NAV mode keeps changing to ROL with Non-GPS Avionics
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I decided to try a VOR only trip in Alaska, with two KX 155Bs. Passenger version if it matters.
When in NAV mode tracking a VOR, the Autopilot keeps changing to ROL mode for no apparent reason. I change it back to NAV, it stays for maybe 20-40 seconds, then goes back to ROL. HDG mode persists.
This is with today's 1.1 update. I'd not tried flying old-skool on the initial version.
Can anyone else repro? Pilot error? I've never seen this on any BKSQ aircraft before. And never had this using TDI GTN units either
I can post a video to demo if that would be helpful.
@SteveKane Where in Alaska were you flying, and which VORs did this happen on? Could be due to altitude, and losing signal due to terrain? I tend to fly relatively low in a lot of Alaska, for the views, so I see similar behavior pretty often when terrain blocks a VOR signal.
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@SteveKane Where in Alaska were you flying, and which VORs did this happen on? Could be due to altitude, and losing signal due to terrain? I tend to fly relatively low in a lot of Alaska, for the views, so I see similar behavior pretty often when terrain blocks a VOR signal.
@RPGamerous It was from PAWG Wrangell to PAKT Ketchikan. VOR used was mainly Level Island 116.5. Cruise was at 7000 ft. However, It also reverted to ROL when I was on the ILS 11(?) approach into PAKT. Made it interesting with IFR conditions until 500' AGL, lol.
As mentioned above, also got similar behavior in the Duke, where it switched to HDG mode instead.
I tried monitoring some of the BKSQ VOR-Related LVARs in SPAD; I might dig into that a bit more to look for a pattern.
I briefly tried the same flight in the BaE 146, no cutouts, but that was late.
I'll try things again tonight.
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@RPGamerous It was from PAWG Wrangell to PAKT Ketchikan. VOR used was mainly Level Island 116.5. Cruise was at 7000 ft. However, It also reverted to ROL when I was on the ILS 11(?) approach into PAKT. Made it interesting with IFR conditions until 500' AGL, lol.
As mentioned above, also got similar behavior in the Duke, where it switched to HDG mode instead.
I tried monitoring some of the BKSQ VOR-Related LVARs in SPAD; I might dig into that a bit more to look for a pattern.
I briefly tried the same flight in the BaE 146, no cutouts, but that was late.
I'll try things again tonight.
@SteveKane Where on the ILS did it revert from? Were you on APCH mode then it reverted? Were you in HDG to intercept before it reverted (ie as you captured the localizer)? I'm wondering if the issue may be tracked down to which modes are active vs supposed to activate. I'm just curious.
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@RPGamerous It was from PAWG Wrangell to PAKT Ketchikan. VOR used was mainly Level Island 116.5. Cruise was at 7000 ft. However, It also reverted to ROL when I was on the ILS 11(?) approach into PAKT. Made it interesting with IFR conditions until 500' AGL, lol.
As mentioned above, also got similar behavior in the Duke, where it switched to HDG mode instead.
I tried monitoring some of the BKSQ VOR-Related LVARs in SPAD; I might dig into that a bit more to look for a pattern.
I briefly tried the same flight in the BaE 146, no cutouts, but that was late.
I'll try things again tonight.
@SteveKane Yeah then probably not related to altitude and terrain, I think between Wrangell and Ketchikan LVD should be easily tracked at 7000ft. I'll do some VOR flights of my own and see how it goes.
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@SteveKane Where on the ILS did it revert from? Were you on APCH mode then it reverted? Were you in HDG to intercept before it reverted (ie as you captured the localizer)? I'm wondering if the issue may be tracked down to which modes are active vs supposed to activate. I'm just curious.
@plicpriest1 said in NAV mode keeps changing to ROL with Non-GPS Avionics:
@SteveKane Where on the ILS did it revert from? Were you on APCH mode then it reverted? Were you in HDG to intercept before it reverted (ie as you captured the localizer)? I'm wondering if the issue may be tracked down to which modes are active vs supposed to activate. I'm just curious.
I don't quite remember, as I was more trying to focus on landing in IMC. I think I was in HDG mode angled towards the ILS, and I pushed APR. It captured, but soon switched to ROL mode.
I'll try to repro things later today.
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@RPGamerous It was from PAWG Wrangell to PAKT Ketchikan. VOR used was mainly Level Island 116.5. Cruise was at 7000 ft. However, It also reverted to ROL when I was on the ILS 11(?) approach into PAKT. Made it interesting with IFR conditions until 500' AGL, lol.
As mentioned above, also got similar behavior in the Duke, where it switched to HDG mode instead.
I tried monitoring some of the BKSQ VOR-Related LVARs in SPAD; I might dig into that a bit more to look for a pattern.
I briefly tried the same flight in the BaE 146, no cutouts, but that was late.
I'll try things again tonight.
@SteveKane said in NAV mode keeps changing to ROL with Non-GPS Avionics:
I tried monitoring some of the BKSQ VOR-Related LVARs in SPAD; I might dig into that a bit more to look for a pattern.
