HansMatthijssen

GTN750 not picking up GS on RNAV/LPV approach (resolved)

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On 7/30/2018 at 4:44 PM, RXP said:

What about deactivating 'connect GPS to VOR indicator' ?

This seems to have done the trick. In a testflight right now and the aircraft ( Carenado Bonanza F33A) did pick up the glideslope perfectly!

Great help as ever, much appreciated!

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Thank you for your enduring patience!

Now the conclusion is interesting:

- when enabled, the GTN/GNS V2 override the NAV needles (using the X-Plane native dataref: "sim/operation/override/override_nav1_needles" - and "_nav2_" if GTN settings nav source is NAV2 ).

- it also override the "...nav#_hdef_dot", "...nav#_vdef_dot" and "...nav#_fromto"

- it does so in addition to the other independently controlled overrides (GPS, HSI).

Which makes me wonder if the issue is X-Plane failing to 'report' the needles/signal to other plugins when it is overriden (X-Plane bug) or if the issue is the 3rd party aircraft not picking up/handling the datarefs values, or lastly, if the GTN/GNS V2 is missing a few other datarefs to also override to make third party happy.

The later won't account why the third party aircraft is picking up things correctly when disabling 'override VOR' though. This leads me to suspect something in X-Plane or third party only?!?!

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And then the next test flight it didn not pick up the GS again.

I must be doing something wroing, forgetting something (if you do a "Load and Activate Approach" could it be that you need to Activate it once more from the Flight Plan page maybe?).
Anyway it worked the previous flight to the unit is fine (although it does still not swith off with the Master Avionics switch after landing, but thats no big deal). So I am going to repeat these flights and see what does/does not make it work.

No problem at all Jean-Luc, the Reality XP units are great addons, so if I can help figure out why this is happening it might help to make the product even better. I'll keep posting my findings.

Edited by HansMatthijssen

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Second and third test were also negative, the GTN750 did not pick up the glideslope.

After that I could only conclude that is most probably has something to do with the Simocders Reality Expansion Pack that I am using for the Carenado planes. So, I decided to load up the default Cessna 172SP and activate the GTN750 unit. I flew out, loaded and activated my approach (I keep flying the RNAV GPS RWY24 into Monauk, KTMP) and the GTN750 had no problems picking up the glideslope this time.

Preliminary conclusion seems to be that the GTN unit does not work correctly with the Simcoders REP. To test that further I am going to disable/uninstall the REP pack for the Carenado Bonanza F33A (my original aircraft that had problems) and try again.

I'll keep you posted.

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I edited my last post, but apparently that didn't come through.

So, I disabled the Simcoders Reality Expansion Pack (REP) for the Carenado Bonanza F33A and tried my same testflight again. Contrary to what I expected, the aircraft did not pick up the glideslope and remained in ALT HOLD mode. And again after landing when i turned off the master avionics switch, the GTN750 unit was not powered down.

So a summary:

  • Carenado Bonanza F33A with REP: GTN750 does not pick up the glideslope. GTN750 remains powered on after switching off master avionics
  • Carenado Bonanza F33A REP disabled: GTN750 does not pick up the glideslope. GTN750 remains powered on after switching off master avionics
  • Default Cessna 172SP: GTN750 picks up the glideslope without any problems.
  • All three aircafft: Using the X-Plane default GNS430 unit they all pick up the glideslope perfectly.

I have no idea what's going on, but it is getting a little bit frustrating by now.
I really do not want to be limited to default X-Plane aircraft using the GTN750. I bought it (same reason I bought the Carenados with the REPs) for added realism.

 

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Hans,

I also have the Carenado F33A working with the 750. I'm very much a novice at this but after reading your posts I figured it was time for me to try an approach with GS. 

My FP consisted of departure from KLGA ( I'm from Queens NY 🙂 ) RW22 with the first waypoint as KEWR and the next waypoint as KLGA with the approach RNAV 04 Y gps LPV and a vector of PONAE. After takeoff I climbed to 3000ft with A/P on NAV. After my plane made its turn to PONAE at KEWR I switched the A/P to APR and set in 1700ft with a descent rate of -900 ft/min prepping for arrival at PONAE.

At PONAE I engaged the VS and armed the ALT. I kept the airspeed around 140kts. I reached 1700ft prior to the next waypoint which is DNNIS. Within a second of reaching DNNIS the plane captured the GS and brought me down perfectly onto RW 04. Pretty neat function. So neat in fact that I turned the plane around at the end of 04, took off on 22 and successfully repeated it again.

