B737 Undifferentiated or Other Model
Flight Crew Last 90 Days 200; Flight Crew Total 20000; Flight Crew Type 7000
Situational Awareness; Human-Machine Interface; Distraction; Confusion
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Aircraft
On the ground before departure we loaded the route supplied by the flight plan. After receiving an updated clearance; we loaded the new route. The new route included the WYNDE 4 arrival into ORD. En route to ORD the First Officer briefed the arrival and runway that was selected to land in ORD. The route was double checked by both of us. Somewhere around the FNT VOR; it appeared that the FMC had a momentary malfunction. The route came up but before we could check the route; we had passed FNT and the FMC started toward DEWIT Intersection. The Controller asked if we were heading toward EMMMA Intersection that was on the arrival. I responded that we were past EMMMA as; (looking at the FMC) EMMMA Intersection had disappeared. The Controller advised that we were 3 miles southeast of EMMMA. He then cleared us to GRR to rejoin the arrival. The First Officer entered GRR in the FMC and we proceeded to GRR. I asked the Controller is there were any separation problems; and he responded NO and there were no problems. Since we were within 3 miles of EMMMA when the problem was resolved; it appears that there were no pilot deviations before the correction. As for the FMC; it appeared that EMMMA and LTOUR intersections had disappeared. GRR was in the box and the First Officer just brought up GRR to get back on the arrival. I made a logbook entry as to the failure of the FMC.
A B737 FMS dropped a WYNDE 4 RNAV segment immediately after FNT and proceeded to a DEWIT Intersection which was not on the flight plan. ATC caught the deviation and cleared the flight direct GRR.