( @Bert Pieke will be interested in this one!).

One thing I'd noticed in almost all aircraft in MSFS is the jerkiness and initial instability, when engaging the AP.

I went down a rabbit hole today and discovered two hugely important new variables that are available (but as yet almost wholly unused) in the [AUTOPILOT] section of the systems.cfg files, for each aircraft.

These new variables are:-

pitch_pid_reset_mode=2
roll_pid_reset_mode=2

A value of '0' relates to a Dirty or 'last known' engagement - this is the default value.  When set, the last known positions of the servos will be restored. (A bit like 'resume' on your car's cruise control).  So if you last disengaged the AP with any large deflections, the servos will quickly just to those deflections when the AP is engaged. This results in an abrupt engagement.

The value '1' relates to a 'neutral' engagement.  What that means is that, at the point the AP is engaged, the servos will all be at their neutral positions, and will need to momentarily set themselves to the flight control deflections of when the AP was engaged. This also results in an abrupt engagement as when the AP is engaged, the servos move to neutral positions, and then need to move to the current deflections.

The holy grail value is '2', which relates to a 'clean' or matched engagement, where the initial servo positions will be exactly where the flight controls are currently deflected, when the AP is engaged.  This setting is how almost all AP's behave when engaged.

However, unless the above two values are added to the [AUTOPILOT] section of the systems.cfg you will always get the undesired 'dirty' engagement, and the initial jerkiness, as this variable is not (yet) included in default aircraft's systems.cfg, and the default value of operation is '0'.

I did an 'audit' of all aircraft that I currently have installed in MSFS, and the only aircraft that were currently using the above variables (and set to '2') were the WBSim C172 (Classic) enhancement Pack and the (freeware) C172 G1000 Enhanncement Pack from Bagolu (on Flightsim.to).

So..... if you want smooth, realistically engaging APs in your aircraft, simply browse to the systems.cfg file, within each aircraft's directory, scroll down to the [AUTOPILOT] section, and add the above two lines to the bottom of the autopilot section, before saving and exiting.

I tested this with the stock VL3 as that plane always jerks badly when the AP is engaged - with the above lines added, the AP engages as smooth as butter!

Edited December 11, 20223 yr by JYW

That is most certainly interesting.. 😉

If this works, you deserve some compensation from MS and the rest of the Dev's who never figured that one out.. 👍👍

1 hour ago, Bert Pieke said:

That is most certainly interesting.. 😉

Get testing Bert 😎  A before and after reveals how striking the difference is.

30 minutes ago, Pivot said:

If this works, you deserve some compensation from MS and the rest of the Dev's who never figured that one out.. 👍👍

It is certainly odd that the SDK states that a value of '2' is "recommended", but that a value of "0" is the default value!  Perhaps they regard these new variables as still "in testing".

Edited December 11, 20223 yr by JYW

I will try this but I also think a factor is how trimmed the aircraft is prior to AP engagement.  Most people just engage AP with the plane all out of whack and it reacts aggressively usually.

4 minutes ago, JYW said:

Get testing Bert 😎  A before and after reveals how striking the difference is.

Just tried this with the FSW C414. My initial testing is encouraging.

Thanks,

Al

 

1 hour ago, JYW said:

Get testing Bert 😎  A before and after reveals how striking the difference is.

Hmm, not all airplanes have this file accessible.. the Carenado PC12 has it "hidden"..  Will try some others and report back.

Edit: Just tried the RV14, and it feels nice!

Edited December 11, 20223 yr by Bert Pieke

35 minutes ago, ryanbatc said:

I will try this but I also think a factor is how trimmed the aircraft is prior to AP engagement. 

Agree, the plane has to be in trim. Would not make sense to have the AP initially lock onto an out of trim setting.

Al

Edited December 11, 20223 yr by ark

I just checked the Updated Milviz/BB 310 and the systems.cfg did not include those parameters. I did, however, have a Default VS Climb rate that showed a value of "=0" and Commented out //Previously =700. I reset this to "700" and will give it a try, since it did the Level off the minute of engagement when I was trimmed for an 800' climb rate. 

I think it was the Kodiak that had pitch change issues when turning off the AP on an approach. Wonder if this will help with that, or has the problem already been solved?

Al

EDIT: Ignore the above. As Bert points out below, this is a potential fix for when the AP is Engaged, not Disengaged.  🙁

 

 

Edited December 11, 20223 yr by ark

8 minutes ago, ark said:

I think it was the Kodiak that had pitch change issues when turning off the AP on an approach. Wonder if this will help with that, or has the problem already been solved?

Al

Turning "off" the autopilot may not be covered here.. 😉

I can't say that I've had any "twitchiness" with the engagement of the AP on any aircraft - usually pretty smooth.

I'm waiting for an update on the Kodiak before I fly her again - if I have any issues after that, I may try your tweak.

Added to the 414, which I find does have an agressive pitch down when you engage IAS mode. I will report back!

2 hours ago, Bert Pieke said:

the Carenado PC12 has it "hidden".. 

While MS/Asobo has unlocked default aircraft my understanding is they did not likewise unlock payware models purchased through the MS Store.