I have the latest version of the plane itself, the GTN is 2.5.3.0 and the latest released STEAM version 11.25 I believe. Other plugins are XPUIPC for ATC and FlyWithLua for some scenery effects. I haven't yet bought the REP but may do so in the future.

My current settings for the panel display are posted here:

[GTN_750_1]
; comma separated list of read only settings.
locked = CopilotSide, RadiosPair, AutoNavSource, UseAudioPanel, FuelType
; comma separated list of render targets.
drawto = WINDOW, PANEL3D
; is the master device if true.
MasterDevice = true
; connects GPS to copilot side if true.
CopilotSide = false
; selects COM/NAV Radios '1' or '2'.
RadiosPair = 1
; uses computer time if true, simulator time otherwise.
ComputerTime = false
; reduce screen update rate by half.
ReduceRate = false
; integral lighting rheostat index (0 to 3) or percent (-100 to 0)
Rheostat.Display = 0
; integral lighting rheostat index (0 to 3) or percent (-100 to 0)
Rheostat.Buttons = 2
; connects GPS to HSI if true.
LinkHsi = true
; connects GPS to HSI course motor if true.
LinkCrs = true
; connects GPS to OBS input if true (LinkHsi/OBS or AutoNavSource/OBS).
LinkObs = true
; connects GPS to VOR if true.
LinkVor = true
; connects GPS to Autopilot if true.
LinkOto = true
; connects CDI key to NAV/GPS switch if true.
AutoNavGps = true
; enables automatic GPS/VLOC selection.
AutoSelect = true
; selects VLOC NAV '1' or '2'. '0' selects same source as 'RadiosPair'.
AutoNavSource = 0
; sets device power source: ALWAYS_ON,AVIONICS_BUS,MAIN_BATTERY
PowerSource = AVIONICS_BUS
; connects GPS to Shadin Air Data computer if true.
UseAirData = true
; connects GPS to Shadin Fuel Data computer if true.
UseFuelData = true
; connects GPS to Audio Panel if true.
UseAudioPanel = true
; connects GPS to Transponder if true.
UseTransponder = true
; connects GPS to RYAN 9900BX if true.
UseRyanTcad = false
; sets TCAD sound alerts volume in percent: 0 to 100.
RyanTcadVolume = 50
; enable device failures if true.
UseFailures = false
; uses Simulator GPS commands if true.
UseSimGpsCmds = false
; sets transponder VFR code (octal default: #1200).
VFRcode = #1200
; sets fuel type: AVGAS,JETA,JETB,DIESEL
FuelType = AVGAS
; sets ownship icon type: 
; AUTO,LOW_WING,HIGH_WING,KIT_PLANE,TURBOPROP,TWIN_ENGINE,SINGLE_JET,BUSINESS_JET,2BLADES,3BLADES,4BLADES,ARROW
OwnshipIcon = AUTO
; sets TAWS type: TERR,TAWS_B,TAWS_A
TawsMode = TERR
; sets TAWS surface: HARD,HARD_SOFT,WATER,ANY
TawsSurface = HARD_SOFT
; TAWS minimum runway length (feet)
TawsMinLength = 40
; TAWS approach air speed (knots), or -1 (auto detect Vref: 83)
TawsApprSpeed = 88
; TAWS maximum flap extension speed (knots) or -1 (auto detect Vfe: 154)
TawsFlapSpeed = 154
; TAWS maximum gear extension speed (knots) or -1 (auto detect Vle: 154)
TawsGearSpeed = 154
; sets voice type: MALE,FEMALE
VoicePref = MALE
; sets master sound volume in percent: 0 to 100.
MasterVolume = 100
; selects the default database: 0: 'Garmin (North America)', 1: 'Jeppesen (Worldwide)'
NavDbType = 1
; selects the CPU running the trainer process: 1 to 32
; 0: last core, -1: automatic.
CpuAffinity = -1
; sets TCAD maximum number of targets to X-Plane AI Traffic Count.
UseTcadAiCount = true
; updates Simulator GPS flight plan if true.
LinkSimGps = false
; saves the active route as a Simulator flight plan if true.
AutoSavePln = false
; mute sound when simulator window looses focus if false.
NoAudioFocus = false

Hope this helps you.

 

Daskal

 

 

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Hans,

Forgot to add that my 750 shuts off using the master avionics switch. I did notice that the plane's battery switch can be off and the 750 can still be turned on with the master avionics switch. I'm not sure if that's the case IRL though?

Daskal

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Hey Daskal,

Thanks for your reply. It is late here right now (the Netherlands here) but I will definitely check your settings versus mine.

