Auto throttle hunting

[blueskydriver]

Hi Gerard,

I'm sorry I didn't get a chance too help you. Karen and I have been so caught up in dealing with issues concerning our new shed/hangar that I haven't had the time to turn my simulator on and check things for you. Not sure when I'll get too it...

John

[bravolima]

I want to share my experience. My pm-setting as well shows throttle hunting. If I disable all weather injection, the system works perfect and keeps the speeds flawless...
Even if I use weather from the pm-instructorstation speedhunting occures. Usually I use FSGlobalWeather in a network setting.
My next step is a trial series with several airmodels. ProSim model I will give a try as well, but the model has to be adapted and I´m not sure about it.
I will keep you informed about the results. I´m interested if anyone could confirm the weather relation to speed hunting.
At the moment I use a the pm 737 flightmodel with some minor modifications.

Bernhard

[GSalden]

Bernard,

If you are interested give me a pm with your email adres and I will sent you a dl link for my flightmodel.

I have made a Topic at the Fsuipc forum and asked for help for a LUA script which slows down the flying speed by 10 knots when under 11000 ft.
Eg : now mcp speed is 135 --> flying speed is 145-150

However Pete is on holidays till next week, so it might take some time.

Also later I want to take a better look at the throttle hunting issue.
I was thinking about a delay feature. Now they go up and within 2 seconds they come down.
If there is a delay of 2 seconds they won't go up that high and act more stable.


Regarding your findings with the throttle hunting :

When using certain high-fidelity aircraft including PMDG 747, MD-11 or other high-sensitivity aircraft, turbulence effects can result in stability problems and potential s-turn autopilot hunting. Both FSUIPC turbulence effects and FSX internal turbulence effects (used by AS and FSX itself) can cause these problems. In order to minimize these harmful effects, it is recommended to minimize/disable turbulence effects in both FSUIPC (if in use) and FSX.


FSUIPC (if installed and FSUIPC wind smoothing/turbulence effects are enabled) - Edit These FSUIPC.ini settings:
TurbulenceRate=0.5,2.5
TurbulenceDivisor=40,40,80,80

FSX - Edit the following FSX.cfg setting (under [Weather]):
TurbulenceScale=0.500000

[bravolima]

Thanks for the hints regarding turbulenceRate. I will give them a try. My proposal to sort things out is to start with essential settings, perhaps configure a testbed on a second system. When disturbing factors identified, then they might be eliminated.

thanks & regards

Bernhard

[willow]

Greetings

I have had this issue for several months.  A/T is perfect when weather is turned off, but as soon as weather injection occurs the A/T begins to hunt - especially in turns and descents.  I am using ProSim737 flight model with Opus FSI weather.  I have attempted a work-around by turning off GRIB data in OpusFSI, as well as other variables in Opus and FSUIPC but the issue still persists.

I spoke with Stephen at Opus about this issue and it appears the problem is (maybe) an underlying fault in FSX.

I have trialed the Salden's suggestion in addition to advice provided on another forum which suggested to alter the max_throttle_rate.

I am using the ProSim V2 flight model and have made a post on their forum:  http://www.prosim-ar.com/forum/viewtopic.php?f=23&t=9069&sid=1a6ab1ed018250b3c705f7865c3d4e88&p=66629#p66629

Cheers,  WilloW

[Bob Reed]

Well after several tests, it is not just weather related, at least no my issue. With live weather (Activsky Next) on it is much more pronounced. 5 flights tonight and never turning on weather, the AT and speed stayed out of whack. Speed stayed several KTS's over commanded. Now with weather off the "S" turns on approach went away. This is Project magenta with PM MCP turned to "off". More tests to follow...

[willow]

Thanks for the note Bob

The thread over at ProSim has a detailed post on the issue

http://www.prosim-ar.com/forum/viewtopic.php?f=23&t=9069&sid=1a6ab1ed018250b3c705f7865c3d4e88&p=66629#p66629

Cheers,   WilloW

[GSalden]

If the PM mcp is turned off than the default 737 mcp will be used.

[Trevor Hale]

Just found this...  Go to the [autopilot] section of your aircraft.cfg file and locate max_throttle_rate. if it isn't there add it.  This value is always set to 0.10 by default.  Start by cutting this value in half to 0.05 or less.

max_throttle_rate

This value sets the maximum rate at which the autothrottle will move the throttle position. In the example, the maximum rate is set to 10% of the total throttle range Douglas DC-3( max_throttle_rate=0.100000 )

This should fix your issue. you will have to find the "Happy medium" Too slow and your throttle will never catch up.  Too fast and it will always blow past the setpoint.

Trev

[willow]

Just found this...  Go to the [autopilot] section of your aircraft.cfg file and locate max_throttle_rate. if it isn't there add it.  This value is always set to 0.10 by default.  Start by cutting this value in half to 0.05 or less.

max_throttle_rate

This value sets the maximum rate at which the autothrottle will move the throttle position. In the example, the maximum rate is set to 10% of the total throttle range Douglas DC-3( max_throttle_rate=0.100000 )

This should fix your issue. you will have to find the "Happy medium" Too slow and your throttle will never catch up.  Too fast and it will always blow past the setpoint.

Trev

This problem actually rectified itself on my system after a few version updates from ProSim-AR.   Still the information is good to know should the issue occur again.   Cheers,   WilloW