Aircraft initiates 180 deg turn when cdi btn for gps to vloc

[Bill_S 0]

I have loaded an ILS approach onto the reality xp 530W/430W pair and the aircraft follows the Approach plate onto the designated IA and then onto the ILS approach course via gps nav turn.    The SW switches from term to LNAV correctly.    Then as the cross over point Arrives and msg pops to switch cdi off gps to vloc the aircraft does a 180 turn to fly away from airport and the loc when pushed.    This is consistent turning away behavior with maybe 4 or 5 tries and re-checks of approach configurations loaded correctly.

 

I have tried the front course and back course directions on the cdi as well as verified the nav loc ident is showing properly on the gns530 for the airport.

 

Any help you can give on why it keeps wanting to turn the a/c away from the airport on outbound radial vs landing approach and proper HSI / CDI needles would be great.

 

Aircraft = stock C172 with Garmin 530/430 pair.  Using RXP overlay SW, V2.

 

attempted lnav and leg sequencing for active intermediate to FAF point AND after FAF sequences with warning to switch to vloc from gps mode. No joy following approach as cdi push still causes 180 deg turn.   IAF = EMI with Numby course turn onto ILS course for KFDK.  No precision turnabout required from EMI.

 

thanks,

Bill

[Bert Pieke 7,584]

Not entirely sure at what point this occurs.. but the "proper" sequence is to set the heading bug to the runway heading and after the turn to final to first switch the autopilot to heading mode.  Then switch the GPS to VLOC mode and check the HSI needles.. only if that all looks good, switch the autopilot to APR mode.

Try that and see if it all goes to plan..

[Bill_S 0]

Will do, thank you.   My weekend awaits.

[RXP 2,338]

Hi,

Thank you for continuing on the forum where it is most helpful to the majority.

I'm copying/pasting below some of the relevant information from our private discussion which might further help finding a solution to this, thanks to others input too.

 

Quote

 

Bill_S:

Only when I push CDI to switch from gps to nav mode for vertical HSI nav does it turn 180 facing away.  I have checked if it’s trying a procedural turn around and it never comes back towards the airport.

The loc is loaded into the nav comms with positive ID on Morse and ID on the Garmin.   

Thank you for replying.  P.S., love the SW.

 

 

Quote

 

RXP:

Nevertheless, when in VLOC mode, the GTN/GNS V2 is not interacting with the autopilot at all.

Are you using the Cessna 172 with G1000? In this case the issue is the X-Plane G1000 which won't allow any 3rd party plugin to replace the stock GPS and there is nothing we can do: the X-Plane dev kit doesn't provide any service for this. Please note: a G1000 EFIS is also a GPS and this is not meant to be used with another GPS but the one embedded.

Can you try with the default Baron instead?

 

 

Quote

 

Bill_S:

Thanks for replying.  Yes, realsimgear, 530 and 430 pair with the RXP SW update.

I am using stock C172 with same 530/430 pair as per the x-plane layout with these two avionics boxes.

 

 

 

[RamonB 449]

Don't know anything about XP, but there is an easy fix for FSX/P3D.

In an xml gauge <Update>
When You detect that the GPS is not driving NAV1 (Because the GTN switched to VLOC), you auto set the course in the HSI to the VOR or LOC/ILS bearing. You can also auto switch to APR.
I'll post my code when I get home. Perhaps someone can translate it to XP code.

Edited July 17, 2020 by RamonB

[RamonB 449]

OK, here is some code, abbreviated as it is part of a much larger project.

Please note:
This snippet just aligns the CRS in the HSI when the GTN switches to VLOC. It assumes You have valid NAV sources in GPS and NAV1 radio.
I advise You check for valid NAV sources beforehand and set a var to enable or disable auto switching.

What it does is: Align the CRS, and if NAV1 signal is invalid it sets ROL-PIT mode.
Only var I added to this snippet is the (L:AP_NAV_CTRL, number) so the inner code only executes when there is an actual GPS -> NAV switch.

 

<Update id="GPS_NAV_SWITCH">
	<script>
	(A:GPS DRIVES NAV1, bool) ! (L:AP_NAV_CTRL, number) 1 == and
	if{
		0 (&gt;L:AP_NAV_CTRL, number)
	
		(A:NAV HAS NAV:1, bool)
		if{
			(&gt;K:HEADING_GYRO_SET) (* Center the GYRO, optional *)
			(A:NAV HAS GLIDE SLOPE:1, bool)
			if{
				(A:NAV HAS LOCALIZER:1, bool)
				if{ (A:NAV LOCALIZER:1, degrees) (&gt;K:VOR1_SET) }
				els{ (A:PLANE HEADING DEGREES MAGNETIC, degrees) (&gt;K:VOR1_SET) }
			}
			els{ (A:NAV RADIAL:1, degrees) 180 - dnor (&gt;K:VOR1_SET) }
		}
		els{
			<!-- NO VALID NAV. SO, SET SEFAULT ROL & PIT -->
			(A:AUTOPILOT FLIGHT DIRECTOR ACTIVE, bool)
			if{
				(&gt;K:AP_ATT_HOLD_ON)
				(&gt;K:SYNC_FLIGHT_DIRECTOR_PITCH) 
			}
		}
	} els{ 1 (&gt;L:AP_NAV_CTRL, number) }
	</script>										
</Update>

Hope it helps.

Cheers.

[Bill_S 0]

Thank you.   I tried one suggestion with a limited approach.   I’ll trial these tomorrow ((Sunday)