The scenario you describe is exactly how it works for me if I use the default Cessna 172SP. I descend to the published glideslope intercept altitude using V/S, then the airplane stays at that altitude in ALT HOLD mode with APP mode selected and it will intercept the glideslope. Its also exactly how it works for my in any airplane if I use the default X-Plane GNS unit.

However for some reason it does not work in the Carenado F33 (with or without the REP). And I'm puzzled why that can be.

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Tried with your settings (which are basically the same settings I had but without VC integration).

It all does not make any difference. The GTN750 does not pick up the glideslope but remains in ALT HOLD mode.
It also does not power off when I swtich off the Master Avionics Settings.

I am going to give this one more go:
@Jean-Luc: Can you please point me to all relevant folders and registry settings, so I can uninstall the GTN unit, delete every folder and every registry setting associated with the unit and then do a complete re-install of the Reality XP GTN750.

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Hi Hans,

The issue you are experiencing couldn't be related to the installation itself, only to the 'communication' between the GTN plugin and X-Plane.

The first clue is the fact it does not power off. The code logic behind this is very simple: the plugin reads either 'battery' or 'avionics bus' datarefs, and power on/off the device accordingly. If this doesn't happen, it means the plugin is reading the wrong datarefs (improbable otherwise it would be widespread an issue), or something running in the context of your aircraft is preventing the dataref to update.

Let's focus on this one first then:

The two corresponding datarefs used (depending on your GTN power source setting) are:

"sim/cockpit/electrical/avionics_on"
"sim/cockpit/electrical/battery_on"

Can you cross check these change to 0 or 1 depending on your actions on the aircraft panel?

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Jean-Luc,

I have tested this again.

I use a .ini file from the forums here that does integrate the GTN70 in the virtual cockpit (but when I tried the one posted above in this thread there was no difference).

I start the plane cold and dark, both datarefs you mention have the value 0. Flipping the battery switch turns the sim/cockpit/electrical/battery_on value to 1. I then startup the engine, after which i flip the Master Avionics switch. That makes that the sim/cockpit/electrical/avionocs_on value is set to 1. The GTN starts up, the blank (black) screen comes to live and the unit starts to work (thats also how i have set-up the unit, so this is all correct).

After the flight I switch the Master Avionics off, the value for sim/cockpit/electrical/avionics_on changes to 0. I see a quick flicker in the GTN screen, but it does not go to blank. However it does seem to be "off" in that clicking on any of the buttons seems not to do anything anymore. I would expect the unit to really switch off though, meaning the screen would be blank.

After that i switch the battery off and that means the value for sim/cockpit/electrical/battery_on  is set to 0.

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Ok, so this seems normal (regarding datarefs). However, should the screen flickering and displaying the last visible screen image, instead of turning blank, there is something else not working correctly.

Can you please post the content of the RXP log files to cross check? (see User's Manual for file/path).

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Holidays over, so less time to experiment unfortunately.

The log files do not seem very interesting:

rxpGTN.xpl.log

18/08/14 17:27:52.808 08244 -    ] # win.xpl version 2.5.3.0
18/08/14 17:27:52.808 08244 INFO ]

rxpGtnSim.dll.log

18/08/14 17:27:56.519 08244 -    ] # rxpGtnSim64.dll version 2.5.3.0
18/08/14 17:27:56.518 08244 INFO ]
18/08/14 17:28:44.219 02668 INFO ]

 

Edited by HansMatthijssen

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Hi Hans and sorry for the delay.

Effectively the log files don't show anything meaningful. Nevertheless, lack of information isn't meaningless in itself!

What this most likely tells is that the GTN trainer seems closing fine (otherwise there would be log entries). Therefore, this shorten the probable cause list to a few candidates.

Can you please see if you are running near 100% RAM and video card resources when in the simulator? You can check the video card memory used directly in the X-Plane graphics settings (shown around the texture complexity slider). Otherwise, CTRL+SHIFT+ESC to open the task manager and check the 'memory' tab for any relevant information.

The 'stuck' screen roughly means there is something in the system preventing some 'final' communication between the trainer and the plugin (shut down notification) prior the trainer process closes. Our solution takes care to prevent the usual 'race conditions' when closing the process so I can only think of something 'delaying' the closing process somehow. This could be video card driver related, audio driver related, or usually anti-virus related.

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XPlane tells me right before switching off the Master Avionics: 1536MB of textures loaded (on a 4GB Radeon 290).

System tells me 4.4GB RAM in use (8GB installed).

