Localizer is way off on the Dynon HDX HSI from SL30 Signal

Hbadawi

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Sep 22, 2022
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Hi There:

Here is my setup: 2 HDX 10”, Garmin GPS 175 and a Garmin SL30. Arinc 429.

I have been trying to get the Dynon Autopilot to fly via a GPS set course on the 175 until the final approach course (say via vectors), then have the HDX auto switch to the nav 2 signal, which in this case happens to be the SL30 which would be tuned to the local localizer frequency.

Problem 1:

I am not able to get the HDX to AUTO SWITCH. I did set the value to YES (Label 1000P) in the Arinc 429 setup. By the way my Arinc 429 shows only one NAV source which is the GPS 175. When I try to add a NAV 2 source for the SL30, which I think is set up as serial port 2, it shows up RED and does not bring up the label. Not sure if that is the correct setup or not.

Problem 2:

Because the auto switch does not happen when i hit the FAF of an ILS approach, i switch the NAV 1 source on the HDX to the SL30 (which has the localizer frequency tuned in) manually. I get the glide slope indicator, but for some reason the localizer seems to be off. It shows the plane to the right of it, and if on AUTO Pilot, the plane starts to turn to the right trying to intercept the localizer even though I am looking straight down at the runway.

My local avionics guy thinks we need to calibrate the SL30 but from what I am reading online, that thing is bullet proof and hardly ever needs to be calibrated.

What am I doing wrong?
 
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Carl_Froehlich

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It would help if you provided information on how you wired both the GPS-175 and SL-30 to the ARINC.

Does the SL-30 nav drive the CDI when just tracking a VOR?

Look starting at page 12-6 of the install manual. Are you wired and configured as it discusses?

Carl
 

Hbadawi

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It would help if you provided information on how you wired both the GPS-175 and SL-30 to the ARINC.

Does the SL-30 nav drive the CDI when just tracking a VOR?

Look starting at page 12-6 of the install manual. Are you wired and configured as it discusses?

Carl
My 175 is connected directly to my ARINC while the SL30 is connected via a serial port to the HDX. The SL30 does drive the CDI when tracking the VOR.
 

Dynon

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1) Not positive on this, but I think the auto-switch only work with devices that have both the NAV and GPS in the same device. IE, GTN/GNS/IFD type devices that have the nav radio option. Or, the SL30 may need to be configured with the GPS 172 so it's aware of it (not sure if that's possible or not).

2) You do need to set the localizer course manually on SkyView. But that might not be it. If you had a picture of the representative behavior, that would help see what you're seeing.
 

Hbadawi

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1) Not positive on this, but I think the auto-switch only work with devices that have both the NAV and GPS in the same device. IE, GTN/GNS/IFD type devices that have the nav radio option. Or, the SL30 may need to be configured with the GPS 172 so it's aware of it (not sure if that's possible or not).

2) You do need to set the localizer course manually on SkyView. But that might not be it. If you had a picture of the representative behavior, that would help see what you're seeing.
So yes I am realizing that the auto switch can not happen as the connections to the hdx do not happen via Arinc. So I can just manually switch the nav source as I get to the faf.

What do you mean by setting the localizer course manually? By the way the antennas are at the bottom of the plane fairly centered.
 

RVDan

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You have to set the localizer inbound course on the cdi bearing or the CDI needle will be off. Another person I know has the GPS175 and SL30. They have to manually switch the hsi source and dial in the inbound course. I only have the SL 30 and have the issue of manually setting the CDI inbound course. The SL30 does not have the inbound course data and neither does the HDX so it needs to be set manually. This is a main benefit of having a GNS or IFD, the transition happens inside the GNS or IFD.
 

Hbadawi

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You have to set the localizer inbound course on the cdi bearing or the CDI needle will be off. Another person I know has the GPS175 and SL30. They have to manually switch the hsi source and dial in the inbound course. I only have the SL 30 and have the issue of manually setting the CDI inbound course. The SL30 does not have the inbound course data and neither does the HDX so it needs to be set manually. This is a main benefit of having a GNS or IFD, the transition happens inside the GNS or IFD.
Thanks for the reply. So I get how you have to manually switch between the 175 and the sl30. But what do you mean you have to manually set the CDI inbound course? I just put in the ILS frequency in the sl30 and the green arrow should show up correctly on the HDX?
 

RVDan

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With the SL30 as your HSI source you have to use the course knob to set the CDI needle to the inbound course. It does not do this automatically. If on the AP, you need to be quick or the AP starts to go after the CDI needle for the localizer which is not correct until you have the inbound course set.
 

Dynon

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Thanks for the reply. So I get how you have to manually switch between the 175 and the sl30. But what do you mean you have to manually set the CDI inbound course? I just put in the ILS frequency in the sl30 and the green arrow should show up correctly on the HDX?
SkyView's HSI will point in whatever direction you have the CRS set to. The CDI will be correct per the localizer, but you need to have the HSI set in the right direction. Simple case: your localizer is 360. You have it tuned and you're right of course (needle to the left). If you have SkyView's HSI course set to 90, for example, the HSI picture will be rotated 90 degrees, and it'll LOOK LIKE the course is rotated.
 

CanardMulti

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To enlarge upon and, for some, perhaps clarify the above:

When tracking a VOR, the number in the course window matters. If the pilot changes the course, the CDI needle deflection will also change because the displacement of the needle represents how many degrees you are displaced from the selected course radial.

With an ILS depicted on an HSI, however, the CDI *does not care* what number is in the course window. Having the correct front course entered into the HSI course window does indeed make the pilot's visualization and therefor situational awareness much better, which is after all why folks spend the $$$ to install an HSI in the first place. For an ILS, the CDI's job is to depict the difference in strength the antenna sees between the installation's left side signal and right side signal for whatever frequency is selected in the VHF NAV radio. When the left and right side signals are equal, the CDI is centered. The course is essentially baked in already for any given ILS installation. I've demonstrated this to students many times (on a mechanical HSI) by spinning the HSI course knob while on an ILS without the CDI changing deflection. I freely admit that I have not tried it w/ Skyview, but I'd be at least modestly surprised if it was different from my antiquated experience with many a mechanical HSI.

Ken
 

RVDan

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SkyView's HSI will point in whatever direction you have the CRS set to. The CDI will be correct per the localizer, but you need to have the HSI set in the right direction. Simple case: your localizer is 360. You have it tuned and you're right of course (needle to the left). If you have SkyView's HSI course set to 90, for example, the HSI picture will be rotated 90 degrees, and it'll LOOK LIKE the course is rotated.
This is correct but not complete. When the CRS window is not set for the correct inbound course, the localizer cdi needle will not be correct. Several of us flying Dynon Classic and HDX have verified this. One would think that the localizer needle would not be affected by the CRS setting but it is.
 

Shary

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Jul 19, 2023
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This is correct but not complete. When the CRS window is not set for the correct inbound course, the localizer cdi needle will not be correct. Several of us flying Dynon Classic and HDX have verified this. One would think that the localizer needle would not be affected by the CRS setting but it is.
And you can add me as an additional pilot who will verify that if the CRS is NOT set to the course on the approach plate, the CDI will NOT read correctly.
(Use the lower left knob (or touch the COURSE window), select CRS (rather than HDG, or such) and dial into the CRS window the approach course)
 
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