Medium Transport; Low Wing; 2 Turbojet Eng
Flight Crew Last 90 Days 100; Flight Crew Total 15000; Flight Crew Type 94
Workload; Distraction; Human-Machine Interface
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert
Aircraft; Human Factors; Procedure
I was one of two IROs on our flight to DEN. We were filed and cleared to descend VIA the MOLTN RNAV STAR. Early in the arrival phase; we were told to expect the ILS Runway 34R. About 3-4 miles prior to HIMOM fix on the arrival; we were told to change our approach to THE RNAV Z 34L. Almost immediately we were given the clearance; 'at HIMOM cleared the RNAV Z 34R.' [Predictably] the aircraft's FMS and mouse pad cursor allows nothing to happen 'quickly' in setting up the FMS for last minute approach changes. Being ONLY a 'few miles' from the RNAV Z IF [Initial Fix] (HIMOM) it took us time to set up the approach and sequence the legs page so that the automation [matched our clearance]. In doing so; we flew past HIMOM; and the autopilot did not sequence correctly [via the approach transition] HIMOM; MCMUL; BSAYN; etc. The plane kept tracking south past HIMOM. The crew and ATC coordinated a southerly vector with by which to set up for a Visual Approach to Runway 34R. To our knowledge traffic separation was never lost and the approach was completed without incident.
In setting this up there was apparently an overlap created in the FMC at HIMOM; and when executed; both the segment continuing to KALME and beyond on the MOLTN2; and the HIMOM approach transition to MCMUL and KUGLN etc were showing magenta and active.
A late runway change clearance as the airliner was only a few miles from the runway transition IF resulted in a temporary track deviation as the flight crew attempted to program the change. ATC provided vectors for the subsequent approach.