GNS430 and Felis Tu-154

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Hi there, 

at first I am sorry for new topic, but I am little bit frustrated from this situation. I've tried almost everything to use the RXP GNS 430 in Felis Tu-154, but I still can't find the "right magic combination". Is there anyone who successfully uses this combination? So Tu-154 and RXP GNS430. When I want to follow GPS, the airplane turns completely off the track. CDI is still bumping, but the biggest problem is that plane don't follow GPS track, althrough in version 2.0.1. it should be possible to use third party plugins for navigation. 

At Felis part of forum they answer me, what must be set in Tupolev, but when I set it it's still doesn't work together. Plane may use default XPL parameters. Citation from Felis:


"If you want more info for those guys, here the DataRefs, that use for ABSU:

sim/cockpit/radios/gps_course_degtm -- magnetic course
sim/cockpit/radios/gps_hdef_dot -- course deviation
sim/cockpit/radios/gps_hdef_dot -- from-to flag"

Can somebody help me pls? 

I want use this DIY with this nice "bird". 


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This may be too simplistic of an answer, but did you set the settings to connect to the Autopilot?

Give us more details of your settings.


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Here is GNS Config. In Tu-154: GNS430 on GND panel is selected, NVU-GPS switch to GPS and of course on ABSU is NVU power set.

; comma separated list of gauges
gauges = GNS_430_1

; comma separated list of render targets.
; 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
; integral lighting rheostat index (0 to 3) or percent (-100 to 0)
Rheostat.Display = -100
; integral lighting rheostat index (0 to 3) or percent (-100 to 0)
Rheostat.Buttons = -75
; connects GPS to Autopilot if true.
LinkOto = true 
; 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 = false
; connects CDI key to NAV/GPS switch if true.
AutoNavGps = 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
; sets device power knob switch mode: NONE,DEFAULT_ON,DEFAULT_OFF
PowerKnob = NONE
; 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 RYAN 9900BX if true.
UseRyanTcad = true 
; sets TCAD sound alerts volume in percent: 0 to 100.
RyanTcadVolume = 50
; sets TCAD maximum number of targets to X-Plane AI Traffic Count.
UseTcadAiCount = true 
; connects GPS #1 to GPS #2 if true (both required).
UseCrossFill = false
; enable device failures if true.
UseFailures = false
; uses Simulator GPS commands if true.
UseSimGpsCmds = false
; sets fuel type: AVGAS,JETA,JETB
FuelType = AVGAS
; sets TAWS type: TERR,TAWS
TawsMode = TERR
TawsSurface = HARD_SOFT
; TAWS minimum runway length (feet)
TawsMinLength = 40
; sets master sound volume in percent: 0 to 100.
MasterVolume = 100
; mute sound when simulator window looses focus if false.
NoAudioFocus = false
; selects the CPU running the trainer process: 1 to 32
; 0: last core, -1: automatic.
CpuAffinity = -1
; connects to: 'PFC_STACK','PFC_430','PFC_530' or any '#PID' (#D002 for PFC_430)
; no value connects to first found, 'OFF' disables connection.
HardwareDevice = 
; hardware selector number or -1 to disable.
HardwareIdx = -1


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Posted (edited)

GNS v2.4.1 Still doesn't work with Felis Tu-154. 😭

Edited by RXP

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@Hamel I'm sorry it took time to answer, v2.4.1 was in preparation with a fix that might have been solving the issue with the TU154 as well. It seems not with this aircraft though.

One thing you can do: open dataref editor, and monitor the dararefs you've mentioned above as your program/change route on the GNS and see if they also change accordingly. If they don't, something in the TU154 is preventing third party GPS to override these variables. If they do, something in the TU154 is not taking these datarefs in account then.

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At first, thanks for reply and sorry if I wrote to wrong topic. 

I am relativly new in XPL, so sorry if I write something wrong. 

I test this:

  1. open Tu-154
  2. Open dataRef monitor and find line sim/cockpit/radios/gps_course_degtm
  3. Open default GNS 430 and RXP GNS430
  4. Change DCT to one point in default GNS. Vallue correctly changed to 54
  5. change DCT to other point in RXP GNS 430. Vallue doesn't change. 
  6. Test this metod on few other points

I don't know if this is right procedure and if this will help. 

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Thank you, this is exactly what to look for!

With the GNS set as 'Master Device', the only explanation for the "sim/cockpit/radios/gps_course_degtm" dataref not changing is that the aircraft plugin/lua/whatever code, or another loaded plugin, is forcing the "sim/operation/override/override_gps" dataref to 0.

This was the issue behind the need for unselecting then reselecting the GNS prior v2.4.1 in some aircraft like Carenado for example. Since v2.4.1 the GNS V2 plugin is monitoring this 'override' dataref and changes it back to 1 if not set.

Normal 'override' operation requires 'Master Device' enabled, and the GNS in GPS mode.

Can you please then cross check what is the value of the 'override_gps' value in dararef editor and how it changes?

Also, can you please clarify the acronyms you are using (ABSU? NVU? DCT?) otherwise it might makes things a lot harder to understand.


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I find sim/operation/override/override_gps and this vallue is still jumping between 1 and 0. 

ABSU is Autopilot in Tu-154, NVU is type of navigation and DCT is Direct to button on GNS unit. 

I am not good in english so sorry for my English. I hope its everythink you was request from me 🙂 

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Posted (edited)

Perfect: the issue lies in the TU-154. Here is the explanation:

- Their A/P system 'enforces' setting override_gps to 0 if they are not in control, or to 1 if they are.

- Our GNS 'enforces' setting override_gps to 1 if it is supposed to, otherwise it doesn't change it.


In turn, they must change their code like this:

1) when the A/P system stays 'in control' (say when you want their A/P system to fly the aircraft), they must in their 'frame'/'update' loop:

    a) read override_gps value

    b) set it to 1 if it is 0 and wait next frame

    c) otherwise if it was 1 then they can proceed as normal.

2) when the A/P system changes from 'in control' to 'not in control' (say when you want a third party GPS to fly the aircraft), they must just write ONCE ONLY override_gps with the value 0.


Edited by RXP

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Thank you very much for your help and for your support. I will try write it to Felis 🙂 

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I've edited my post to make some points clearer.

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