Fond du Lac DME arc FAF question

[nddons]

I flew the LOC/DME RWY 36 approach this afternoon http://204.108.4.16/d-tpp/1003/05231LD36.PDF and had an interesting discovery.

I fly a 172R with a King GPS, which I used for my DME information. That presented no problem, UNTIL I attempted to define the FAF. Unlike the VOR/DME RWY 36 approach, which uses the OSH VOR to define the 26 DME arc as well as the FAF, this approach defines the FAF as DME from the localizer antenna. My GPS does not have that point as a fix, so if this was a real approach in IMC, I do not believe I would have been legal to fly this approach, because I could not define the FAF by the navaid.

I used the airport as the navaid just to fly this practice approach in VMC, but learned about the limitations of GPS. In IMC I could have flown the VOR/DME approach to get in to the airport, but didn't realize the limitations of the GPS that I was using. (And yes, the database was current.)

So my question is, would more advanced GPS systems have this fix in the database, or is this a case where you actually must have DME (and not a GPS substitute for DME) to fly the approach?

 

[Areeda]

I haven't used a King GPS in a while but I checked this approach in the Garmin 430W simulator.

My first question is is the approach in your database? If not you cannot fly it with that GPS.

If it is in the database, it should have all the waypoints needed. In the garmin these are labeled:
ERAGE(IA), dme arc, D165Z, GODEC, CADVU(FA), RW36(MA), OSH (MH), hold

Joe

 

[TMetzinger]

FAF on this fix is defined as a named waypoint - CADVU, so you can use the GPS for that point, and the MAP is defined as a named waypoint as well.

So I believe you can use the LOC for lateral navigation and the GPS for DME using those waypoints.

 

[Areeda]

I was wrong about an approach like this having to be in the database. I posted too late at night without enough thinking.

As Tim said if the waypoints are in the DB or the DME/Navaid you can use the GPS to identify waypoints.

But if the DME/Navaid and the waypoints are not there I don't think you can.

Joe

 

[John Collins]

FAF on this fix is defined as a named waypoint - CADVU, so you can use the GPS for that point, and the MAP is defined as a named waypoint as well.

So I believe you can use the LOC for lateral navigation and the GPS for DME using those waypoints.

I agree with Tim. The only question you have to resolve is are CADVU and BIBME in your King GPS database. If they are, then there is no problem.

 

[poadeleted20]

My first question is is the approach in your database? If not you cannot fly it with that GPS.

Since this is a LOC/DME approach without "GPS" in the title, he can't fly it with his GPS, period. All he can use his GPS for is situational awareness and a DME substitute, and for the DME part, he doesn't need the approach in the database -- just a point he can reference for the DME work. As noted by others, if he has either CADVU or BIBME in the database, he's good to go on the DME side with either the FAF being 3.9 from BIBME or the MAP being 3.9 from CADVU.

 

[gismo]

Since this is a LOC/DME approach without "GPS" in the title, he can't fly it with his GPS, period. All he can use his GPS for is situational awareness and a DME substitute, and for the DME part, he doesn't need the approach in the database -- just a point he can reference for the DME work. As noted by others, if he has either CADVU or BIBME in the database, he's good to go on the DME side with either the FAF being 3.9 from BIBME or the MAP being 3.9 from CADVU.

He can't fly the final segment with GPS but AFaIK it is legal (and desirable) to fly the arc leading to the final segment using GPS guidance including GPSS and/or the CDI indications along the arc provided by many IFR GPS boxes.

 

[nddons]

Since this is a LOC/DME approach without "GPS" in the title, he can't fly it with his GPS, period. All he can use his GPS for is situational awareness and a DME substitute, and for the DME part, he doesn't need the approach in the database -- just a point he can reference for the DME work. As noted by others, if he has either CADVU or BIBME in the database, he's good to go on the DME side with either the FAF being 3.9 from BIBME or the MAP being 3.9 from CADVU.

You're right, Ron. I was getting hung up on the DME aspect, when I just could have put in the darn 5-letter identifier for CADVU or BIBME into the GPS and counted down for the FAF and counted up for the MAP.

I was doing this partial panel (AI was really INOP) and my CFII turned the #1 COM and NAV radios off, so my HSI became simply a DG, and I used the #2 CDI for both the arc and the LOC. I also had about a 14 kt tailwind on the approach, so things were moving pretty fast for me. No excuses, though. I should have thought all that through on the ground, not when I was working through my WIRE checklist.

 

[poadeleted20]

He can't fly the final segment with GPS but AFaIK it is legal (and desirable) to fly the arc leading to the final segment using GPS guidance including GPSS and/or the CDI indications along the arc provided by many IFR GPS boxes.

