Narrative:

Maintenance worked on the FMS #2. We tested it before flight in front of the mechanic and it worked fine. It was the first officer leg and the first officer briefed the departure from the box and I followed him with the chart on the ipad. Everything checked. We emphasized that the initial turn is to the left to the VOR. Taking off on runway 19R the first officer turned left and on course; at acceleration altitude the first officer asked for climb sequence and I proceeded to complete the items; including autopilot engaged as previously briefed. My head was down running the after takeoff checklist when I felt the jet turning right; I said 'where are you going' and I took over the jet and disconnected the autopilot and started the turn to the left. My FD disappeared and I asked the first officer to give me direct to the VOR while telling ATC that we had a FMS malfunction and we needed vectors. They said they were unable until we reached a certain altitude. I level off at 4000 ft as per the departure and we were able to get FD #1 back. No altitude was busted and then we proceeded on course. When we landed I called approach and I asked them if we had violated any airspace and I explained the FMS situation. They said that we went to the south a little too far but that they were able to coordinate with the TRACON and that they saw no problem with the event because it was an FMS malfunction. Maintenance has been notified and it has been written up. My debrief to the first officer was that the departure procedure was well known and regardless of having the autopilot connected; always have situational awareness and never rely on the autopilot. Today was a perfect example of not relying on automation and always crosscheck every turn the autopilot is taken. The VOR as on magenta meaning it was supposed to keep turning to the left nevertheless the autopilot initiated a turn to the right at about 1200 ft MSL and it happened so fast the first officer didn't notice until I did and I took over the plane. The first officer fully understands and a lesson has been learned for both us. From now on I will reinforce this lesson to other pilots I fly with.

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Original NASA ASRS Text

Title: An EMB-135 Captain reported an FMS malfunction while on a SID that resulted in a course deviation.

Narrative: Maintenance worked on the FMS #2. We tested it before flight in front of the mechanic and it worked fine. It was the First Officer leg and the First Officer briefed the departure from the box and I followed him with the chart on the iPad. Everything checked. We emphasized that the initial turn is to the Left to the VOR. Taking off on RWY 19R the First Officer turned Left and on course; at acceleration altitude the First Officer asked for climb sequence and I proceeded to complete the items; Including Autopilot engaged as previously briefed. My head was down running the after takeoff checklist when I felt the jet turning right; I said 'where are you going' and I took over the jet and disconnected the autopilot and started the turn to the left. My FD disappeared and I asked the First Officer to give me direct to the VOR while telling ATC that we had a FMS malfunction and we needed vectors. They said they were unable until we reached a certain altitude. I level off at 4000 ft as per the departure and we were able to get FD #1 back. No altitude was busted and then we proceeded on course. When we landed I called Approach and I asked them if we had violated any airspace and I explained the FMS situation. They said that we went to the south a little too far but that they were able to coordinate with the TRACON and that they saw no problem with the event because it was an FMS malfunction. Maintenance has been notified and it has been written up. My debrief to the First officer was that the departure procedure was well known and regardless of having the autopilot connected; always have situational awareness and never rely on the autopilot. Today was a perfect example of not relying on automation and always crosscheck every turn the autopilot is taken. The VOR as on magenta meaning it was supposed to keep turning to the left nevertheless the autopilot initiated a turn to the right at about 1200 ft MSL and it happened so fast the First Officer didn't notice until I did and I took over the plane. The First Officer fully understands and a lesson has been learned for both us. From now on I will reinforce this lesson to other pilots I fly with.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.