B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 190; Flight Crew Type 190
Human-Machine Interface; Situational Awareness; Workload; Distraction
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Overcame Equipment Problem; Flight Crew Became Reoriented
Airport; Weather; Procedure; Equipment / Tooling; Airspace Structure
We departed in a B737.The weather was gusty winds with IMC off the end of the runway. At 400 feet AGL; we engaged LNAV and confirmed LNAV to a fix. Passing approximately 6000 feet; I was distracted by my duties during a very high workload environment. I was contacting Departure Control; setting the thrust levers to climb thrust; retracting flaps; setting gear handle to Off; and placing autobrake switch to off.I then looked at my HSI and noticed we were off course to the right approaching one dot deflection. I then looked over at the FO's (First Officer) PF's (Pilot Flying) attitude indicator and saw the aircraft was in a 30 degree right bank turn. The F/O (PF) was following his flight director which was commanding a 30 degree right bank turn. I immediately directed the F/O (PF) to turn left; explaining we were off course. He complied and banked left disregarding the flight director commands. As we were trying to figure out why the flight director was giving us erroneous commands; NorCal Departure told us we were right of course and to turn to a heading of 110 degrees. Once we selected HDG SEL the flight director gave us correct commands.
We immediately went into the weather and were experiencing light to moderate turbulence (takeoff winds were 210/25G35). I was following my command bars and at approximately 6000 feet (approximately 1500 feet AGL) I realized I was in a right 30 degree bank turn going away from the course. At that moment; the Captain said we need to come back to the left. I immediately turned left to get back on the course (disregarding my flight director). Departure Control then asked if we were turning right and gave us a heading of 110 degrees. The Captain selected Heading Select and the command bars then showed a left turn. We got back on course and continued the flight. The command bars may have been trying to turn around back to ZEFFR or to the initial fix on the ZEFFR Departure. We reviewed all our procedures and cannot figure out what caused the command bars to turn right.Not sure if the cause was a B737 and the discontinuity of the SID Departure. Even though it was only a matter of seconds before I recognized there was a problem; then a few more seconds to decide what instrument was giving me the erroneous information; I could have done it quicker with the departure path in mind. In retrospect I will; in the future; bring the general heading of the path more to my crosscheck to back up the command bars. When flying the B737; into weather; into turbulence on takeoff into high terrain; be extra confident on approximate headings and departure track.
After a straight out departure in IMC from an airport surrounded by high terrain; the flight crew engaged the FMS and the aircraft made a right turn which was not immediately recognized as an error. The pilot monitoring and departure control advised of the incorrect heading. The flight crew was unable to identify why the FMS turned the aircraft to the right.