Just trying to save you some time as you're looking into this, the signal degradation system is "for your eyes only" and has nothing to do with the autopilot behavior. You might still find some useful information from the L:Vars, but none of it will be causal. Just trying to help, since you're willing to look into this!
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@SteveKane said in NAV mode keeps changing to ROL with Non-GPS Avionics:
I tried monitoring some of the BKSQ VOR-Related LVARs in SPAD; I might dig into that a bit more to look for a pattern.
Just trying to save you some time as you're looking into this, the signal degradation system is "for your eyes only" and has nothing to do with the autopilot behavior. You might still find some useful information from the L:Vars, but none of it will be causal. Just trying to help, since you're willing to look into this!
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@SteveKane said in NAV mode keeps changing to ROL with Non-GPS Avionics:
I tried monitoring some of the BKSQ VOR-Related LVARs in SPAD; I might dig into that a bit more to look for a pattern.
Just trying to save you some time as you're looking into this, the signal degradation system is "for your eyes only" and has nothing to do with the autopilot behavior. You might still find some useful information from the L:Vars, but none of it will be causal. Just trying to help, since you're willing to look into this!
@Black-Square said in NAV mode keeps changing to ROL with Non-GPS Avionics:
Just trying to save you some time as you're looking into this, the signal degradation system is "for your eyes only" and has nothing to do with the autopilot behavior.
Anecdotally, I have seen this. How does/would a real autopilot handle that sort of signal oscillation?
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@Black-Square Thanks for the 411.
Is there an LVAR I can monitor that'll show whether the KAP140 Autopilot is in "ROL" mode?
@SteveKane You can find all of the relevant SimVars here. For roll mode, I would monitor both
AUTOPILOT BANK HOLDandAUTOPILOT WING LEVELER. I'm not sure exactly when one is activated over the other, so I just monitor both in all my code. -
I've been doing some testing. The plot thickens:
- This behavior happens in either dual KX 155B units, or TDS GTN750/650 when in VLOC mode.
- It happens everywhere, not just Alaska.
- The same behavior happens in the Duke, though it changes from NAV to HDG mode. This behavior is across models, which we know from the Starship thread.
- When in GPS mode, everything works fine, as I'd expect.
- Here's where it gets interesting. I use SPAD for all of my planes. For a test, I restarted the sim, spawned the 208 on the runway, did NOT launch Spad but instead "moused it" for everything. No issues whatsoever, stayed in NAV tracking a VOR, departing KPHX 07L, and simply tracking the nearby PXR VOR to the east for 45+ miles.
- Turned around back to PXR, started Spad, briefly switched from NAV to HDG back to NAV just for kicks, and a couple of minutes later, ROL mode.
- In SPAD, I've tried both the standard "K:AP_xxx" events as well as the "H:KAP140_PUSH_xxx" commands for NAV/HDG/etc., no difference: I get ROL mode using each.
- If I start a test flight using SPAD, eventually get the NAV->ROL, and I turn off SPAD, the NAV->ROL issue still occurs.
It seems that simply starting SPAD (with my rather extensive profile) correlates with this behavior.
I'll look into this some more and report back, perhaps starting with an empty Spad profile and incrementally adding things.
(In the meantime, I also might write some Spad code to detect when it goes from NAV to ROL and have it go back to NAV, though that might have some unintended side effects)
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I've been doing some testing. The plot thickens:
- This behavior happens in either dual KX 155B units, or TDS GTN750/650 when in VLOC mode.
- It happens everywhere, not just Alaska.
- The same behavior happens in the Duke, though it changes from NAV to HDG mode. This behavior is across models, which we know from the Starship thread.
- When in GPS mode, everything works fine, as I'd expect.
- Here's where it gets interesting. I use SPAD for all of my planes. For a test, I restarted the sim, spawned the 208 on the runway, did NOT launch Spad but instead "moused it" for everything. No issues whatsoever, stayed in NAV tracking a VOR, departing KPHX 07L, and simply tracking the nearby PXR VOR to the east for 45+ miles.
- Turned around back to PXR, started Spad, briefly switched from NAV to HDG back to NAV just for kicks, and a couple of minutes later, ROL mode.
- In SPAD, I've tried both the standard "K:AP_xxx" events as well as the "H:KAP140_PUSH_xxx" commands for NAV/HDG/etc., no difference: I get ROL mode using each.
- If I start a test flight using SPAD, eventually get the NAV->ROL, and I turn off SPAD, the NAV->ROL issue still occurs.
It seems that simply starting SPAD (with my rather extensive profile) correlates with this behavior.
I'll look into this some more and report back, perhaps starting with an empty Spad profile and incrementally adding things.
(In the meantime, I also might write some Spad code to detect when it goes from NAV to ROL and have it go back to NAV, though that might have some unintended side effects)
@SteveKane Very interesting results!! I will eagerly await more testing! This could explain why I have never seen this, since I don't use any 3rd party hardware applications that might be polling the variables or causing whatever hiccup is related to this in MSFS 2024.