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Hi Hans,

please allow us a few more days as we are working on the GTN Trainer v6.50 compatibility update.

Mind you, in this process we might have found a small potential bug in one of the code which runs right when the trainer shuts down, which may in effect get the trainer exit under some conditions. It seemed not triggered for the majority of our customers though, and this most likely is related to some other settings in Windows.

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I haven't changed anything, but I did switch planes flying with the Carenado Baron now. And no idea why but the GTN750 does pick up the glideslope suddenly.

Im gonna test the Bonanza later this week or in the weekend.

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Hi guys

I also have the same problem with capturing GS. Everthing else works fine.

I will check and try all the suggestions in this thread.

Im running X-plane 9.61, I dont think this is related to x-plane version at all. And XPR sell this as compatible with xp 9 as well!

After som test I will return with the results.

Note:  Why Im running XP 9.61? It is because of PFC hardware that does not have a plugin for newer X-plane version.  I spend a lot of money on PFC Cirrus II so I need to stay with XP9 (it is very stabile).

BR

Stefan

 

 

 

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14 minutes ago, StLu1000 said:

It is because of PFC hardware that does not have a plugin for newer X-plane version.

At least, we do ship the 64bits PFC DLL which handles the PFC_430 hardware.

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Hi Jean-Luc and others

I think I found something interesting today while testing many options due to RNP approach with GTN 750. Used different airplanes, different HSI, radar altitude, etc etc. No changes was the results that GS does not capturing by AP or flying by hand, however when I on the GTN push "visual" during approach procedure the AP and glide slope connects. This test was made on airport ESTA Angelholm, Sweden.

Im reading the GTN manual (many pages) to find out how it works and how it should be handled.

There is also when selecting approach a Approach ID to be filled in, I really dont know what that is and if it is needed if I got the approach and runway selected?

Im also use a real updated database. I have also manually edited the fix database with all fix that belongs to ESTA procedures, if that matters I dont know except that it is easier to follow the airplane on the map when flying the procedure route.  So if it doing something else I really dont know today?

Question:

How is RXP GTN calculating and get the glide slope information since there is no glide path transmitter at the airport?

Can we learn something from this?

BR

Stefan

Edited by StLu1000

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Stefan, 

18 hours ago, StLu1000 said:

How is RXP GTN calculating and get the glide slope information since there is no glide path transmitter at the airport?

I think that you have a deep misunderstanding of how RNAV (GNSS) works!

Firstly, may I offer you a copy of the PBN Manual, which I co-author, which takes you through, in what I hope are bite-sized chunks, what RNAV, RNP and GNSS (GPS) are all about.  It is quite an easy read, I hope, of quite a challenging subject.

As a direct response to your question, lateral and vertical navigation on the GTN works entirely on GNSS, which is space (satellite) based and has no ground element.

Thus the question of transmitters at the airport does not arise.  On a small pedantic point, but one which causes confusion, only ILS (which does have transmitters at the airport) has a glideslope.  If the vertical navigation is satellite derived, it is called a glidepath.

The GTN calculates the approach path, laterally and vertically, on a Visual Approach purely based on geometry.  It derives a line which is on the runway QDM, descends at 3° and crosses the threshold at 50' above the threshold elevation.  If terrain or obstacles make that path unsafe, the glidepath is removed and it only provides lateral guidance.

This calculation is not based on any published surveyed approach data.  It comes purely from an algorithm in the GTN software.

My suggestion is that you should improve your understanding of how RNP APCH works by skimming my book, and that might help you work out what is going wrong with your expectations and usage of the GTN and of RNP approaches.

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Hi Timothy

Very nice work with the manual. Thank you. 

I will read the manual to better understand how it really works and from that it will be more easy to trace strange behaiviour from RXP GTN 750 that could be normal?

I have tested RNP approach at Insbruck airport Austria it is follow calculated glide path but on ESTA Angelholm, Sweden it does not. Your manual will probally answer that question.

I heard today that ESTA is only approved as 2D approach. 

Its a learning curve to work thru to fully understand the system. Many issues in this forum is more a user understanding problem perhaps and I is one of them.

Thanks again for your attention in this matter

BR

Stefan

 

 

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Hi Folks,

I can't download the manual at the moment - but here is a brief summary on the RNAV approach types:

- LPV: Localizer performance with vertical guidance. Offers localizer accuracy and a WAAS-based glideslope, like an ILS. Also like an ILS, lateral sensitivity increases as the aircraft approaches the runway. Minimums are published as a decision altitude (DA).

