Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Confusion; Distraction; Situational Awareness
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings; Aircraft; Airport; Human Factors
On a vector to final; about 20 NM south of CLT; I observed the flight mode change from HDG to LNAV; then about 10 seconds later the flight director commanded a turn in the wrong direction. We were expecting all left turns to final; so when I saw the airplane starting to bank to the right; I immediately pressed the TCS button and leveled the wings.The first time that I saw this happen recently; I dismissed it as a fluke. But this has now happened to me 3 times at the same airport on different approaches. I would estimate this is happening on about 15% of all approaches to this airport now. It starts with a vector to the intermediate approach course; arming the LNAV mode; and shortly after switching modes the computer steers the airplane across the approach course; over-corrects back in the opposite direction; and then chases the CDI to a normal alignment.This error in navigation; even though semi-random in frequency; is of such concern that I have been briefing the risk of TCAS activations and NTZ [No Transgression Zone] incursions that could be caused by this computer glitch. At this airport; it is fair to assume that there is always traffic on the simultaneous parallel course. Today; I briefed this possibility with the pilot flying while at cruise; and his reaction when it happened; although not as fast as mine; was understandable. He thought the turn was at first a subtle deviation in the direction of the final course.
Air carrier pilot reported that the flight director commanded a turn in the wrong direction during approach to CLT airport.  Reporter advised; 'this has now happened to me 3 times at the same airport on different approaches.'