CDI requirement when using GPS

Chief Captain

Chief Captain

Well-Known Member
The G1000 thread below got me thinking...

On the G430/G530, is the moving map suitable for navigation?

I say no, the CDI must be used, because the map is just an aid to situational awareness; but I can't seem to find a concrete reference for that. Any help?

Also, let's say the panel mounted CDI fails, would the CDI on the first NAV page of the display be considered appropriate for course guidance?
 
Map is only for reference officially but quite useful for initially turning 'direct'.

I'm going to leave the CDI on the display question to somebody else... I've got an opinion, but I'll let others more familiar with that unit comment first.
 
I have literally seen a CDI show a "Fly left" indication, yet have the line on the moving map be to the right of the aircraft when closely zoomed in. Go with the CDI.
 
are we talking about a specific type of approach? or just in general cruise flight? if you're on an ILS, you have to use the CDI and it must be receiving it's info from the ILS.
if you're in cruise flight going direct somewhere using GPS, the CDI needle (if set to the correct OBS) should read identical to the CDI needle on the first page of 530 or 430. As far as just looking at the GPS screen goes, use the little CDI rather than the map. It SHOULD read the same, but stick to the CDI. also the more you zoom in, the more precise the map. (doesnt mean it's any more accurate, just more precise)
 
A GPS certified for IFR operations must be capable of driving a conventional CDI (e.g., on an instrument, in the instrument panel) located within full view of the pilot.

So no, the moving map doesn't suffice, legally speaking. And no, the CDI on the 430/530 does NOT suffice for approach guidance. If you lose your in-panel CDI, you are not *legally* permitted to shoot an instrument approach.
 
Interesting...when I was flying the Avidyne Entegra IFR, the procedure for PFD loss was to shoot a GPS approach using the 430's CDI. We did this all the time.
 
My point is that using the 430's built-in CDI is the Avidyne/Garmin procedure for PFD loss while IFR. This is demonstrated on checkrides for partial-panel instrument approaches. I'm guessing that examiners would've gotten a bit angsty if regs were being busted every time this is done on a checkride...
 
pwttogfk said:
My point is that using the 430's built-in CDI is the Avidyne/Garmin procedure for PFD loss while IFR. This is demonstrated on checkrides for partial-panel instrument approaches. I'm guessing that examiners would've gotten a bit angsty if regs were being busted every time this is done on a checkride...
Click to expand...

Ah, got it. Sorry, lol. That's interesting, actually - do you have instrument check rides that operate under IFR (in IMC)?
 
Autothrust Blue said:
Ah, got it. Sorry, lol. That's interesting, actually - do you have instrument check rides that operate under IFR (in IMC)?
Click to expand...

I've seen it done once in 10 years. Not common at all!

I try to get people to really think about what they can do under normal situations, vs. what they can do when it starts to hit the fan.
 
It depends on the stage pilot at UND...we have designated blocks of airspace that ATC will give us to use for maneuvers while still operating under IFR so that things like unusual attitudes, random holding, the like can get dune while operating under IFR. Our policy manual doesn't allow unusual attitudes or partial-panel flight while IMC, but nothing prohibits doing it while IFR.
 
http://rgl.faa.gov/REGULATORY_AND_GUIDANCE_LIBRARY/RGADVISORYCIRCULAR.NSF/0/8a2ae2491c85226f86256e35004c638b/$FILE/AC20-138A.pdf

Advisory Circular 20-138
Paragraph 18(d)(1)

(1) The horizontal (and vertical) deviation(s) display(s) and failure annunciation should be located within the pilot's primary field of view, as should any indication requiring immediate aircrew action. For the purpose of this AC, the primary field of view is within 15 degrees of the pilot’s primary line of sight.

The way the AC reads, you do not specifically have to have an external CDI (it specifically mentions things like "when an external CDI is used"), but for an IFR installation, the CDI (internal or external) has to be within 15 degrees of the pilots view.

