Jesse Lin in Avionics Bench
2004 Cirrus SR20, autopilot disconnects in moderate turbulence but only in altitude hold, never in heading mode. Shop says it is the servo. That does not match the symptom to me but I fix software for a living, not airplanes. Am I wrong?
you are probably not wrong. altitude hold only points at the pitch side, so pitch servo, pitch trim, or the static system feeding the altitude reference. ask them what they actually tested vs what they inferred
The word "says" is doing a lot of work in that quote. Get the troubleshooting steps in writing before you approve a servo.
Asked. They tested nothing, they replaced a servo on a different airplane with a similar complaint once. Getting a second opinion.