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Old 01-11-2019, 12:47 PM   #21
QuiGon
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Quote:
Originally Posted by renhanxue View Post
The manual matches what's in the flight manual for the real aircraft, which states (in my translation)


This course hold is not supposed to level the plane in pitch, though.
Thanks, that made it more clear!

I agree with Holton181, that it seems to be not working correctly in DCS now, as the Viggen does drift off course.
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Old 01-11-2019, 01:10 PM   #22
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Originally Posted by Holton181 View Post
Good one, thanks. Then I guess the implementation of the course hold is bugged.
Yep, as I said previously, I think we can all agree that this is not working as per (both) manuals!
Again I'll say it would be good to get some contributions from devs on this and other issues that have been raised recently.
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Old 01-12-2019, 08:08 PM   #23
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Just tested the course and pitch hold in HÖJD mode during a 300km flight over water. And I must say it does seem to work. I didn't test the <7°-return-to-course behavior thoroughly, but focused on leveling out and pitch. It held bank, pitch, course and altitude rock solid.
BUT! it is incredibly sensitive about getting your stick and pedals centered. Touching them an itsy bitsy tiny bit and you start to drift. Toggling HÖJD off and on stabilized the bird again, but obviously at a slightly different altitude and course. To make sure it didn't just work because I had really made an effort centering my controls, I disabled HÖJD while zoomed in on the flight path vector and observed that it did bank and pitch slowly. Engaged HÖJDand it stabilized. Disabling again and it started to bank and pitch exactly the same as before. Turned HÖJD off and on several times and observed the same behavior. Then for fun I adjusted my controls very slightly and finally succeeded to get it stabilized merely by the controls and only SPAK.

I did briefly test the <7°-return-to-course by moving either stick or pedals just a notch, but could not observe any stabilizing nor return to previous course, but then again I can't guarantee that I was within <7°.
I also in the beginning reduced power from first stage AB to just disabling it with HÖJD active, with no change in attitude or altitude.


Note!
I have a "full length" helicopter HOTAS (PFT Lynx) with no springs or detents, enough friction on all axes to let go in any position and with small angle, 12 bit Hall sensors (12 bit controller board) on all of them, effectively giving me more than 11bit real and noise free resolution on my stick. Due to the sensitivity of the axis in the Viggen, I assume low resolution controllers and/or noisy pots can make life pretty hard with these things.
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Old 01-12-2019, 08:20 PM   #24
imacken
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Quote:
Originally Posted by Holton181 View Post
Just tested the course and pitch hold in HÖJD mode during a 300km flight over water. And I must say it does seem to work. I didn't test the <7°-return-to-course behavior thoroughly, but focused on leveling out and pitch. It held bank, pitch, course and altitude rock solid.
BUT! it is incredibly sensitive about getting your stick and pedals centered. Touching them an itsy bitsy tiny bit and you start to drift. Toggling HÖJD off and on stabilized the bird again, but obviously at a slightly different altitude and course. To make sure it didn't just work because I had really made an effort centering my controls, I disabled HÖJD while zoomed in on the flight path vector and observed that it did bank and pitch slowly. Engaged HÖJDand it stabilized. Disabling again and it started to bank and pitch exactly the same as before. Turned HÖJD off and on several times and observed the same behavior. Then for fun I adjusted my controls very slightly and finally succeeded to get it stabilized merely by the controls and only SPAK.

I did briefly test the <7°-return-to-course by moving either stick or pedals just a notch, but could not observe any stabilizing nor return to previous course, but then again I can't guarantee that I was within <7°.
I also in the beginning reduced power from first stage AB to just disabling it with HÖJD active, with no change in attitude or altitude.
Thanks for that, but to be honest, it's not telling us anything new.
This thread is about ATT and it not returning to course after some drift or adjustment as the manual says it should.
I think we are happy the way that all other aspects of AP work except for that.
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Old 01-12-2019, 09:09 PM   #25
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Originally Posted by imacken View Post
Thanks for that, but to be honest, it's not telling us anything new.

This thread is about ATT and it not returning to course after some drift or adjustment as the manual says it should.