And no, I did not know this off the top of my head, I just knew about where to look.
 
msmspilot said:
http://rgl.faa.gov/REGULATORY_AND_GUIDANCE_LIBRARY/RGADVISORYCIRCULAR.NSF/0/8a2ae2491c85226f86256e35004c638b/$FILE/AC20-138A.pdf

Advisory Circular 20-138
Paragraph 18(d)(1)

(1) The horizontal (and vertical) deviation(s) display(s) and failure annunciation should be located within the pilot's primary field of view, as should any indication requiring immediate aircrew action. For the purpose of this AC, the primary field of view is within 15 degrees of the pilot’s primary line of sight.

The way the AC reads, you do not specifically have to have an external CDI (it specifically mentions things like "when an external CDI is used"), but for an IFR installation, the CDI (internal or external) has to be within 15 degrees of the pilots view.

And no, I did not know this off the top of my head, I just knew about where to look.
Click to expand...

Oh sweet, I'll just put the 430W in my scan :) :laff:

I'd still be surprised if a field approval would be issued for an installation without an external CDI.

Interesting. Thanks!
 
Autothrust Blue said:
Oh sweet, I'll just put the 430W in my scan :) :laff:

I'd still be surprised if a field approval would be issued for an installation without an external CDI.

Interesting. Thanks!
Click to expand...

Hey, just reporting on what the FAA put out there. How it works in the real world? You probably need an external CDI with all the annunciators either in it or nearby. But then, that's speculation.

As a bit of advice for anyone about to install a GPS: Make sure the annunciators are tied into whatever dimming system you use for your panel lights. I flew a plane that didn't have that, and at night it would flat blind you.
 
msmspilot said:
Hey, just reporting on what the FAA put out there. How it works in the real world? You probably need an external CDI with all the annunciators either in it or nearby. But then, that's speculation.
Click to expand...
Yes...the letter, versus the spirit, of the law. Corollary, what is true in one FSDO is not necessarily true in another.

The sexiest presentations I've seen have all had some form of HSI - either your mechanical HSI, or some form of electronic HSI. King makes a nice EADI-EHSI and autopilot/flight director combination...now, I'm off thread.

As a bit of advice for anyone about to install a GPS: Make sure the annunciators are tied into whatever dimming system you use for your panel lights. I flew a plane that didn't have that, and at night it would flat blind you.
Click to expand...
We're about to do this in the BE50...having flown a few airplanes (King fitted) without this dimming, I wholeheartedly agree.

"Approach mode...ow, my eyes"
 
Is this one of those situations....

Imagine if people, only had the possibility to text but not make calls ever since the phone was invented...then in the last decade phoning people would become all the rage; "looky, I just pick up the phone, speed dial one and wham-o, I'm talking directly to the guy I called. I can actually hear his voice, I don't have to type and I get an instant response. Texting would be dead. Sexting would rage on though.

"Hey! The GPS has an internal CDI, great, get rid of the HSI."
10 years later...
"What if we married the GPS CDI to the DG."
"Brilliant"

I know that isn't really what this thread is about, but I have noticed that some of my students have a fatal attraction to the GPS screen.
 
Chief Captain said:
The G1000 thread below got me thinking...

On the G430/G530, is the moving map suitable for navigation?

I say no, the CDI must be used, because the map is just an aid to situational awareness; but I can't seem to find a concrete reference for that. Any help?

Also, let's say the panel mounted CDI fails, would the CDI on the first NAV page of the display be considered appropriate for course guidance?
Click to expand...

As long as you have some official navigation source displayed you are okay. For instance when navigating to an NDB, you should have an ADF tuned to the station. Whether your actually tracking the needle of following a picture on the GPS can be your own dirty little secret.

If you were to program the GPS direct to the NDB, the same applies. Who would know if you were paying more attention to the map than the external CDI?

As far as the legal concerns for the external CDI goes, when it fails in flight you do what you gotta do. I would report it to ATC but not let it deter me from shooting a GPS approach unless there were a better alternative for my equipment available. And of course follow the regs about getting it fixed before a later flight.
 
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