AIM Change - Use of GPS inside the FAF of a conventional approach

[midlifeflyer]

Especially in aircraft equipped with an HSI or FMS, many pilots have flown (and some CFIIs have advocated flying) the final approach segment for a non-GPS approach with the GPS source feeding Nav 1, while monitoring the VOR "raw data" in Nav 2. Now, in a May 26, 2016 update to the AIM the FAA specifically approves the practice, at least for VOR, NDB and TACAN approaches.

As the new Note 5 to AIM 1-2-3 puts it:

Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID monitored for final segment course alignment.​

I don't know for sure but have heard this was a concern for some Part 121 an 135 operators which rely heavily on FMS — a concern over a possible grey area over which nav display is "primary," especially when GPS is feeding the FMS and autopilot. Seems to be a clarification more than anything else, but it's always nice to see a possible grey area disappear - in a good way.

This and other changes in the May 26 update may be viewed at http://1.usa.gov/1TESEeB

 

[aterpster]

Especially in aircraft equipped with an HSI or FMS, many pilots have flown (and some CFIIs have advocated flying) the final approach segment for a non-GPS approach with the GPS source feeding Nav 1, while monitoring the VOR "raw data" in Nav 2. Now, in a May 26, 2016 update to the AIM the FAA specifically approves the practice, at least for VOR, NDB and TACAN approaches.

As the new Note 5 to AIM 1-2-3 puts it:

Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID monitored for final segment course alignment.​

I don't know for sure but have heard this was a concern for some Part 121 an 135 operators which rely heavily on FMS — a concern over a possible grey area over which nav display is "primary," especially when GPS is feeding the FMS and autopilot. Seems to be a clarification more than anything else, but it's always nice to see a possible grey area disappear - in a good way.

We were doing exactly that in the 767 circa 1985.

 

[kgruber]

We were doing that 25 years ago on FAA 135 check rides with the Gold Crown KNR-665A. The FAA had no idea how the "box" worked, and were clueless how we flew an NDB approach so accurately.

 

[kayoh190]

Wow - didn't realize this was a grey area. As others noted, every commercial operator I've worked for (including my current one) uses the FMS for guidance on VOR or NDB approaches, with the PNF monitoring with green needles. Nice to see some actual language, though.

 

[Everskyward]

I remember years ago there was a bit of a controversy between my employer and a training provider. The instructors and examiners encouraged us to set up NDB approaches with the GPS or FMS, but not all of our airplanes had the capability, so the DO wanted us to be doing NDB approaches without other aids.

 

[aterpster]

I remember years ago there was a bit of a controversy between my employer and a training provider. The instructors and examiners encouraged us to set up NDB approaches with the GPS or FMS, but not all of our airplanes had the capability, so the DO wanted us to be doing NDB approaches without other aids.

I guess it depends whose on first, so to speak. On my 767 rating ride in the sim I did it to ace the required NDB approach, with an ops inspector observing.

 

[midlifeflyer]

Wow - didn't realize this was a grey area. As others noted, every commercial operator I've worked for (including my current one) uses the FMS for guidance on VOR or NDB approaches, with the PNF monitoring with green needles. Nice to see some actual language, though.

There are some operators specifically permitted to do this under OpSpecs.

Plus, I used to say "'I don't understand' doesn't mean it's grey" but have come to the conclusion that "grey" is subjective. What is pretty clear to one person may be completely unclear to another. IOW, grey is in the grey matter of the beholder.

To the extent operators were concerned about it, it's always good to get some clear direction.

 

[fiveoboy01]

Not that I will fly a lot of VOR approaches in the future but I wa doing this during instrument training.

VLOC on the #1 head, CDI screen on the 430W.

 

[NoHeat]

I fly a VOR approach into my home drome, and I am happy to learn this. My #1 Garmin navigator nagged me to switch from GPS to VOR as I approached the FAF and so I reluctantly did. Now I know I can just ignore the nagging and do as the OP said.

 

[Gucci Pilot]

I guess I can see how it would be grey. In the Air Force, if I did this on a VOR approach and had the CDI coming off the GPS and the bearing pointer set for the VOR, I can think of quite a few pilots that would throw. It would take some arguing but I think I could persuade them that it is legal. Now since the bearing pointer is the only source of guidance on the NDB, it is pretty standard to have the CDI set to the GPS and the bearing pointer set to the NDB.

 

[fiveoboy01]

I fly a VOR approach into my home drome, and I am happy to learn this. My #1 Garmin navigator nagged me to switch from GPS to VOR as I approached the FAF and so I reluctantly did. Now I know I can just ignore the nagging and do as the OP said.

According to the cite in the OP, you can't do that unless you're monitoring the VOR with another CDI.