Date: 202108
Local time of day: 0601-1200
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ZZZ
Aircraft component: Autopilot
Component problem: Malfunctioning; Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Distraction; Physiological - Other; Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Maintenance
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: Conducting Captain OE...reviewing logbook I notice MX (Maintenance) had a few issues with the Captain AP (Autopilot)/trim DISC placard.  Night prior ZZZ MX had applied a placard; ops check good. I think nothing of it; I'm in the right seat; we move along. Going into ZZZ1; ILS to XX; Captain OE; leg one; properly briefs autopilot coupled approach not approved; so I will disconnect the autopilot at the FAF. Approaching FAF he says gear down; flaps 3; we were doing 180.He clicks off the autopilot; his button is stuck in; which results in the aural 'autopilot; autopilot' to continue.  He asks me; can you cancel on your side?  I hit my button a couple times and say no I can't cause your button is stuck in.  He struggles trying to get his button to release; I tell him; fly the airplane; push the nose over; fly the airplane. He says; I can't get the button out; I say whatever; fly the airplane. We are going to hear this alert the whole way down; while annoying; whatever; block that out and fly the airplane. He pushes the nose over and flies the ILS. I see an AP FAIL caution; but there is no aural alert cause the continuous 'autopilot; autopilot' takes precedence.  I call out AP FAIL; disregard and continue; just fly the airplane.This is first leg of Captain OE; so he is left of centerline; but decent touchdown; then the nose slams down.  He says I had no trim; I say whatever; get on the brakes. We pull off the runway; with aural alert 'autopilot; autopilot' still going off.  We work our way to the ramp through ground and ramp frequency with this alert still yelling at us.We shut down; alert still going off; I reach over to his disconnect button; dig my fingernails into it and get it to come out enough to stop the alert.So; at the FAF we had the autopilot/trim disconnect button stick in. This caused the autopilot alert to continue; but more importantly continued to give a trim cutout signal; which meant our pitch trim was inoperative. The trim was set for flaps 3; gear down; speed 180...it was at 2.5. This meant he had to muscle the elevator to overcome the trim; pulling back excessive forces to maintain glideslope all the way down to touchdown. When I dug the button out I immediately saw the problem. The night prior; ZZZ MX had corrected an AP/Trim DISC placard write up. It appears they applied some homemade placard with a whole ton of adhesive. This adhesive caused the button to stick in (engaged) sending a trim disconnect signal; when it was pressed.ZZZ1 MX dug all the adhesive out with a dental looking pick; applied a proper placard with a couple drops of glue; and we were good to go.My FO (First Officer) (IOE) last week told they had a problem; on his previous trip; disconnecting the autopilot due to excessive glue on a 'homemade' placard.I would like someone to tell the mechanic...here is the problem you caused with your excessive adhesive on some rinky-dink placard you guys manufactured.




Synopsis: Air carrier Captain reported that on approach; the First Officer's AP (Autopilot) button became stuck when attempting to disconnect the AP. The button could not be unstuck; which resulted in inoperative pitch trim and continuous AP aural alert during the approach. The First Officer was able to overcome control forces to land the aircraft. Post-flight it was learned that maintenance had applied a placard with adhesive which had caused the AP button to stick.