Pitch Oscillations and Uncoordinated flight

[Tankleader]

Pitch Oscillation Issue
The following occurred while trying to level off at programmed cruise altitude FL360.

The AP, LNAV, VNAV and A/T where armed with CLB indicated on the EICAS. There was a slight change in the wind direction and the altitude started to slowly porpoise in increasing pitch with a corresponding increase or decrease in speed. The FMC/CDU was displaying BUFFET ALERT message.

I disconnected the autopilot and used the YOKE to slowly decrease the porpoise effect. Once stabilized I reengaged the AP and everything stabilized.

I checked the Server FLT Data Rate = 15 FPS and A/P Rate = 10 FPS. In my earlier post I thought this could be the cause. I checked my FSUIPC and Wide Server.ini files and they are all pointing to the correct IP’s All IP’s are static.

I am still flying and connected so I know WIDE FS did not disconnect.
Sim Avionics Version = 1.91
FSUIPC Version= 4.974
WIDEFS Version= 7.151
Aircraft Version= 1.9 (777)
Active Sky Settings are default with Enhanced Turbulence set to OFF
Turbulence Settings in P3Dv3.4 are off as well.

I did another flight and just as I was approaching the Altitude set on the MCP the aircraft started to oscillate, I disconnected the AP and manually tried to null out the oscillation but was unable to.

I then set a higher altitude on the MCP and the aircraft climbed to and captured the altitude without an issue.


Throttle Issue
I am having an intermittent throttle issue while trying to taxi, the EICAS shows my throttle input but no response from the engine. If I engage and disengage the reversers my engines, then start responding to my inputs.

Thanks
Andy

[Rigilkent]

Tried a couple of flights today and experienced very similar issues to what Andy is describing: oscillations when trying to capture and maintain MCP altitude in VNAV mode.

However, I was able to stabilize it without having to disconnect the AP, but simply switch from VNAV to ALT HOLD. Once the altitude was captured, I reengaged VNAV and everything was stable.

From that point on (again similar to Andy)when setting a higher altitude VNAV performed as expected, climbing and capturing the new altitude no problem.

Iam using the version 1.9 (have not upgraded to 1.91) and have P3dV4.3 so using FSUIPC v5.
Aircraft is the 777 v 1.9.
All A/P values are default one per recalling them after having upgraded to v 1.9.
I cleared all weather so I did not experience any wind shift as a potential trigger to the porpoising.
So I wonder if it is a VNAV problem?
Will keep testing as well....

Andrea

[kondrat]

Hi Andy,

Regarding Throttle Issues you mentioned.

Try to change N1 target in server configuration panel:

Aircraft detail-> Engine details-> N1 target-> 21

Regarding oscillations see another recent post about the same problem. I changed the recommended values and everything smooth.

Denis

Pitch Oscillation Issue
The following occurred while trying to level off at programmed cruise altitude FL360.

The AP, LNAV, VNAV and A/T where armed with CLB indicated on the EICAS. There was a slight change in the wind direction and the altitude started to slowly porpoise in increasing pitch with a corresponding increase or decrease in speed. The FMC/CDU was displaying BUFFET ALERT message.

I disconnected the autopilot and used the YOKE to slowly decrease the porpoise effect. Once stabilized I reengaged the AP and everything stabilized.

I checked the Server FLT Data Rate = 15 FPS and A/P Rate = 10 FPS. In my earlier post I thought this could be the cause. I checked my FSUIPC and Wide Server.ini files and they are all pointing to the correct IP’s All IP’s are static.

I am still flying and connected so I know WIDE FS did not disconnect.
Sim Avionics Version = 1.91
FSUIPC Version= 4.974
WIDEFS Version= 7.151
Aircraft Version= 1.9 (777)
Active Sky Settings are default with Enhanced Turbulence set to OFF
Turbulence Settings in P3Dv3.4 are off as well.

I did another flight and just as I was approaching the Altitude set on the MCP the aircraft started to oscillate, I disconnected the AP and manually tried to null out the oscillation but was unable to.

I then set a higher altitude on the MCP and the aircraft climbed to and captured the altitude without an issue.


Throttle Issue
I am having an intermittent throttle issue while trying to taxi, the EICAS shows my throttle input but no response from the engine. If I engage and disengage the reversers my engines, then start responding to my inputs.

Thanks
Andy

[Fred]

Likewise.....Do try the mods I posted in this thread above for the SimA A/P Tuning section [FLTCHG]. Did several flights this weekend.....all were absolutely smooth including VNAV function.

(Note: The mods I made to the aircraft.cfg file can be ignored...not necessary I have found.)

Fred K

[Tankleader]

Likewise.....Do try the mods I posted in this thread above for the SimA A/P Tuning section [FLTCHG]. Did several flights this weekend.....all were absolutely smooth including VNAV function.

(Note: The mods I made to the aircraft.cfg file can be ignored...not necessary I have found.)

Fred K

What about the Alt Hold Accel Damp -700 > -1200.

