I am completely confused by this question. The original printed version made no sense at all and this revised online question still makes no sense.
We are an IFR air transport flight by day. We have a TSO129 and a TSO146. Therefore we are already illegal as we are required to carry two 146 GPS or one 146 GPS and a nav aid. There is no mention of aircraft nav aid equipment in the question.
The answer then states that an alternate is required with a ground based procedure.
Can we please have this question reviewed so that it makes sense? I notice that in the summary of poorly answered questions CASA flags nav aid requirements as being on the list. I’m not surprised given how confusing the text and example questions are on this issue
Regards
Gerard

Gerard
Thanks for your feed-back concerning the question on page 155 of the IREX book. It would not be illegal to fly to Corryong in that aeroplane providing you nominated an alternate. That's the point of the question. Also, there is nothing to stop you flying the RNAV/GNSS approach at Corryong using either the 146 or 129. (once again, not illegal, providing you are carrying the alternate). However, if you do have to proceed to the alternate because the 146 GPS has failed, you must be able to navigate to the alternate by a means other than GPS. That is, either visually or by using a ground based aid. (You can never assume that the 129 will be available).

I do agree that the wording of that question has fallen victim to constant procedural changes and it is overdue for a rewording. We will reword the question. Once again, thanks for your feed back. It is most appreciated.

Thanks. Yes I had misunderstood this requirement and thought it only applied to night VFR flights when they required an alternate. Now I realise that it is possible to legally fly air transport with a a TSO 129 and a Navaid however navigation to an alternate must be by navaid. This is a little unclear in the textbook. When we reach our alternate we can then fly the approach with either the TSO 129 or the nav aid thus giving us redundancy assuming there is a ground based approach. I’m not sure why CASA requires navigation to alternate via navaid if a TSO 129 is good enough to navigate to a destination and fly an approach. Can you elaborate?
I still feel this requirement could be explained a little more clearly in the online text. I did refer to the MOS 91/135 and noticed the 129 grandfathering clause for the TSO 129 which I had not noticed before in part 135.
When I initially read the MOS91 alternate requirements for night VFR I mistakenly thought paragraph 3 ( which required navigation to alternate via navaid ) to only apply to night VFR flight. I now realise it applies day and night if using TSO 129