Stick chatter

[Phil B]

Sometimes while on final my control stick chatters as I move it left and right.  It's very disconcerting almost as it something is binding it.  Any ideas?

[Tom Baker]

Are you feeling the AP servo, or something else?

[Phil B]

I don't know.  The aircraft is new to me and now that you mention it, it could be me fighting the A/P.  It is a scary, like there is something wrong with the linkage.  How can I tell if that's the issue?

[Runtoeat]

Do you get this if the A/P is "off"?  Do you have a CTSW or CTLS and what year?  One quick thought.  I know of an instance where the plexi-glass shield that goes around the BRS parachute was pushed into the aileron linkage by baggage and would "catch" on the linkage.  This was on a CTLS.

[Phil B]

I'm a 2008 CTLS.  I looked in the baggage area which is empty and did not see any deformity in the Plexiglas protecting the linkage.  I don't know if the a/p was off, I didn't look at the time.  If, when this happens I pull the a/p breaker, will that kill all power to the servos also?

[coppercity]

3 hours ago, Phil B said:

Sometimes while on final my control stick chatters as I move it left and right.  It's very disconcerting almost as it something is binding it.  Any ideas?

I have had students press the AP button on the control stick accidentally while trying to make a radio call instead of the push to talk, this button turns the AP on as well as off.   

[coppercity]

2 minutes ago, Phil B said:

I'm a 2008 CTLS.  I looked in the baggage area which is empty and did not see any deformity in the Plexiglas protecting the linkage.  I don't know if the a/p was off, I didn't look at the time.  If, when this happens I pull the a/p breaker, will that kill all power to the servos also?

Yes, pulling the breaker will disable servos and control head.

[FlyingMonkey]

I would definitely want to get this sorted out.  If it's not the AP it sounds like a potentially dangerous condition.  It seems to me that if you were fighting the AP on final you'd eventually break a servo shear pin and the resistance would stop...

[Tom Baker]

As Eric said you can turn on the AP by pushing the AP disconnect button, but you have to hold it down for few seconds for the AP to engage.

When you say chatters is it a big chatter or a small chatter. With the AP on it will make a pretty big bump. with it off you can still feel the notches in the stepper motor. Also any other binding in the control system could cause a chatter feel in the stick.

[Tom Baker]

34 minutes ago, FlyingMonkey said:

I would definitely want to get this sorted out.  If it's not the AP it sounds like a potentially dangerous condition.  It seems to me that if you were fighting the AP on final you'd eventually break a servo shear pin and the resistance would stop...

It depends on the torque setting on the servo. It may just continually jump to the next step in the motor instead of sheering the pin. 

[Runtoeat]

I'm thinking you did as Eric suggests which is pressed the AP "on" button without realizing it - or pressed it instead of the radio talk button.  This will put the AP into "altitude hold".  When you try to move the stick with the AP in this mode, you will get significant "chatter" from the stick because the pitch and roll servos are resisting any bank or pitch change you are trying to make.  If the "torque" is set to a high value, the "chatter" is significant.  The only other thing I will mention is I experienced aileron "lock up" due to the torque mulitplier coming apart on the roll servo and jamming my ailerons.  My older TruTrak system had a torque multiplier that was defective and had to be replaced.  I don't believe your 2008 would be affected by this.

[Anticept]

I had to replace an autopilot servo torque multiplier (the device that has a wheel, steel rope, and a attachment assembly). The steel rope partially broke  and was tying up the wheel. Itould bind up the roll control very stiff. With the AP off, I could still feel it bind. It was located in the cargo compartment. It was on a 2010 CTLS

[Runtoeat]

Corey, same as me.  Having my aileron control partially lock up was not a good experience.  In my case, the servo's cable anchor pin pulled out of the phenolic wheel.  This did not result in "chatter" but was a constant drag when trying to bank.

[FlyingMonkey]

On 4/22/2018 at 8:01 AM, Runtoeat said:

Corey, same as me.  Having my aileron control partially lock up was not a good experience.  In my case, the servo's cable anchor pin pulled out of the phenolic wheel.  This did not result in "chatter" but was a constant drag when trying to bank.

Adding this to my periodic inspections!