I think we are happy the way that all other aspects of AP work except for that.
But you said your self the course is drifting, didn't you? From OP:
Quote:
Originally Posted by imacken View Post
If I set ATT when on course for a waypoint, the Viggen just drifts way off course all the time, and I have to be permanently making adjustments.
In that respect ATT and HÖJD should act the same. They don't drift from course. My comment was about that part of your OP, not the returning to course (as I said I didn't get working either).
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Old 01-13-2019, 10:31 AM   #26
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Quote:
Originally Posted by Holton181 View Post
But you said your self the course is drifting, didn't you? From OP:

In that respect ATT and HÖJD should act the same. They don't drift from course. My comment was about that part of your OP, not the returning to course (as I said I didn't get working either).
Ah OK, I see what you mean. Sorry!
Yes, I'm not seeing the drifting I was talking about any more. I wonder if it was in a specific mission or set of circumstances.
Anyway, yes, you're right, that doesn't seem to be an issue.
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Old 01-13-2019, 10:39 AM   #27
Holton181
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Originally Posted by imacken View Post
Ah OK, I see what you mean. Sorry!

Yes, I'm not seeing the drifting I was talking about any more. I wonder if it was in a specific mission or set of circumstances.

Anyway, yes, you're right, that doesn't seem to be an issue.
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Old 01-13-2019, 01:28 PM   #28
Holton181
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I'm running a test for the return-to-course issue. Surprisingly enough it does seem to work! ...sort of...

Mind you, it is HIGLY sensitive on controller input and INCREDIBLY slow!

I attached the (very simple) mission I used, a start-in-air flight across the widest part of the Black Sea with x-tank and no wind, start with active pause. This is how I went about:
I opened DXTweak (controller management software) on my second monitor and made sure my stick and pedals was thoroughly centered (with an input value close to 32768 out of 65536).
Turned off my TrackIR.
Loaded the mission (in active pause) and activated HÖJD and noted indicated speed (about 850km/h).
Deactivated active pause and got a pitch jump, it did return to set pitch and altitude within a few seconds though. Heading was not affected. the steering dot stayed inside the FPV circle (not perfectly centered though, but steady).

Made sure to stabilize the speed at the original noted above and noted throttle input value in DXTweak for reference if repeating the test later. Kept it flying this way to make sure everything was stabilized. Adjusted seat height and zoom to bring the HUD to fill my main screen to really see even tiny changes.

Yanked the stick carefully to one side, the plane initiated a turn away from course, then returned the stick to center. All with an eye on DXTweak. The displacement was about 250-300 of the input value (less than 0.5% of 65536 or 1% of 32768 ). If the return-to-course would not work, the plane would settle at the new course it had at the moment I returned the stick to center, but it didn't, it returned slowly to previously established course towards the WP! I repeated this test several times with stick deflections of the same size but in both directions with the same result, slow return to course after recenter. It didn't return to EXACTLY the same course, but very close. With the history of Heatblure being very thorough about system modeling, I would not be surprised if they added some sort of small system errors causing this.

Next thing I tested was to keep the stick at said 250-300 deflection. At first the return-to-course didn't seem to work, but I let it go on. S..l..o..w..l..y.. the turn rate decreased, almost settled on a new course, then S..l..o..w..l..y..started to return to set course!
After a loooong time the course settled almost towards the WP. It was more off in relation to the WP than the previous tests, but I guess the return-to-cource isn't actually returning to the exact same track that should have been if no stick deflection, but rather just return to the same direction. In this case the return-to-cource was so slow that the plane shifted its position sideways quite much in relation to said track that it ended up quite far away but parallel to it.

My conclusion is that return-to-cource actually do work, but is WHAY to slow to make it practically usable. Remember that the deflections I used in this test was VERY small and performed very carefully, barely touched the stick. Imagine what bigger deflections would do.

The altitude hold on the other hand is fast enough to be usable. I get the impression that the issue with slow return-to-cource might be just a wrong order of magnitude of the scaling constant for the corrective signal (Δ-course) or the steering input for the control surfaces.
Attached Files
File Type: miz Course hold test No wind.miz (7.4 KB, 6 views)
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Last edited by Holton181; 01-13-2019 at 03:20 PM.
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Old 01-13-2019, 02:37 PM   #29
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Btw, how slow is slow, minutes?
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Old 01-13-2019, 02:49 PM   #30
Holton181
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Btw, how slow is slow, minutes?
Actually didn't time it, should have done when you mention it. For the small yanks where I returned to center (after 1-2s deflected, relative small change in course) about 10-15s, the ones were I kept the stick deflected maybe 10-15min, maybe more.
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