Thanks
Andy

[Fred]

Likewise.....Do try the mods I posted in this thread above for the SimA A/P Tuning section [FLTCHG]. Did several flights this weekend.....all were absolutely smooth including VNAV function.

(Note: The mods I made to the aircraft.cfg file can be ignored...not necessary I have found.)

Fred K

What about the Alt Hold Accel Damp -700 > -1200.

Thanks
Andy

Yes...I am using that as well.

To be clear:

In SimA A/P Tuning:

[ALT HOLD]
Accel Damping: -700 -> -1200

[FLCH]
Accel Damping: 0.7 -> 0.3
Sensitivity Reduction: 6 -> 8
Desc Aggression: 5 -> 3

Those values are slightly refined from my original, and you do not need to make any changes in the aircraft.cfg.

I did quite a bit of flight testing over the weekend since I am preparing to host a WorldFlight team here. With 1.91 I went from uncontrollable oscillations in level flight and ascents/descents to essentially perfect smoothness for both....the best performance I have ever had with SimA in fact.

Fred K

[jackpilot]

FRed

This is for the 737 I suppose...?

[Fred]

Yes...This is for the 737.

Also.....I did some further work today to better sync airspeed hold on altitude changes. The issue is that the increased thrust that occurs for an ascent causes the IAS to rise as much as 5-10 knots over target before the vertical speed rate catches up and takes over, at which time the IAS settles back to target. This was a minor issue before I started making the oscillation changes but was exacerbated I think with the increased damping and dumbing down of the sensitivities for the [FLCH] section etc.

Those changes are:

[Airspeed Hold]

Sensitivity Reduction: 1.1 -> 1.3
Damping: 1.1 -> 1.6

It is all working very nicely though!

Fred K

[Tankleader]

Pitch Oscillation Issue:
Based on the work of Fred I have brought the pitch oscillation under control. See my settings below.
Denis, thanks for your suggestion on the throttle, it now works as it did prior before.

I am still having an issue with the throttle/overspeed while leveling off at the designated flight level with A/T engaged.

Sim Avionics Version = 1.91
FSUIPC Version= 4.974
WIDEFS Version= 7.151
Aircraft Version= 1.9 (777)
A/P Detail Settings
Airspeed Hold:
Sensitivity Reduction 1.1 - 1.3
Damping 1.1 - 1.6

FLCH:
Sensitivity Reduction 3 – 5
Acceleration Damping .6 - .4
Desc Aggression 5 – 3

Airspeed Hold:
Sensitivity Reduction 1.1 – 1.3
Damping 1.1 – 1.6

Aircraft Engine
N1 Target 21.6 – 21


Thanks
Andy

[737SimGuy]

ALWAYS when upgrading to a new Sim-A version be sure to Recall Default Autopilot Values. This is found on the Autopilot + Recalls tab. Remember to SAVE this to your aircraft config file as instructed in the dialog popups. This ensures you have Marks latest, possibly updated, settings.

James

[ddoyle]

Hi Everyone

I had this issue too. After a few tests i still had the issue. I then decided no to have my ATC addon (ProAtcX) running.

After testing it seemed that the issue was gone. So this is what was causing my issue. But i as stated in the previous post. I always recall autopilot, engine and flaps defaults. After every update as per Mark's instructions.

Regards

[Fred]

Hi Everyone

I had this issue too. After a few tests i still had the issue. I then decided no to have my ATC addon (ProAtcX) running.

After testing it seemed that the issue was gone. So this is what was causing my issue. But i as stated in the previous post. I always recall autopilot, engine and flaps defaults. After every update as per Mark's instructions.

Regards

I believe this is network traffic related and 1.91 seems to be a bit more sensitive. I have observed that if I start removing network related components.....like VATSIM ATC or FSGRW Weather or a USB controller connection or even if I disconnect Navigraph running on my IPad the avionics performance tends to improve. However the SimA network traffic stats on the server never seem to deviate.

It is interesting that adjustments in the SimA A/P settings etc. as I have suggested earlier in this thread do seem to help to calm it all. However for the time being I have moved back to using 1.85 which seems to be much more stable and immune to being affected by other network connections.

Fred K

[VE3ORE]

A few months ago I changed one of my network switches to one that would support VLAN,s . I have my SimA server and my P3D server setup on a dedicated VLAN. You can get inexpensive switches that support this now. I believe this may have helped me avoid some of these issues. I will post details of the switch if anyone is interested..

Andy

[Jetcos]

Hi Andy,

Please post for us. Sounds interesting.

Thanks!

[VE3ORE]

The switch I am using is a 5 port unit from TP-Link. The model is TL-SG105E. I think it has to be the E version to support VLAN’s. I am using the port based VLAN setup to include my SimA server and my P3D machine. This is a very basic switch and cost about $50 Canadian. I am sure there are better switches available but it seems to work for me.

I have several other servers and dumb switches in my network, TV’s etc. Direct traffic on the VLAN between SimA and P3D is isolated however both computers can communicate normally to the rest of the network and internet etc. which is needed for weather updates, access to flight planning desktop etc.