Citation II S2/Bravo (C550)
Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 135; Flight Crew Total 8500; Flight Crew Type 1275
Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Loss Of Aircraft Control
Aircraft Aircraft Damaged; General Maintenance Action
Aircraft; Human Factors
We departed early AM for the flight to CID. The flight progressed normally with me acting as the non pilot flying (NPF)SIC.  20 minutes away from the airport I began checking the weather at CID and performing the Descent; Approach; and pre-landing checklists. The first time I checked the weather it was reporting 1 sm and 200 BKN so I listened to the weather 2 more times before the approach. The last time that I checked the weather we were on downwind leg being vectored for the approach and Cedar Rapids was reporting 1/2 mile visibility and 200 Broken on the automated report. Chicago center vectored us for the ILS runway 9 approach. We executed the approach as normal and configured the airplane prior to the final approach fix for runway 9. The normal callouts of 1000 to DA (Decision Altitude); 500 to DA; 200 to DA; and 100 to DA were made by me as the NPF. Just after the 100 to DA callout was made I had the Approach Light System (ALS) in sight then the runway in sight. I identified the runway in sight to the pilot flying (PF) Pilot in Command (PIC) at which time he identified it and continued visually. I felt that the PIC had disconnected the autopilot and yaw dampener because the aircraft began a normal flare to landing maneuver. My attention was directed outside the aircraft at the landing runway and there was no aural identification that the autopilot disconnected. During the flare the aircraft made an abrupt right turn which the PF reacted to and returned the aircraft to centerline. The landing was normal other than the abrupt turn to the right. After touchdown the PIC made a comment that the Yaw dampener was still connected. We proceeded off the runway where normal after landing checklists were completed and taxied to the ramp without incident. I believe that the autopilot was still connected and the PF was fighting it when the aircraft made the abrupt turn.Once at the ramp the aircraft was shut down and I opened the cabin door when the ground personnel notified us that there was a hole in the left hand flap trailing edge. The hole was just aft of the landing gear and there was no other damage noticed.Corrective actions:1) Some type of visual indication to the right seat pilot to identify when the autopilot is disconnected within his field of vision.2) An aural alert to the crew when autopilot is disconnected.3) Adherence to company procedures when and how the autopilot should be turned off.
I was enroute on a re-position flight to IOW and diverted to CID due to rapidly deteriorated weather. Vectored to ILS 9 at CID flew ILS coupled approach checklist completed prior to beginning coupled approach and before landing completed prior to DH. Approach was normal and runway end lights were obtained just prior to DH. At the flare and touchdown later the aircraft made a pronounced deviation to the right and it was determined later that the extended flaps had impacted a runway light. I had sufficient flying speed to return the aircraft airborne and slip it back to the middle of the runway. The aircraft was then brought to a normal stop and exited the runway to the ramp. I noticed during the after landing check the autopilot/yaw damp engage lights were still illuminated and the pitch trim was in the max nose down position. Apparently when I triggered the 'disconnect' button on the control wheel it either didn't disconnect or re-engage during the descent to the runway. Since we had done a coupled approach down to the DH the autopilot apparently tried to keep the aircraft descending as we flared for the landing and the yaw damper was contradicting the rudder inputs I was making to align the aircraft with the runway. This definitely affected control of the aircraft.
C550 flight crew describes an ILS approach to minimums; then landing apparently with the autopilot/yaw damper engaged. During the flare an abrupt right turn occurs which the  pilot flying corrects back to the center line. Post flight reveals a hole in the left flap behind the landing gear.