It doesn't take Einstein to recognize that this is pure nonsense,

 

LOL Yeah, that wasn't my brightest moment. I think I mixed up a few things which I read here and there. I better stop 'helping' on this subject. ^_^

I better stop 'helping' on this subject. ^_^

But you were a big help when you said that this AP coupling was possible with FSX/RXP430. I easily found old threads from 2009 where people were complaining that this was not working but then came this big announcement in 2010 in which Jean-Luc claimed that now WAAS approaches in his product could be fully AP-coupled. It only shows you how out-of-date is my FSX info, I admit haven't fired it in a very long time.

Well, perhaps some good has come of my butting in here. Again, sorry about potentially hijacking the topic.

 

Ahhaa! As a result of a web search I found this youtube clip.

 

 

Watching it, I recalled I have this full video and forgot about it. It is real world, not FSX, so doesn't speak to autopilot coupling. It certainly explains the RNAV LPV approach. Still not sure about autopilot coupling. I was flying approach in a Carenado King Air C90T and the vertical coupling did not seem to work. I am reasonably sure that the coupling does work with the 430 and the autopilot in the Carenado A36 Bonanza. I may get time this evening to fly a couple of more approaches in each aircraft.

Okay. Here's the followup scoop. The autopilot (in my case the autopilot in both the Carenado Bonanza A36 and the King Air C90T) will/does couple to the GPS for vertical guidance or coupled approaches to an RNAV approach as long as the RNAV approach includes either APV or LNAV/V or LNAV/LVAV. I flew several successful coupled approaches tonight into both KTPA (Tampa, FL) RNAV 01L, and KBMG (Bloomington, IN) RNAV 17.

 

I flew approaches in both the A36 and in the C90T. Both of these approaches are RNAV LPV. I was on autopilot with altitude hold at the time I activated the approaches, and did not hit the APR button on the autopilot until intersecting the final approach course and the indicator on the RXP430 GPS changed to "APV". Then, unlike the other day, I kept my hands off the AP ALT switch.

 

I think what had previously confused me was the way the AP and GPS control the ALT function of the AP. The published approach plate for KBMG RNAV 17 shows descent from 3000 starting at ITYEF, some 11.5 miles out, reaching 2500 at the FAF, which is OGUSY. The GPS and AP did not start the coupled descent from 3000 until near OGUSY, which is only 5 miles out. By that time the PAPI has been white from side to side for 2 minutes or more. The other day that confused me, making be believe that no vertical guidance was being provided. I'm sure I got anxious and deactivated the ALT function manually and took over the descent myself. Tonight I was more patient and waited it out. The GPS did in due course extinguish the AP ALT function and took over. It managed a steeper descent, but it got the dot on the mark and kept it there to the tdz. The key to a successful approach is to verify LPV on the GPS enunciator, activate the APR button on the autopilot, and then keep hands off the ALT button! (and be patient)

 

One last thing that added to the mix was my attempts to fly an RNAV LPV approach into KESN (Easton, MD) via RNAV 22. It is published showing LPV. I flew three approaches to RNAV 22 tonight and could only get the LNAV on the CDI enunciator on the RXP430 GPS. LPV was never indicated. Duh! I am using the current approach plate, but my Garmin database is dated May 11, 2011. It dawns on me that LPV approahes are being added all the time and that obviously some LPV approaches have been added since May 2011. I think that's what's going on with KESN.

Well, perhaps some good has come of my butting in here.

 

Sure has! That were two interesting posts! Pity they are buried deep in the 737NGX forum though... ^_^

 

Yes, RNAV approaches are being added everywhere all the time while we type: it's a pity we can't keep our virtual GNS's up to date... It's also a pity that there is no easy way (that I know of) to find out which airports in FSX have an LPV approach in the RXP GNS database... It's already pretty hard finding out which airport has an RNAV approach, let alone what type. I never know what kind of approach I am going to get until it is already activated.

AHH! A quick Google and here in the results is a link to a page containing an Excel file with a list of dates for US APV approaches, accompanied by the initial publication date (rightmost column). The spreadsheet is configured with filters, so you can use the dropboxes to control sorting:

 

http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/approaches/index.cfm

 

Interesting that the RNAV 22 approach to Easton is listed in this LPV spreadsheet and has an initial publication date of 05 JUN 08, which is three years before the Garmin update I am using with my RXP GPS's. You would think any of these before 11 MAY 2011 would be included in the current Garmin trainer database.

I have posted a new topic to follow up on the issues I was dealing with at:

 

http://forum.avsim.net/topic/393215-flying-coupled-rnav-approaches-with-vertical-guidance/

You would think any of these before 11 MAY 2011 would be included in the current Garmin trainer database.

I flew three approaches to RNAV 22 tonight and could only get the LNAV on the CDI enunciator on the RXP430 GPS.

Don't you have capability to check all approaches available for a given airport in RXP430?? You should know exactly what is available in the airport's database without having to wait for CDI anunciator. But of course don't expect that in the trainer everything will be 100% reliable, I recall distinctly when using my G1000 trainer that an airport could show that LPV was available but in fact it wasn't, be prepared for such apparent, infrequent paradoxes.

Don't you have capability to check all approaches available for a given airport in RXP430?? You should know exactly what is available in the airport's database without having to wait for CDI anunciator. But of course don't expect that in the trainer everything will be 100% reliable, I recall distinctly when using my G1000 trainer that an airport could show that LPV was available but in fact it wasn't, be prepared for such apparent, infrequent paradoxes.

 

You can see the available RNAV approaches, and respective IAF's, but it does not provide information on whether the approach is LNAV, APV, or VNAV. You don't see that until the annunciator advises you when you are on the final approach course.

but you cannot tell that you will find LPV or VNAV vertical guidence with the approach until

Then we have seen similar problems but in my G1000 trainer (independent of FSX) it is quite rare to have say an LPV approach and not get vertical guidance. The trainers do not simulate real world WAAS downgrades so if everything was working at 100%, per design you should never have to guess whether you get vertical guidance or not.

But if you watch the video above in this thread you will understand that even if LPV capability is there it might not be functioning at any point in time. So you can see the capability on the approach plate, but you will not know for sure that you will receive the vertical guidence until the annunciator displays the indication. Though it certainly lists the RNAV approaches in the database I don't know of any way the RXP 430 (or Garmin GNS430 for that matter) displays the specifics of APV vs VNAV vs LNAV for any given RNAV approach.

 

Whoops! I stand corrected. I just poked around in the Select Approach function and I see that once an RNAV approach is selected and the transition selected the 430 does display the RNAV type in the lower right corner. I've flown RNAV LPV approaches into four different airports today and never noticed that as i cycle though the approach selection. Guess I have been making the selection too quickly to see that. Thanks! I learned something else good today!

 

Edited December 6, 201213 yr by fppilot

But if you watch the video above in this thread you will understand that even if LPV capability is there it might not be functioning at any point in time.

But this is precisely the point I was making above - in real life LPV may not be 100% guaranteed due to WAAS downgrades but your trainer doesn't simulate stuff like that so you should have your LPV (with vert. guidance) guaranteed provided it is in the menu and you loaded the approach.

 

 

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