Servo impotent?

[skyboy999]

My system seems to have lost the ability to maintain track. No settings have been changed, no fault is reported and it is not sheared. Real time monitoring is active so it must be getting power and thinks it is operating ok. Also, it is easy'ish to overpower and no 'Slip" message appears when this is attempted.

It looks to me like the servo (A32) must be at fault but feedback welcomed, especially any suggestions for more diagnosis.

If it is at fault, is it user serviceable?

Thanks

 

[Marc_J._Zeitlin]

My system seems to have lost the ability to maintain track. No settings have been changed, no fault is reported and it is not sheared.... Also, it is easy'ish to overpower and no 'Slip" message appears when this is attempted.

Those symptoms certainly sounds like a broken shear screw - what makes you think that it's NOT sheared?

And except for a broken shear screw, there are no user serviceable parts in the servo.

 

[skyboy999]

Those symptoms certainly sounds like a broken shear screw - what makes you think that it's NOT sheared?

And except for a broken shear screw, there are no user serviceable parts in the servo.

The servo arm moves with stick. I thought, if sheared, it would be loose? Also, I thought there would be a fault reported?
If this not correct, is there a way I can check?

 

[airguy]

If it's sheared, it may well move with the stick until/unless force is applied to the control surfaces, resulting in torque at the shaft which the shear screw normally resists. Try turning on the autopilot (sitting on the ground) in "level" mode and try to move the control surfaces yourself - or have a helper hold the control surfaces while you tell the AP to climb/descend and turn. Put the screen into servo test mode and you can see the positions of the servo and the force feedback on the servo - if the position is changing on the screen, but the control surface movement is not firmly slaved to that position, you have a shear screw broken. The AP will not report "slip" in this case because it thinks the servo is moving (changing position) even though the force is not being passed onto the control column.

 

[skyboy999]

If it's sheared, it may well move with the stick until/unless force is applied to the control surfaces, resulting in torque at the shaft which the shear screw normally resists. Try turning on the autopilot (sitting on the ground) in "level" mode and try to move the control surfaces yourself - or have a helper hold the control surfaces while you tell the AP to climb/descend and turn. Put the screen into servo test mode and you can see the positions of the servo and the force feedback on the servo - if the position is changing on the screen, but the control surface movement is not firmly slaved to that position, you have a shear screw broken. The AP will not report "slip" in this case because it thinks the servo is moving (changing position) even though the force is not being passed onto the control column.

Thanks. Very helpful and, as you say, confirms culprit is sheared screw which I will replace.