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MSFS Autopilot settings

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france
I made a quick video to illustrate a problem I encountered, it is here:
As you can see, the automatic ILS approach with autopilot is not perfect at all. It looks OK at the beginning, but as the aircraft gets closer to the runway, the autopilot deviates from the FD, which is corrected only when I take back controls manually. It is strange because the FD looks OK but the autopilot does not follow the FD as it should.

This makes me think of a bad configuration of the PID that is probably used in the AP to follow the FD. Do you know if there is a way to fix this through settings in some files?
As far as I remember, in FSX there was some values that could be adjust in the aircraft.cfg file to fix this kind of thing.
In MSFS, I found there is an [AUTOPILOT] section in the systems.cfg file, do you think it is the right part to edit?
(I never did this before)

Thanks for your help,
Eric
 
Additional information:
I found what I was talking about in the FSX C172 aircraft.cfg file, in the [AUTOPILOT] section:
nav_proportional_control=9.00
nav_integrator_control=0.25
nav_derivative_control=0.00
nav_integrator_boundary=2.50
nav_derivative_boundary=0.00
gs_proportional_control=9.52
gs_integrator_control=0.26
gs_derivative_control=0.00
gs_integrator_boundary=0.70
gs_derivative_boundary=0.00
I never played with these values but I understand these are the PID settings for the different AP modes.
Is this also available in MSFS?
 
Sorry Guys, I am doing questions and answers at the same time...
Looking again at the video, it appears that the autopilot does follow the FD, but the FD is wrong !! The FD are perfectly centered while the aircraft deviates from the localizer and later from the glideslope. So I'm afraid the problem cannot be solved by adjusting the autopilot PID settings.

Any idea to solve this problem?

Thanks,
Eric
 
So far as I am aware, in previous sims the derivative entries in the C172 aircraft.cfg file do nothing and should not have been there. They only come into play when the aircraft is an AI object. I doubt there's been any change in FS2020 but I'm more than happy to be corrected.
 
Ok, I watched the video. Here's what I see:

1. The needle is accurate. It is correctly showing that you are slowly coming in left of the runway's centerline. However, there's more to this... read on! :)
2. The aircraft's "center" for the ILS signal appears to run down the middle of the pilot's seat. It should instead be on the center of the aircraft. When you turned the autopilot off and adjusted the aircaft to center on the lateral deviation, you ended up with the center of the runway underneath the pilot. The center of the runway, when landing, is preferred to be under the center of the aircraft.. not the left-hand seat.

So, what I see in that video is an autopilot that comes down slightly left of the FD, and somehow the FD is tied to the visuals because it's centered when the left-hand seat is aligned on the runway centerline... which is inaccurate.

Hopefully I explained that well enough.
 
Ok, I watched the video. Here's what I see:

1. The needle is accurate. It is correctly showing that you are slowly coming in left of the runway's centerline. However, there's more to this... read on! :)
2. The aircraft's "center" for the ILS signal appears to run down the middle of the pilot's seat. It should instead be on the center of the aircraft. When you turned the autopilot off and adjusted the aircaft to center on the lateral deviation, you ended up with the center of the runway underneath the pilot. The center of the runway, when landing, is preferred to be under the center of the aircraft.. not the left-hand seat.

So, what I see in that video is an autopilot that comes down slightly left of the FD, and somehow the FD is tied to the visuals because it's centered when the left-hand seat is aligned on the runway centerline... which is inaccurate.

Hopefully I explained that well enough.
I think I understood your explanations but I think you're wrong. I agree, the ILS is aligned on the aircraft center, which is not exactly the position of the pilot seat, this is definitely true. But it is not the problem here. The problem is that I am flying on autopilot with APPR mode engaged to follow the localizer and the glideslope, and it appears the autopilot does not do its job. I mean you see the lateral deviation, the aircraft is slightly on the left of the localizer path, and the autopilot does not correct the trajectory to get back on the ideal path, the FD bars are still perfectly centered as if the current trajectory was perfect, which is not the case.. Same for the glideslope, the green diamond moves up, showing the aircraft is below the glide path and should pitch up, but nothing happens, the FD bars still centered, the trajectory is not corrected.
What I mean here is that it is not related to what the pilot sees or where the pilot is, it is just related to the way the autopilot works, not very well in that case...