Correctamundo.

 

[poadeleted20]

You're right, Ron. I was getting hung up on the DME aspect, when I just could have put in the darn 5-letter identifier for CADVU or BIBME into the GPS and counted down for the FAF and counted up for the MAP.

Ayup.

I was doing this partial panel (AI was really INOP) and my CFII turned the #1 COM and NAV radios off, so my HSI became simply a DG, and I used the #2 CDI for both the arc and the LOC. I also had about a 14 kt tailwind on the approach, so things were moving pretty fast for me. No excuses, though. I should have thought all that through on the ground, not when I was working through my WIRE checklist.

Good for your instructor, because now is the time to be learning how to do this, not on the practical test. OTOH, bad for your instructor for not having taught you how to deal with this issue on the ground first, not in the air. Teach on the ground, practice in the air.

 

[hindsight2020]

Good thoughts all around.

My only thing about this discussion is....I don't know, it all seems like a false economy to me. Had you had DME on-board you wouldn't have had this whole "problem". I think it's pretty realistic of an outcome for the average occassional user of GPS buttonology in real-world conditions. Had you had to shoot this approach in anger as a plan B, your SA would have been just as diminished as in that scenario; GPS would have not been your friend that day. Granted you would have probably shot the LOC no problem using the first thing you could haphazardly plug into the GPS for distance, but all hassle would have been negated by a) being a super hero at GPS button-on-the-fly or b) having that clunky DME in lieu of panel mounted GPS. Go figure. Good training though, that's high value stuff that will stick with ya k:

I'm an IFR minimalist at heart. What's a DME 890+installation? 2 grand? Plus a Garmin 196 (which you can back up the actual approach no less)? And no database upkeep? That's a cleaner result AND the GPS portion of your "suite" is battery backed-up versus the thirsty panel mount. What's an IFR GPS installation these days? 5-6-10 grand + 300/yr ? For all that button pushing away from your scan in the nasty grey? Yikes....

 

[poadeleted20]

My only thing about this discussion is....I don't know, it all seems like a false economy to me. Had you had DME on-board you wouldn't have had this whole "problem". I think it's pretty realistic of an outcome for the average occassional user of GPS buttonology in real-world conditions. Had you had to shoot this approach in anger as a plan B, your SA would have been just as diminished as in that scenario; GPS would have not been your friend that day.

The solution to that, I think, is not to dismiss GPS's, but to get the proper training for it on the ground before you try to use it in the air.

Granted you would have probably shot the LOC no problem using the first thing you could haphazardly plug into the GPS for distance, but all hassle would have been negated by a) being a super hero at GPS button-on-the-fly or b) having that clunky DME in lieu of panel mounted GPS. Go figure.

Given the myriad uses of an IFR approach GPS versus the comparatively limited uses of a DME, I don't think that's an appropriate comparison.

I'm an IFR minimalist at heart. What's a DME 890+installation? 2 grand? Plus a Garmin 196 (which you can back up the actual approach no less)? And no database upkeep? That's a cleaner result AND the GPS portion of your "suite" is battery backed-up versus the thirsty panel mount. What's an IFR GPS installation these days? 5-6-10 grand + 300/yr ? For all that button pushing away from your scan in the nasty grey? Yikes....

Yet, that IFR GPS will provide capabilities which can make it possible to get where you want to go when VOR/DME won't. After 15 years of flying with IFR GPS's, I'm convinced I made the right decision installing one in each of the three planes in which I have done that.

 

[gismo]

I'm an IFR minimalist at heart. What's a DME 890+installation? 2 grand? Plus a Garmin 196 (which you can back up the actual approach no less)? And no database upkeep? That's a cleaner result AND the GPS portion of your "suite" is battery backed-up versus the thirsty panel mount. What's an IFR GPS installation these days? 5-6-10 grand + 300/yr ? For all that button pushing away from your scan in the nasty grey? Yikes....

Well FWIW I have a good IFR GPS (GNS480) and a decent DME (KN64) in my panel and due to the highly effective nature of the GPS I rarely turn the DME on. Sure GPS is more "complicate" but that's primarily because it offers so much more.

That all might be fine for an "IFR minimalist" (does that mean a single navcom plus DME?, I'd think that DME would be "excessive" for a "minimalist), but having flown "hard IFR" with minimal avionics, I really appreciate the capabilities offered by IFR GPSMAP devices and would hate to go back. And if you haven't tried that (including the necessary familiarization training) I wouldn't be so fast to knock it.

And JOOC, what makes you think a 196 with a three year old DB would be a good back up on any approach?

 

[John Collins]

I am sure that there must be G1000 systems with a DME installed as provisions are made for a DME, but I have yet to come across one.