G'Day BT, just wondeing, If you are creating a LSALT using GPS receiver and you are going to a airport with no instrument approach except a RNAV and you are TSO-C145a with fault dection, do your lines come into the Airport at 10.3 degrees or create a semi circle? Also what would you do if it had no RNAV but you were tso-c145a? and TSO-C129?

Cheers, this one is confusing me
Brian

The converging 10.3° lines are used when the destination has a ground-based aid such as ADF or VOR. Ground aids are of no concern to RNAV GNSS receivers. The lowest safe is based on the area withing 7nm either side of track until abeam the destination, then a semicircle with a radius of 7nm centered on the destination plus a 5nm buffer [AIP GEN 3.3 para 4.9].

I'd like to ask a question based on this initial topic, if that's ok.

Since 26 May 2016, the AIP GEN changed, with GEN 3.3 Section 4 being amended with introduction on RNP2 operations.

GEN 3.3 - 4.8, For other Area Navigation Operations... the lines drawn from the departure point must not be less than 15-degrees...

So this means it USED to be 10.3 but NOW it is 15? I just want to make sure I am interpreting this correctly...

This flip-flopping of rules is beginning to frustrate me. Thanks in advance. Howie.

Hi Howie,

Correct, the splays go out at 15 degrees for other RNAV systems. The 10.3 degree splays are for use of a radio navaid. Good luck with measuring 10.3 degrees by the way

GEN 3.3, 4.7 states the area to be conisdered is a 10km wide sausage between circles of 5nm radius based on the orgin and destination aerodromes under the RNP2 specification. This does not have a 5nm buffer applied to it.

GEN 3.3, 4.8 refers to the15 degree splays out to various distances depending on the RNAV equipment you are using.

Cheers,

Rich

Thanks Rich,

Could you please verify that 4.7 is indeed 10km? I read it to be a 5NM 'sausage'...

"... within an area of 5NM surrounding and including the departure point, the destination and each side of the nominal track."

-Howie