B737-300
Flight Crew Last 90 Days 127
Time Pressure; Human-Machine Interface; Workload
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Aircraft; Human Factors; Procedure
During descent on the OLYMPIA 7 just prior to the ARVAD waypoint; we were advised by Approach to expect the 16C ILS approach. Up to this point; we had briefed the 16R ILS; since that was the runway in use in the most current ATIS. So; as pilot flying; at approximately three miles from ARVAD; I reprogrammed the approach in the FMC. I unexpectedly experienced a problem when selecting the 16C ILS. The FMC displayed not only the approach; but part of the arrival as well. Specifically; it displayed all the points on the OLY7 from ARVAD and beyond. I tried to select the next point beyond ARVAD; that being FOURT; but I got an error message stating 'Altitude Restriction...'; and therefore; I could not execute the operation. So; thereafter; I line selected ARVAD from key L4 and used that to replace the current ARVAD at L1 (my fly to waypoint). As it turns out; I must have executed this operation very closely to actually passing over ARVAD; because thereafter; we continued on our northeasterly heading and flew right past the next turn point; FOURT. Approach Control noticed that we did not turn to heading 350 after FOURT as directed and depicted on the chart. Approach Control then gave us a vector to correct our ground track. The steering error did not cause any loss of separation with other aircraft. As well; the Controller did not ask us to contact him afterward. Since we were close to the airfield and in a busy phase of flight; I should have asked the pilot not flying to reprogram the FMC with the newly assigned runway. As well; even if I was to reprogram the FMC myself; I should have followed the standard procedure and ensured that the pilot not flying agreed with the programming change prior to me executing the action. Including both pilots in the programming would increase the likelihood of noticing any programming errors.
Just prior to the SEA OLYMPIA 7 ARVAD waypoint; ATC assigned ILS Runway 16C so the pilot flying changed the FMS runway from 16R and subsequently the track after ARVAD was dropped prompting ATC to issue a vector.