Hi,

Question 17 Revision Exercise 4

You plan to depart Blackall on runway 06 for an IFR flight to Longreach. You are flying VH-OZY and you plan to return to Blackall in the event of an engine failure in IMC after take-off. Assuming you are current on all instrument approaches for Blackall, and the actual QNH is not available from an approved source, the meteorological minima that apply to the take-off are-

A 300ft AGL cloud base and visibility of 2km
B 2700ft AMSL cloud base and visibility of 5km
C 1520ft AMSL cloud base and visibility of 3.4km
D 482ft AGL cloud base and visibility of 2.7km

Blackall only has NDB and RNAV procedures. I am current on all procedures but I am flying OZY which does not have a GPS cert for the RNAV procedure so I chose the NDB minimums C.

In the answers you say D - the RNAV minimums. Is this correct or an error?

Cheers,
Lindsay

Lindsay

AIP GEN page 17, Table, second row para 4 seems to be a recent addition. It used to say that the restriction on TSO 129 GPS was for satisfying the flight planning alternate requirements. Now it is saying that you must always have an alternate approach available whenever you use a 129 GPS for an RNAV GNSS approach. No doubt you realise that this does not mean that a 129 GPS is not certified for the approach procedure. It simply means that if you do an approach with a 129 GPS, you must have another option as a back-up.

I agree with your answer and I have changed the question/answer in the next print of the book.

Thanks for your feed-back

Bob

Thanks Bob,

I was actually confused about the TSO 129 GPS. I went all the way through the book thinking you could not use it for an RNAV GNSS approach! Now I see that it just effects the alternates requirements. I got lucky with the AIP ammendment!

Cheers,
Lindsay

Hi Bob,

With this IAP change, does this mean that I could now "plan" an IFR charter to somewhere like Blackall without an Alternate? Given two independent aids (NDB / Rnav)

Cheers
Gareth

No. What the AIP is saying is that when it comes to alternate planning, if you only have a 129 GPS, you must always cross it off the list of available aids. However once you get to the destination, there is nothing to stop you from doing the RNAV GNSS approach since you would be carrying the alternate if something went wrong. You're still safe.

Many students form the opinion that you cannot do an RNAV GNSS approach with a 129 GPS. That's not correct. There is no difference between a 129 and a 145/6 GPS when it comes to accuracy. The differentiation is made on the grounds of integrity. The instrument is perfectly OK as far as accuracy is concerned, so you can do an approach with no worries. While it's working, it works as good as any GPS. However, you can't use it as the ONLY means of getting down because it is considered more likely to lose signal quality in some circumstances.

Whenever you do an RNAV GNSS approach with a 129 GPS, you must always have a 'plan B'. So you couldn't take-off from Blackall and plan to return in the event of an engine failure unless the weather was above the NDB minima.

That's cleared things up.

Thanks for your quick reply

Cheers
Gareth