It is now my turn to say I hope my explanations are clear :)
 
Eric, if you are manually flying the ILS, and you're on the needle... and your eyepoint is running down the runway centerline in an aircraft with a seat that is left of the aircraft's centerline... then there is something completely wrong with that. It doesn't work that way in a real aircraft.
 
Eric, if you are manually flying the ILS, and you're on the needle... and your eyepoint is running down the runway centerline in an aircraft with a seat that is left of the aircraft's centerline... then there is something completely wrong with that. It doesn't work that way in a real aircraft.
This time I am not sure I fully understand what you say... But the point of this post and the video I shared is just about the way the autopilot flies the approach. Even if you couldn't see anything outside the aircraft, you would still see there is a problem. Just look at the localizer needle, you can see it deviates to the right and the autopilot does not correct the deviation, this has nothing to do with the pilot point of view.
To better understand what I mean, focus on the PFD only:

1618342448003.png


On this image extracted from the video, you can see the localizer needle is not centered, which means the aircraft is not on the localizer path, but the FD bars are centered which means the AP is OK with this. This IS the problem.

Eric
 
Yes, that I understand... however...

When you hand flew to correct, by the time you had the needle centered... the nose gear of the aircraft was to the right of the centerline. I state this because your viewpoint was centered down the runway and your actual position in the aircraft was to the left of the nose gear. The nose gear should have been in line with the ILS needle and it's to the right.

There is a problem there.
 
Ed,

When the aircraft is properly aligned with the center of the ruwnay, the centerline coincides with the pilot AND copilot's viewpoints. The nose gear will be also aligned with the centerline.
Take a look at this picture, pilot view/copilot view and external view.

Centerline.jpg


Tom
 
The standard view is a cyclops. That is why the view appears much more interrupted than for real when you can partially "see around" the windshield structure. It does not look real except for a single seater view on the airplane centerline.
Roy
 
Yes, that I understand... however...

When you hand flew to correct, by the time you had the needle centered... the nose gear of the aircraft was to the right of the centerline. I state this because your viewpoint was centered down the runway and your actual position in the aircraft was to the left of the nose gear. The nose gear should have been in line with the ILS needle and it's to the right.

There is a problem there.
You're absolutely right. This was not the point of my post but you are right, which means there are 2 problems shown here :)
 
That view is flawed... I don't recall having that issue in FSX/Prepar3D.
No flawed at all. Though not exact, it is pretty much similar to the vision in a real aircraft. When the centerline of a runway (or taxiway) is aligned with either pilot's viewpoint, the nose gear is as well.
which means there are 2 problems shown here
I only see one problem, the FD bars not properly guiding the approach. The other statement is not correct, in the video I see the needle is centered when the pilot's viewpoint is centered on the runway (which IS correct ). Next picture is a real NAV landing, copilot's side, in where the aircraft is perfectly aligned with the center of the ruway, as shown in the PFD.

Centered.jpg




Tom
 
My opinion, this is not caused by the airplane or autopilot. The reason is in the scenery. Try to fly different airports and compare the results.
As developer I had the same issue with my airport during Airbus approaches. Then I optimized the ILS settings in my airport and it fits perfect.
 
If you are in the left seat and do a perfect approach, the ILS indications on both sides of the cockpit will be identical and centered. However, looking forward, the left seat pilot will see he is left of the centerline and the right one will be right of the centerline. That makes the airplane land exactly on the center of the runway. The ILS display is the same on both sides of the airplane, so both pilots see a centered approach on the display.
Roy
 
My opinion, this is not caused by the airplane or autopilot. The reason is in the scenery. Try to fly different airports and compare the results.
As developer I had the same issue with my airport during Airbus approaches. Then I optimized the ILS settings in my airport and it fits perfect.
I wrote this post a while ago. some time passed since then and I learnt a lot about the aircraft settings. I confirm the problem you see on the video is because of poor PID settings in the aircraft configuration files. I am working on a custom aircraft that also had wrong behavior regarding ILS, I adjusted the PID settings used to guide the aircraft on ILS and it now works perfectly, making it able to autoland.
 
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