Date: 201810
Local time of day: 0601-1200
Location: DEN.Airport, CO
Flight conditions: VMC
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B DEN
ATC / advisory: TRACON D01
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Human-Machine Interface; Situational Awareness; Time Pressure
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: While descending on the JAGGR3 RNAV arrival into Denver; all was well with planned RNAV RNP 17R loaded in the FMC. We had been cleared to descend via the JAGGR3 and had a discontinuity between QWIKE on the arrival and QWIKE on the approach as we had never yet been cleared for the approach. Somewhere around JAAAM (I believe) Approach Control told us to slow early to 210 KTS. This put us a bit high on profile and we were having to react aggressively to make the 11000 at QWIKE. About the same time we were cleared for the RNAV RNP Z 17R approach. I selected QWIKE for the approach (below the discontinuity) and attempted to place it just below QWIKE on the arrival (above the discontinuity) but it would not take. I am not sure if there was an accompanying scratch pad message but I then selected QWIKE below the discontinuity and placed it on top of QWIKE above the discontinuity and got an execute light. Confirmed with the First Officer (F/O) and pushed execute. Still not sure exactly what went wrong but the jet did not start the turn at STAAM but instead went straight ahead. After a slight delay to see that the autopilot was not going to make the turn; I disconnected the autopilot and hand flew the airplane for the remainder of the approach as it was clear skies and near unlimited visibility with the runway in sight. Just after I disconnected the autopilot and was beginning the turn; ATC asked if we were flying the RNAV Z 17 R and the F/O replied 'yes'. No more was said and we continued to landing. I have little doubt that some mistake was made and the FMC was misprogrammed in the rushed environment that was created by ATC but am not sure what it was. I did realize after starting the turn that there was a magenta line that also continued straight ahead in addition to the curved magenta line of the approach but it was not readily noticed in the hurried state we had been suddenly put in. I will investigate further when back in an airplane and with ample time to do so. I would like to stress that I can't really think of a time while descending on a descend via arrival into Denver that Approach Control did not change things up from published at least once; and many times there are multiple changes. This happens all the time in Denver and from talking to other pilots it is common to everyone. I can understand the occasional need to change a speed or altitude but this seems to happen every single time on arrivals into Denver. I feel it has become a safety hazard and it is not just me. Many pilots feel the same. These arrival changes are often combined with late approach clearances just like happened in this case. Why can't Denver just clear us to descend via an arrival and cleared for the RNAV XXX approach like many other cities do in what seems like far more congested airspace?




Synopsis: B737NG Captain reported a track deviation occurred on the JAGGR3 arrival into DEN. Reporter stated a late clearance change in a time-limited situation led to an FMC programming error.