Modern Avionics and the Instrument Pilot - Part 1 Lateral Navigation and the Flight Director

[wayneda40]

If you’re a current instrument student or an experienced instrument pilot upgrading from a 6 pack… modern glass panels open a whole new world of precision and automation. This short video series is intended to add some clarity to concepts and scenarios for using modern avionics in our instrument procedures. In part 1 we examine lateral navigation plus how to program and monitor the Flight Director/Autopilot combo. Welcome aboard! Wayne, GeezerGeek Pilot

 

[asicer]

At 3:33, you mention flying the GPS to the FAF (NAPPS in your example). However, AC 90-108 Section 8 says:
"An otherwise suitable RNAV system cannot be used for the following:... (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 take that to mean that the "green needle" data needs to be available prior to the FAF (HABUT-GOYED-NAPPS in your example) since those legs are based on the LOC.

Thoughts?

https://www.faa.gov/documentLibrary/media/Advisory_Circular/90-108.pdf

 

[wayneda40]

At 3:33, you mention flying the GPS to the FAF (NAPPS in your example). However, AC 90-108 Section 8 says:
"An otherwise suitable RNAV system cannot be used for the following:... (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 take that to mean that the "green needle" data needs to be available prior to the FAF (HABUT-GOYED-NAPPS in your example) since those legs are based on the LOC.

Thoughts?

https://www.faa.gov/documentLibrary/media/Advisory_Circular/90-108.pdf

@asicer, indeed you're correct regarding the advisory, and my narrative at that point was I believe consistent... "As we approach the segment leading to the FAF, we transition to the green needles for the ILS". I believe that's also clear by the graphic that shows the segment leading to the FAF (GOYED-to-NAPPS) in dashed magenta ("reference only") and solid green. In fact, the navigators I noted in the video auto-switch from magenta to green needles on the segment leading to the FAF.

Thanks for watching and for checking in on this,
Wayne

 

[John Collins]

There isn't a regulation per say in directly dealing with the issue of flying localizer courses, but there is plenty of guidance in the AIM and the current AC 90-108. This AC is going to be superseded eventualy by what is now a draft 90-119. The last draft I saw of AC 90-119 says this:

11.4.3 Unauthorized uses of RNAV Systems.

11.4.3.3 Localizer Course. To navigate a localizer final approach course.

AFMS limitations sections are specified in regulations and override FAA guidance such as contained in the AIM or an AC if they differ from guidance. Here is the current wording in the GNS 430W/530W and GTN series navigator AFMS.

Navigating the final approach segment (that segment from the final approach fix to the missed approach point) of an ILS, LOC, LOC-BC, LDA, SDF, MLS, TACAN approach, or any other type of approach not approved for GPS, is not authorized with GPS navigation guidance.

What is in the AIM is not the most current thinking of the FAA but the guidance will take some time before it reflects what is part of the new draft AC. The wording in the AFMS was updated on the GNS series in 2013. Regardless, AFMS rules!

So if the AFMS doesn't require using the green needles until on the final approach segment of an ILS, then in spite of AC and AIM guidance to the contrary, that wording overrides the guidance.

 

[wayneda40]

…

So if the AFMS doesn't require using the green needles until on the final approach segment of an ILS, then in spite of AC and AIM guidance to the contrary, that wording overrides the guidance.

@John Collins, solid and up-to-date info… thanks!
Wayne

 

[John Collins]

Nice video as usual. Even though using the green needles on the ILS is only required for navigating on the final approach segment, G1000 and other Garmin GPS systems auto switch the GPS magenta needles to the green needles as soon as the FAF is the active fix, which is usually once the intermediate leg leading to the FAF becomes the active leg. It makes sense to do it so that the green GS is intercepted.

 

[asicer]

@asicer, indeed you're correct regarding the reg, and my narrative at that point was I believe consistent with the reg... "As we approach the segment leading to the FAF, we transition to the green needles for the ILS". I believe that's also clear by the graphic that shows the segment leading to the FAF (GOYED-to-NAPPS) in dashed magenta ("reference only") and solid green. In fact, the navigators I noted in the video auto-switch from magenta to green needles on the segment leading to the FAF.
View attachment 103535
Thanks for watching and for checking in on this,
Wayne

You still have HABUT-GOYED in solid magenta and this course is defined by a LOC.

What is in the AIM is not the most current thinking of the FAA but the guidance will take some time before it reflects what is part of the new draft AC. The wording in the AFMS was updated on the GNS series in 2013. Regardless, AFMS rules!

I tend to choose the more conservative, which is to switch when the localizer comes alive according to AC 90-108. But I suppose at this point it's just splitting hairs. When AC 90-119 is finalized, I'll start switching at the FAF. And I look forward to doing so!

 

[wayneda40]

You still have HABUT-GOYED in solid magenta and this course is defined by a LOC.

I tend to choose the more conservative, which is to switch when the localizer comes alive according to AC 90-108. But I suppose at this point it's just splitting hairs. When AC 90-119 is finalized, I'll start switching at the FAF. And I look forward to doing so!

As John noted, with the G1000/GTN navigators the navigator does an auto-switch from magenta to green (and auto-sets and auto-swaps the ILS frequency!). One less chance for me to make an error (even though I must be the only person to have ever forgotten to switch to "VLOC" on a GNS430 ).

 

[John Collins]

You still have HABUT-GOYED in solid magenta and this course is defined by a LOC.

Either navigation source is allowed for this leg.

I tend to choose the more conservative, which is to switch when the localizer comes alive according to AC 90-108. But I suppose at this point it's just splitting hairs. When AC 90-119 is finalized, I'll start switching at the FAF. And I look forward to doing so!

It is OK for you to be conservative, but it is helpful to understand the difference between guidance and a regulation. The regulations permit GPS to be used on the segment between GOYED and NAPPS, at least on the GNS and GTN series Garmin navigators.