Pitch Oscillations and Uncoordinated flight

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pilotito84
Posts: 52
Joined: Mon Sep 11, 2017 3:47 pm
Location: Tucson, AZ

Pitch Oscillations and Uncoordinated flight

Post by pilotito84 »

I have a problem with Pitch Oscillations during cruise flights. On my climb outs everything looks normal until it reaches level off altitudes. For some reason the aircraft starts oscillating up and down around my altitude but the AP never seems to lock it and trim to hold that. It just keeps going up and down as much as +/- 1000 FPM. I have already reset the AP to defaults with no change. Also my aircraft never seems to maintain turn coordination during turns or even on straight and level flight neither on manual or AP. Any suggestions???

P.S. I took a picture and video but I didn't know how to load it
:oops:

MichaelYSSY
Posts: 744
Joined: Tue Jan 06, 2015 11:04 pm
Location: Sydney - Australia

Post by MichaelYSSY »

Hello there
Sorry didn't catch your name

What version of SA are you using?
P3D V?
FSUIPC V?
AIRCRAFT MODEL?

Could be a lot of things
Latest versions that I'm using seem stable at cruise alt level off

Cheers
Michael
SSTD 737
Sim-Avionics v1.96
P3D 4.5/5.0 HF1
FSUIPC 6.0.8

thomas747400
Posts: 101
Joined: Sun Feb 14, 2016 12:37 am
Location: Perth, Western Australia

Post by thomas747400 »

Hi Pilotito84

I fly the T777 and I experience the exact same issues you are having.


As for the oscillations, I am tinkering with the autopilot settings, I have had some promising signs with changing the Altitude Hold Accel Damping from -900 to -1200 but I have to do some more testing.


I am trying to identify the turn coordination issue myself perhaps we can compare some parameters:

P3D Autorudder >Off
Sim A PFC/ FBW Enabled > Off
TAC Enabled / Yaw Damper > On

Do I need to activate the Yaw Damper in the T7? I can't find a switch for that on the Overhead Panel.

I only have coordination issues at low altiudes < 5000ft. Above that, it is usually pretty good.

Thomas

pilotito84
Posts: 52
Joined: Mon Sep 11, 2017 3:47 pm
Location: Tucson, AZ

Post by pilotito84 »

Hi Michael, sorry about that i forgot to mention my specs. Im using P3D v4,
FSUIPC 5, and flying the T7 model. As for the SA i am using 1.9.

Francisco
Last edited by pilotito84 on Thu Oct 18, 2018 6:44 pm, edited 1 time in total.

pilotito84
Posts: 52
Joined: Mon Sep 11, 2017 3:47 pm
Location: Tucson, AZ

Post by pilotito84 »

Hello Thomas,
I’ll be more than happy to work with you in trying to figure out the problem. I have the same settings as you, and have tried it with FBW (even though the manual says that is not modeled) and yaw damper enabled with the same results.

As for the turn coordination i have the same symptoms as you. At lower altitudes is definitely more noticeable with the trim indicator deflecting almost completely. Up in higher altitudes it doesn’t deflect as much but deflects enough to be noticed.

Francisco

kand
Posts: 214
Joined: Wed Feb 03, 2016 3:48 pm
Location: Buckinghamshire, UK

Post by kand »

Does this occur in zero weather?

I had this with the 777, my problem turned out to be the turbulence setting, I disabled the P3d setting and also reduced the numbers in Activesky, my porpoising stopped after that.

thomas747400
Posts: 101
Joined: Sun Feb 14, 2016 12:37 am
Location: Perth, Western Australia

Post by thomas747400 »

Hi kand,

I have experienced these issues since upgrading to v1.9. Prior to that it was fine. I will do some testing in clear and wind free weather.

Cheers
Thomas

Fred
Posts: 156
Joined: Tue Mar 15, 2005 5:56 pm

Post by Fred »

Hi All

Since upgrading to 1.91 I am also having problems with pitch oscillations in level flight and in VNAV/LVL CHG ascents/descents (as described in the related previous thread).

A combination of the following here has seemed to help:

(1) ALT Hold Accel Damping -700 -> -1200

(2) In the aircraft.cfg file:

[flight_tuning]
elevator_effectiveness = 1.0 -> 0.7
aileron_effectiveness = 1.1 -> 0.7
rudder_effectiveness = 1.3 -> 1.1

In the couple of fair weather flight I have flown I have found this combination has eliminated the pitch oscillations in level flight. Also, VNAV descents now work smoothly. VNAV ascents have been improved significantly however there is still an issue with the first 30 seconds or so. In VNAV ascent the rate of climb initially rises slightly but then quickly swings into a negative rate, then followed by oscillations between positive/negative rate which gradually stabilize within 30-45 seconds. (Without the above mods those oscillations would never stabilize.)

I will be doing more testing on all this later today.

Using P3Dv1 and the SimA 737.

