Flight Crew Air Transport Pilot (ATP)
Distraction; Troubleshooting; Workload
Inflight Event / Encounter Unstabilized Approach
Flight Crew FLC Overrode Automation
ATC Equipment / Nav Facility / Buildings; Airport
During the approach and landing phase at CKB both myself as the PM and the PF noticed the autopilot having a difficult time tracking the ILS on RWY 21. The winds were not a factor considering they were steady state with little to no crosswind the cloud layer was 1000 OVC. We allowed the autopilot to try to stabilize on the ILS while we were outside the FAF; allowing the autopilot to command several s-turns to either side of the inbound course while it tried [to] chase the LOC course dot; which was deflecting a dot either side of desired track. The PF decided to disconnect the autopilot and hand fly the approach using the raw data on the ND in Arch mode and the approach was continued in a stabilized manner using this mode. The FD; LOC and GS; on the PFD continued to show erratic tendencies as the LOC/GS deviation displays. As the PM I was keeping close attention to the terrain on my ND and watching visually outside with 75% visual of the terrain. I noticed the FD continued to command corrections trying to chase the erratic LOC/GS deviations; including a pitch down while over the high terrain bluff on about a mile final; a potential dangerous situation if flown with a coupled approach down to minimums. While talking to the agents in the airport they confirm they had heard other pilots talking about irregular behavior with the ILS 21. We departed CKB and flew a coupled ILS 9L there and noticed no irregular behavior with the aircraft; which furthers my thought that there may be something wrong with the CKB ILS 21 Navaid/Approach. Have the ILS flight checked to see potential sensitivity and interference problems. Possibly request other feedback from pilots flying the approach into CKB. Possible memo to pilots on the potential for irregular tracking of the ILS using automation.
Air carrier Captain reported receiving erratic signals from the CKB Runway 21 ILS while on approach in IMC. The crew disconnected the autopilot and the approach was completed uneventfully. Ground personnel mentioned to the Captain that several pilots referenced the irregular quality of the ILS signal at CKB.