RNAV for conventional approaches

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CerroTorre

Pre-takeoff checklist
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CerroTorre
So I've got a little lack of clarity on exactly what is allowed when substituting (for example) a TSO 145c WAAS GPS for conventional navigation. And specifically how I'd explain and reference it to someone. I think my confusion stems from AC 90-108.

AIM 1-2-3 (a) (2) "For example, if equipped with a suitable RNAV system, a pilot may fly a procedure or route based on operational VOR using that RNAV system without monitoring the VOR".

AC 90-108 USES OF SUITABLE RNAV SYSTEMS NOT ALLOWED BY THIS AC
b. Substitution on a Final Approach Segment. Substitution for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment.
c. Lateral Navigation on LOC-Based Courses. Lateral navigation on LOC-based courses (including LOC back-course guidance) without reference to raw LOC data.

I know I'm likely missing some obvious details... Thanks all.
 
More specifically, when and for what legs of a "conventional (non-precision) approach" am I allowed to solely rely on the TSO-145 GPS? When am I allowed to only fly the Initial and Intermediate segments? When do I have to "actively monitor".

ex. VOR-A into KRDM and the ILS 23 (initial and intermediate segments) into KRDM

I THINK I know the answers to at least some of these, but need some more heads to bounce these things off to solidify it for myself.

Thanks again.
 
You can use VORs fixes en route and may fly an procedure based on ground nav aids until the FAF. When you are are begin the final approach segment you have to use the nav system specified in the approach title.

The VOR is the FAF on the VOR-A and VERNN on the LOC/ILS.
 
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CerroTorre said:
More specifically, when and for what legs of a "conventional (non-precision) approach" am I allowed to solely rely on the TSO-145 GPS? When am I allowed to only fly the Initial and Intermediate segments? When do I have to "actively monitor".
Click to expand...
'Allowed' is anything and everything other than lateral guidance on the final approach segment.
'Actively Monitor' is lateral guidance on the final approach segment of a VOR or NDB approach.
 
Thanks both.

So, AIM 1-2-3 and AC 90-108 are not contradictory. Rather AC 90-108 specifically clarifies that the RNAV units simply cannot be used past the FAF for lateral guidance (but can still be used as DME for step downs, etc). Is that a correct assessment?

I think this is one of those things that throws my brain for a loop when I get into the particular way that regulations are written. The more I chase a thread that I thought I understood, the more convoluted it becomes. A regulation might be buried beneath two or three "if/then" statements that require parsing to get to the final answer.

Regardless, I think I understand this one. Thanks again.
 
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This is what's wrong with POA these days. Nothing but bullying chasing away a new user. :mad:
 
CerroTorre said:
So, AIM 1-2-3 and AC 90-108 are not contradictory. Rather AC 90-108 specifically clarifies that the RNAV units simply cannot be used past the FAF for lateral guidance (but can still be used as DME for step downs, etc). Is that a correct assessment?
Click to expand...
Well, you can find a few contradictions here and there. Remember that the AC is 11 years old at this point. The AIM is amended regularly and is the more up-to-date FAA guidance on the subject.
 
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