25 mile MSAs & the 10 mile MSAs within...

[OzExpat]

Nurries mate. Over the years, I've seen a lot of confusion on this and it's primarily created because ICAO Documents are always based on one, or more, of the Annexes. As ICAO says, the Documents contain technical information that is beyond the scope of the Annex (or words to that effect).

Thus, the inevitable result is that people erroneously associate Documents with Annexes in the need to file differences. I get confused just talking about it!

[JAR]

I haven't read all the above, but 25 nm MSAs are based on IAF and 10nm on the aerodrome. Therefore if IAF is a VOR located some way from airport then MSAs will be different.

[OzExpat]

Not sure that I'd agree with that JAR. For a start, the 25 MSA isn't necessarily based on the IAF - to make such an assumption could give you a real "bad hair day". As with the 10 MSA, the 25 MSA is based on whatever the chart says it's based on.

[JAR]

From Jeppeson MSA is defined as "....within 25 nm radius from the navigational facility upon which the MSA is predicated."
Granted, not always, but more often than not, the IAF.

[NOtimTAMs]

.....except for those with GNSS RNAV approaches only, where the MSA is centred on the ARP - don't know if an ARP counts as a "navigation facility", but.