MU-2 Marquise v2 - HDG only latches on APU power, drops when APU is removed

[jrsaez82]

Hi everyone,

I’m posting this here in case another user has already seen the same issue and found a workaround before support replies.

I bought the TOGA Simulations MU-2 Marquise v2 for XP12 and I’m having a strange AFCS / HDG / autopilot problem.

I want to be clear that I’m not posting this as a “quick question” without checking first. I have already:

• searched through forum threads
• read the available documentation
• watched videos
• tested different startup sequences
• reinstalled the aircraft
• checked bindings and controls
• and I have already opened a support ticket with X-Aviation

After a lot of testing, this is what I have been able to isolate:

• HDG does not latch on battery power only
• HDG does latch when the aircraft is powered from the APU
• HDG can remain latched with APU on, even after both engines are started and the condition levers are advanced to takeoff
• but the moment I remove APU power, HDG immediately disconnects
• because of that, the AP becomes unreliable or unusable

So at this point it looks less like a normal “how to use the autopilot” problem and more like an AFCS electrical power / bus transfer / plugin initialization issue.

I also found some related threads, but none of them gives me a final answer for this exact behavior.

Has anyone here seen this?

Especially this exact pattern:

battery only = no HDG
APU on = HDG works
APU off = HDG drops

Any hint would be very appreciated.

Thanks a lot.

[tkyler]

@jrsaez82

I'll dig into this, this may be due to a bus-tie bug I discovered recently and reported/addressed only a week ago, which was confirmed.

When you try and enable the HDG mode, does it blink briefly?  ...and just not stay engaged?  I can confirm that my code attempts to set the HDG mode, but X-Plane immediately disconnects it so that is the point of investigation.

I am also slightly confused by your "APU on = HDG works"...first, there is no APU, only a GPU (which I'll assume is what you meant) and if I connect that, HDG certainly does not just work....do you mean "GPU connected + battery switch on"?  + inverter on?   etc.  

Also, which aircraft?  a Garmin variant?  or OEM?  the presence of GPSS with the Garmin's affect some AP settings.

For me....I'm seeing the "blinking" HDG, but after engine start, it stays on.  This may be an "X-Plane" thing I'd have to talk to Philipp about.  I'm still poking around.  It could also be a threshold voltage issue.   I'm pretty sure I'll have to ping Philipp on this one.   I know he frequently "improves" the default X-Plane stuff, which clashes with our customizations as users update.

 

 

Edited 1 hour ago by tkyler

[jrsaez82]

31 minutes ago, tkyler said:

@jrsaez82

I'll dig into this, this may be due to a bus-tie bug I discovered recently and reported/addressed only a week ago, which was confirmed.

When you try and enable the HDG mode, does it blink briefly?  ...and just not stay engaged?  I can confirm that my code attempts to set the HDG mode, but X-Plane immediately disconnects it so that is the point of investigation.

I am also slightly confused by your "APU on = HDG works"...first, there is no APU, only a GPU (which I'll assume is what you meant) and if I connect that, HDG certainly does not just work....do you mean "GPU connected + battery switch on"?  + inverter on?   etc.  

Also, which aircraft?  a Garmin variant?  or OEM?  the presence of GPSS with the Garmin's affect some AP settings.

 

For me....I'm seeing the "blinking" HDG, but after engine start, it stays on.  This may be an "X-Plane" thing I'd have to talk to Philipp about.  I'm still poking around.

 

 

Thanks a lot, that is actually very helpful.
 

- Yes, when I try to enable HDG, it does blink briefly and then does not stay engaged.

- Also, you are correct: I incorrectly said APU, but I actually meant GPU / external power.

- My test case is with the 4-bladed GNS / Garmin variant.

- What I observed is this:

1.- With ther aircraft with on battery power only, HDG does not latch.

2.- With GPU connected (without batteries on) HDG can latch on the ground. And the aircraft powered up, after engine start, HDG can still remain engaged but when I remove GPU/external power, HDG drops out immediately after a couple os seconds.

 

So the behavior really seems tied to the electrical source / bus transfer.

 

I can keep testing and provide a more exact switch-by-switch sequence if that helps, but from my side it definitely looks like X-Plane is dropping HDG right after the command is sent.

 

Thanks again for looking into it.

[tkyler]

@jrsaez82  I know its been a long time since i've messed with the MU-2, but I expect to come back around to it within the next 2 months and start pointing it to the future.  I'll make an announcement and explain the timings and future at that time.   There is a lot of really good and positive developments going on behind the scenes at Laminar, which I'm involved in....and for the better.  Quite a bit has changed with regards to the flight model and electrical system models and I fully suspect that Philipp may have put some type of criteria on enabling the various AP modes based on more advanced "amp flow" and voltage models that he implemented well after I coded these systems up....so its absolutely incumbent upon me to find out what those are and bring this thing up to speed.  

As silent as i've been here, I honestly have never been more involved with X-Plane than I am today....and I am fortunately being able to contribute to overcoming the impediments that have historically caused delay headaches for devs forever, including me.  We've been asking the questions internally,  "what slows devs down and makes it hard to update and test" and are engineering solutions for that....something that has been sorely needed for a long time.

 

[jrsaez82]

35 minutes ago, tkyler said:

@jrsaez82  I know its been a long time since i've messed with the MU-2, but I expect to come back around to it within the next 2 months and start pointing it to the future.  I'll make an announcement and explain the timings and future at that time.   There is a lot of really good and positive developments going on behind the scenes at Laminar, which I'm involved in....and for the better.  Quite a bit has changed with regards to the flight model and electrical system models and I fully suspect that Philipp may have put some type of criteria on enabling the various AP modes based on more advanced "amp flow" and voltage models that he implemented well after I coded these systems up....so its absolutely incumbent upon me to find out what those are and bring this thing up to speed.  

As silent as i've been here, I honestly have never been more involved with X-Plane than I am today....and I am fortunately being able to contribute to overcoming the impediments that have historically caused delay headaches for devs forever, including me.  We've been asking the questions internally,  "what slows devs down and makes it hard to update and test" and are engineering solutions for that....something that has been sorely needed for a long time.

 

Hi again, 

 

Thanks for the detailed reply, I really appreciate it.

That makes sense, and it also matches what I have been seeing on my side: the issue appears to be strongly tied to electrical source / bus behavior rather than to autopilot usage itself.

In my testing, HDG will not latch on battery power only, it can latch with GPU power, and it drops again when GPU power is removed, so your explanation about newer electrical / amp-flow criteria in X-Plane sounds very plausible.

Thanks again for confirming that this is something worth investigating. I bought the aircraft four days ago, and I’m really disappointed not to be able to fly it (unless it’s in manual mode, which is tricky for flights longer than 20 minutes).

 I’ll keep an eye on future announcements and I’m happy to provide any additional test details if that helps when you come back to the MU-2.