Fred K

Tankleader
Posts: 33
Joined: Fri Dec 23, 2016 8:12 am

Pitch Oscillations and Uncoordinated Flight

Post by Tankleader »

Hello All,

I am having the same issue. It seems to start randomly during the flight and ends with an uncontrollable aircraft.

Sim-Avionics Server= 1.90
P3D V=3.4.18.19475
FSUIPC V=4.974
WideServer= 7.1.5.1
AIRCRAFT MODEL= Ver 1.9 B777, FSX-Sim-Avionics-B777

When this occurs I select Alt-Tab and check to see what the server is doing. I've noticed that the Flt Data Rate 16 FPS and the A/P Rate 10 or 11 FPS drop to 1 FPS resulting in the lag causing the system to chase itself. This is just my observation in trying to figure out in what is happening. This issue has manifested itself in all 3 of my flights since I updated the other day.

Thanks
Andreas J Elesky

MichaelYSSY
Posts: 744
Joined: Tue Jan 06, 2015 11:04 pm
Location: Sydney - Australia

Post by MichaelYSSY »

Hi guys

Sorry to hear. I have the B737

Not getting this problem with 1.91 but it did happen with a previous SA version 1.8?

It was sorted out when it happened and I cant remember what the cause was? Something reminds me of YAW Damper issue? but AP frame rates could have been involved too.

Im sure Mark will sort it out quickly.

Oh, and Welcome to the Forum Francisco, sorry couldn't help you out on this one seems that B737 and B777 have different systems

Cheers
Michael
SSTD 737
Sim-Avionics v1.96
P3D 4.5/5.0 HF1
FSUIPC 6.0.8

Tankleader
Posts: 33
Joined: Fri Dec 23, 2016 8:12 am

Post by Tankleader »

MichaelYSSY wrote:Hi guys



Not getting this problem with 1.91 but it did happen with a previous SA version 1.8?


Cheers
Michael
Where is everyone getting 1.91 from? I just downloaded 1.9 from the link on the announcement page.

Thanks
Andy

Fred
Posts: 156
Joined: Tue Mar 15, 2005 5:56 pm

Post by Fred »

Fred wrote:Hi All

Since upgrading to 1.91 I am also having problems with pitch oscillations in level flight and in VNAV/LVL CHG ascents/descents (as described in the related previous thread).

A combination of the following here has seemed to help:

(1) ALT Hold Accel Damping -700 -> -1200

(2) In the aircraft.cfg file:

[flight_tuning]
elevator_effectiveness = 1.0 -> 0.7
aileron_effectiveness = 1.1 -> 0.7
rudder_effectiveness = 1.3 -> 1.1

In the couple of fair weather flight I have flown I have found this combination has eliminated the pitch oscillations in level flight. Also, VNAV descents now work smoothly. VNAV ascents have been improved significantly however there is still an issue with the first 30 seconds or so. In VNAV ascent the rate of climb initially rises slightly but then quickly swings into a negative rate, then followed by oscillations between positive/negative rate which gradually stabilize within 30-45 seconds. (Without the above mods those oscillations would never stabilize.)

I will be doing more testing on all this later today.

Using P3Dv1 and the SimA 737.

Fred K
Spent the entire afternoon investigating further tuning doing flight level changes......

In addition to the above I have changed the following in the SimA A/P tuning section:

[FLCH]

Accel Damping: 0.7 -> 0.1
Sensitivity Reduction: 6 -> 9
Desc Aggression: 5 -> 3

All of the changes I have made are in the direction of decreasing sensitivities and increasing damping. I systematically titrated to each of those values.

The results are that the oscillations are completely eliminated in level flight and the FLTCHG performance is very smooth and acceptable (both VNAV and LVL), albeit perhaps a little bit slow to initiate, but I can live with that.

If this sticks I am happy.

Fred K

pilotito84
Posts: 52
Joined: Mon Sep 11, 2017 3:47 pm
Location: Tucson, AZ

Post by pilotito84 »

Thank you all for jumping into this thread and taking the time trying to help me figure it out. So far, I have also reduced the weather to zero and everything was fine up to the level off, it then just started doing its thing again. Also still no luck with the out of turn coordination issue as well.

Thank yo for the welcoming message MichaelYSSY :D

kand
Posts: 214
Joined: Wed Feb 03, 2016 3:48 pm
Location: Buckinghamshire, UK

Post by kand »

Tankleader wrote:
MichaelYSSY wrote:Hi guys



Not getting this problem with 1.91 but it did happen with a previous SA version 1.8?


Cheers
Michael
Where is everyone getting 1.91 from? I just downloaded 1.9 from the link on the announcement page.

Thanks
Andy
On the download page of the simA website, 1.91 latest official release

Tankleader
Posts: 33
Joined: Fri Dec 23, 2016 8:12 am

Post by Tankleader »

kand wrote:
On the download page of the simA website, 1.91 latest official release
Thanks, I didn't think to check there.

Thanks
Andy

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