Flight Crew Air Transport Pilot (ATP)
Workload; Distraction; Training / Qualification
Aircraft Equipment Problem Critical; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Took Evasive Action; Flight Crew Returned To Clearance
Aircraft; Company Policy
While on our base turn to intercept the localizer both Pilot Flying and Pilot Not Flying switched from white needles to green needles with the final approach course set to 190 degrees. On the final vector turn (heading 160 degrees) the approach mode was armed. The autopilot captured the localizer and initiated an erroneous left turn to a heading of approximately 110 degrees before I noticed it and instructed the Pilot Flying to select heading mode and turn the aircraft manually to a heading of 210 to re-intercept the localizer. At this time I checked to see that we were not in conflict with an aircraft on the parallel approach and luckily they were below us by about 1;500 FT. Approach Control asked if we had the localizer captured and I stated we had an autopilot issue but were established on the course inbound. CRJ pilots received a memo about this issue with the autopilot system. It will occasionally capture and aggressively attempt [to] align the aircraft with the inbound course; sometimes outside the maneuvering capabilities of the aircraft. The manufacturer has no fix for this issue so the solution is to capture the inbound course using white needles and then switch to green needles. Lately; during yearly proficiency training; pilots; including myself and the Pilot Flying have been told to capture using green needles which contradicts the memo. While I understand capturing using green needles works 100% of the time in the simulator it does not in the real world. In the future I will follow the guidance of the memo and hope the manufacturer is able to come up with a fix for this potentially lethal issue in the future.
The reporter stated a Company bulletin describes the issue experienced by this crew and adds that the same event can occur during or prior to glideslope capture. In fact; several years ago the reporter's aircraft did attempt to abruptly fly up to the glideslope before the glideslope was active and captured. The current procedure at his Company is contrary to the published procedure in that the crews are to capture in White Needles (VOR/LOC); let the aircraft stabilize then select Green Needles. The reporter is concerned about parallel and PRM approaches in the future. He has noticed in his years as a Captain that ATC is spacing aircraft more closely; and in this specific event the margin of safety was maintained by the altitude separation.
A CRJ-700 in Green Needles with the Approach Mode Armed turned away from the localizer final approach course after LOC CAP so the crew selected heading mode and returned to the localizer. The particular aircraft's compass system was an AHRS and the reporter has noticed that the Inertial equipped aircraft seem to be somewhat more stable in the capture mode.