RNAV Approaches Not Working

That only works for ILS. You don’t switch modes for RNAV. You keep it in GPS mode.

Most reasons RNAV doesn’t work is not hitting the Final Approach Fix (FAF) at the required altitude per the Approach Chart. If you’re over the alt fix, you’ll just watch that magenta diamond slide toward the bottom of the range with nary a glideslope.

Additionally, because VNAV isn’t implemented in some of the Garmins, you must maintain a 3 degree glideslope descent even after you passed the FAF at the correct altitude fix.

Theoretically, passing the FAF at the alt fix should trigger the GS/GP capture (from White to Green in the Annunciator panel) and AP starts descending using the signal.

Practically speaking, it might be another .5 nm or so past the FAF before GS/GP kicks in. For approaches where the runway shares both an ILS and an RNAV approach, there is strong correlation between passing over the ILS Outer Marker (you can hear the custom beep) and the RNAV GP/GS activating. I’ve experimented where I have the ILS frequency dialed into NAV1 so that if RNAV doesn’t kick in for whatever reason, I can switch to NAV1 to pick up the ILS and pitch down as needed to get under the glideslope cone.

1 Like

Could you share what type of aircraft you are using? And what, if any, mods you have installed (only those mods relevant to your question).

And even better … any screenshots on how you execute your approach?

BTW. Just tried earlier EDDF 25C RNP Z with the FBW stable (via CHA and FAF REDGO at 4000ft, 707ft minimums). Although I initially thought it would not, the GS was captured fine (APP NAV appears in PFD) and without ILS (ie ILS frequency empty in the RAD NAV MCDU page). Instead of the diamond a magenta square appears the PFD. So I stand corrected to my initial statement above, at least for this mod.

(post deleted by author)

2 Likes

Thx. Very nicely summarized.

So that’s why the above mentioned EDDF 25C worked as it does not have any WP between FAF and MAP. … I wonder what LOWI from the West would be like?

I agree with this. I have found the ILS NAV1 approach both accurate and more fun to fly.

I have never had any RNAV issues with TBM and WT-3000, I also use Navigraph data.

That’s the intent of G1000 NXi is to finally add new Procedure Legs including MA. All the work they did in the CJ4 is now inside the NXi plus new stuff.

Not all RNAV approaches have glideslopes (in the RW or sim). In FS, I’ve found that most RNAV approaches that are supposed to have them do (not all), and some that are not supposed to have them occasionally have them. :slightly_smiling_face: I don’t know if the installation by the encoders of GS for RNAV is done through the airport or runway or coded separately - regardless there are some errors for some approaches.

As some have noted, the WT g1000 and g3000 mods will capture and follow some of these RNAV glideslopes - though they are not functioning exactly as they should as compared to the RW, they are functioning and will give you some coupled guidance. Also, the recommendations to be at the proper FAF altitude and to begin a standard 3-degree descent is appropriate. I would also recommend that you switch the AP over to APR mode prior to that descent point.

Finally, I also highly recommend the pms50-GTN750 nav mods! They also do a great job of capturing existing glideslopes at some airports. I have used this mod in place of the g1000 in the C172, G36 and c208b.

RNAV approaches have been working fine for me for quite a few months flying the TBM 900 without any mods. I do use the Navigraph data… might have something to do with it.

I have rediscovered RNAV since a lot of smaller airports that don’t have ILS have it. It makes it nice using NaviGraph to set up an approach for an airport you are unfamiliar with.

I although I get repeatable GP locks I sometimes have to “feel around” for them by starting the descent to the runway while the RNAV gets itself together. I hit the FAF at the proper altitude per the chart, the GP doesn’t synch as consistently as the ILS GS does. As noted, the red diamond seems to want to sit at the bottom of the ribbon, come up close to the lock point, float around for a bit, and finally when you’ve resigned yourself to using pilot skills to land, will lock-in.

It probably needs some fine-tuning somewhere in the SW (IMHO)

That’s been a visual bug with RNAV since launch. To the best of my understanding, that diamond should behave the same as it does for ILS, but it doesn’t. Hopefully the WT G1000NXi and G3000 will finally address this once the new nav system is in the sim as of the 27th.

UUBL airport beacon, default cessna 172 (with gauges)

UUBL doesn’t have an RNAV procedure according to the NavData.

It has a co-located DME, but that won’t provide you with vertical guidance to termination.

Do you mean UUBI? Because that’s the nearest airport to UUBL with any vertical guidance - it has a Yankee and Zulu rated ILS.

Otherwise you’d have to head to Moscow or Nizhny Novogrod, or maybe Yaroslavl.

2 Likes

(post deleted by author)

1 Like

That DME didn’t work (for me?), yes. Its listed in databases, but does not affect direction finders and radio equipment in any way, as if it does not exist at all :confused:

yes it is. My point was if you have done a great flight and you see the glideslope dropping but the GPS system doesnt pick it up then you can be annoyed and ditch the flight or, having programmed CRS and nav1 with localiser beforehand just in case, switch and perform a landing. That would be more satisfying than just ditching the landing. But it isnt a fix.

I’m still about 50/50 on these RNAV approaches. Maybe I’m doing something wrong. Shot one yesterday into Brownwood, Texas, it didn’t work, never caught the GS. Shot one today into Georgetown, Texas, same thing. If it doesn’t have an ILS approach I’m in trouble.

(post deleted by author)

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.