EDIT: Apologies to all, was meant to post this in the IREX forum

Hi Everyone,

I am currently studying IREX and hope to have it finished in the next few weeks, however as the May 26th (Today) transition changes OZY's equipment there is one thing I can't rap my head around.

Since being upgraded to dual TSO-C146a receivers VH-OZY no longer requires an alternate for an aerodromes with ground based aid as it satisfies the RNAV-GNSS requirements which makes enough sense,

Yet in AIP ENR 1.1 Para 58.3.1 an alternate is still required for RPT and Charter Flights unless the destination is served by two seperate radio navigation aids, or the aircraft equipped has dual receivers for that one particular aid - this is the 26th May 2016 supplement as well.

My interpretation of this is that Radio Navigation Aids refers to VOR/NDB/DME and that the AIP is contradicting itself, and even with dual C146 receivers an alternate is still required. If anyone could shed some light on this and show what I've missed that would be greatly appreciated!

Cheers

Gidday Wobbles
Your interpretation is correct. When the AIP refers to 'Navigation Aids' in AIP ENR 1.1 para 58.3.1, it means ground-based navigation aids (ADF, VOR or DME). Any satellite-based system is referred to as 'GNSS'. CASA is actually well overdue to clarify the the many examples of confusing terminology that are creeping into the documents. It's the result of piece-meal amendments to text that was originally written decades ago.

Bob

Hi Bob,

Thanks for the explanation and clarification. This still leaves me confused however as it means that we will still require an alternate no matter what, even for private operations when no ground station is available.

In what scenario now would the twin C146a receivers make a difference if we still require an alternate for all aerodromes that have a published RNAV approach but no ground station available? We can plan to use the RNAV but that makes no difference to the situtuation if an alternate is required regardless.

In short does this change mean that the only real exam questions that are different is the lowest possible MDA since we can now factor in these approaches for our arrival?

The reason I ask is that in the IREX forum sticky regarding the change the following is said -
Would the above mean that if the only approach available is RNAV (Therefore no ground station) an alternate is not required?

Thanks for your help

Wobbles

AIP GEN 1.5 para 2.1 says that a CHTR or RPT aircraft must be equipped with either:
One GNSS of TSO C129 or higher, plus one ADF or one VOR.
or
Two GNSS TSO C145 or C146. (if you have this, you don't need and ADF or a VOR).

AIP ENR 1.1 para 58.3.1 says in effect that an IFR CHTR flight must be capable of two 'shots' at getting visual on an approach. (If one airborne aid fails, there still must still be an approach available).

If you accept this philosophy, a CHTR flight with two GNSS TSO C145 or higher would not need an alternate even if the only approach available is an RNAV (GNSS) approach. However, if you were a CHTR flight, and had only one GNSS TSO C145 or higher, you would still need a ground-based aid to avoid the alternate requirement for aids.

However, a PVT or AWK flight needs only one GNSS TSO C145 or higher to avoid the alternate requirement for aids.

Bob