the ADF want/need the 'bou replacement to do?
I doubt those that know can/will say anything, but it is a good question to ask.
-Cheers