- LNAV/VNAV: Lateral/vertical navigation. Unlike an LPV procedure, lateral sensitivity does not increase as the aircraft nears the runway. Glideslope information is based on WAAS or barometric altitude. Minimums are published as a DA.

- LNAV: Lateral navigation. Similar to an LNAV/VNAV procedure except no glideslope is presented. Sensitivity does not increase as one nears the runway. Minimums are a minimum descent altitude (MDA), as with a VOR or localizer-only procedure.

- LP: Localizer performance. No vertical guidance provided. Sensitivity increases as the aircraft nears the runway, as with a traditional localizer. Minimums are an MDA.

- Stand-Alone GPS: The old-style GPS approach is basically an LNAV procedure but restricted to using only GPS. Offers an MDA.

Regards,

Scott

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@scottb613

I am sorry to have to correct some of that.

LPV - spot on

LNAV/VNAV - not quite right.  If you are using a TSO-146() receiver, such as the GTN or GNSx30W, both the lateral and vertical elements are angular.  If you have a TSO-129() receiver, such as the GNS430 (without the W) then you could fly it as an LNAV approach, with linear FSD, but only if you have Baro-VNAV.  This is a GTN forum, so all LNAV/VNAV we discuss will be angular.

LNAV - again, close, but no banana.  If you fly an LNAV approach on a GTN, or any other TSO-146() receiver, it will present angular lateral guidance.  Only on TSO-129() boxes is it linear.

LP - Yes.  The main difference between LP and LNAV is that the spec is different.  You cannot fly an LP approach on a TSO-129() receiver, so it will always be angular.

From a technical point of view, LP and LPV are differentiated from LNAV because they have a FAS Data Block which defines the Final Approach Segment.

You have missed two other approaches from your description:

LNAV+V - This is an LNAV approach, but Garmin have provided an unofficial, unapproved glidepath, which is a straight line from the FAF to the MAP.  You still have to use check altitudes and the LNAV MDA, but you are given guidance to help you stay on the correct slope.

Visual Approach - calculates the approach path, laterally and vertically, on a Visual Approach purely based on geometry.  It derives a line which is on the runway QDM, descends at 3° and crosses the threshold at 50' above the threshold elevation.  If terrain or obstacles make that path unsafe, the glidepath is removed and it only provides lateral guidance. This calculation is not based on any published surveyed approach data.  It comes purely from an algorithm in the GTN software.  It is not approved for use in IMC.

Stand-Alone GPS - I think a misunderstanding.  The other approaches above differ on the Final Segment (ie the differences are only really relevant between the Final Approach Fix through the Missed Approach Point to the end of the first segment of the missed approach.)  The Stand-Alone GPS approach is an old-fashioned way of describing the earlier parts of the procedure, ie from the Initial Approach fix(es) through the Intermediate Fix to the Final Approach Fix and all RNP/RNAV approaches have an RNAV 1 portion before the IF.  So the expression Stand-Alone GPS is no longer in use.

A couple of final points. 

Approaches are not LPV or LNAV/VNAV or LNAV.  One RNAV (RNP) approach can be all three.  It depends on the surveys that have been performed, the equipment available on the flightdeck and the integrity of the Signal-in-Space at the time and place.

The naming of approaches.  Over the years they have been called GPS, GNSS, RNAV (GNSS) and RNP.  The ICAO standard is that they must all be called RNP by 2022, but the USA has filed a difference and in the States they will continue to be called RNAV, with RNP reserved for Special Authorization Required approaches.  Most of the receiver manufacturers (such as Garmin) are American, so they intend to retain the RNAV nomenclature even when the rest of the world goes to RNP.  (Sorry, Jean-Luc, I don't know where Canada stands.)  This is going to cause infinite confusion.  A friend of mine nearly had his jet impounded by the Egyptian authorities over this ridiculous mess.

I am sorry that you have had difficulty downloading the Manual, but when you do, all this will be clear.

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It occurs to me that there is another kind of approach available in the latest software (v6.50).   

You can set any user waypoint to be an airport.  You can then fly DCT to that waypoint and use VNAV to create a glidepath of any angle you choose.

In this case, both lateral and vertical guidance will be linear, so it will be pretty inaccurate, but, if you make your minima high enough it should work.  It is worth setting the CDI scale to 0.30 nm to improve the lateral accuracy.  Guidance will then be the same as an LNAV/Baro-VNAV approach on a TSO-129() receiver. 

This has the advantage that you can set up an approach to your own strip, or any PinS for helicopter pilots, but is inaccurate and doesn't have the integrity safeguards of a published approach.

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