Narrative:

[We were] cleared into den on the ZPLYN3 arrival. The active modes were LNAV/VNAV. The crew was expecting and briefed RNAV Z 16L which was installed. At approximately 10-11000 ft; the crew was cleared for RNAV Z 17R. The right/west; approach with qwike transition; and arrival were installed. The arc turn beginning at staam was present and visible on the nd. As fix qwike was captured; the turn fix staam was no longer on the nd or fix page and new active waypoint became roool (a fix on the arrival but not on the approach). Still in LNAV; the aircraft was proceeding to roool even though the procedure arc was still present. The aircraft did not turn at staam. The captain (pilot monitoring [pm]) directed the first officer (pilot flying [PF]) to start the turnout of LNAV which he did in heading select. The captain re-installed the approach with the goal of re-engaging LNAV. During this; the first officer was flying the aircraft on [heading] sel back onto the arc which had remained visible during the entire event. Approach radioed the first correction call at the exact time the crew had started the [heading] sel turn having recognized the turn had not commenced. Pm reported [we were] in a turn. A second ATC radio call was made despite the response which was again answered. At this point approach canceled approach clearance and directed [us] to turn right 340 degrees and descend to 8000 ft. Once again the crew responded in compliance but ATC repeated the instructions. Pm responded again. A third ATC radio call instructed [us] to turn left 260 degrees and descend to 7000 ft and cleared for visual approach. For the third time; pm responded however the radio call was repeated and acknowledged. [We were] switched to tower and cleared to land and taxi to gate with no radio problems. On debriefing; the crew discussed the re-emerging of STAR fix roool as the active fix after qwike capture. We discussed the possibility of the aircraft not turning because the jet had an un-modifiable active waypoint (roool) at the moment the new approach was selected and activated. Approach requested to be contacted. The captain spoke with supervisor to discuss the event. [Supervisor] advised that den was having '2 to 3 deviations daily' on the Z RNAV approaches. They were filling out internal deviation reports and debriefing with the crews. He asked for input on possible causes. The captain mentioned the described navigation anomaly; the late approach clearance (just outside qwike) along with possible controller comm problems (three separate repeated and acknowledged controller instructions) as potential causal factors. Crew recommends simulator re-enactment to investigate LNAV functionality with regards to RNAV Z 17R being activated at the critical point of just outside IAF capture.

Related reports:

Google
 

Original NASA ASRS Text

Title: B757 Captain reported a track deviation occurred on the RNAV (RNP) Z Runway 17R Approach in DEN; following a late clearance change and an FMC anomaly.

Narrative: [We were] cleared into DEN on the ZPLYN3 Arrival. The active modes were LNAV/VNAV. The crew was expecting and briefed RNAV Z 16L which was installed. At approximately 10-11000 FT; the crew was cleared for RNAV Z 17R. The R/W; approach with QWIKE transition; and arrival were installed. The arc turn beginning at STAAM was present and visible on the ND. As fix QWIKE was captured; the turn fix STAAM was no longer on the ND or fix page and new active waypoint became ROOOL (a fix on the arrival but not on the approach). Still in LNAV; the aircraft was proceeding to ROOOL even though the procedure arc was still present. The aircraft did not turn at STAAM. The Captain (Pilot Monitoring [PM]) directed the First Officer (Pilot Flying [PF]) to start the turnout of LNAV which he did in Heading Select. The Captain re-installed the approach with the goal of re-engaging LNAV. During this; the First Officer was flying the aircraft on [HDG] SEL back onto the arc which had remained visible during the entire event. Approach radioed the first correction call at the exact time the crew had started the [HDG] SEL turn having recognized the turn had not commenced. PM reported [we were] in a turn. A second ATC radio call was made despite the response which was again answered. At this point Approach canceled approach clearance and directed [us] to turn right 340 degrees and descend to 8000 FT. Once again the crew responded in compliance but ATC repeated the instructions. PM responded again. A third ATC radio call instructed [us] to turn left 260 degrees and descend to 7000 FT and cleared for visual approach. For the third time; PM responded however the radio call was repeated and acknowledged. [We were] switched to Tower and cleared to land and taxi to gate with no radio problems. On debriefing; the crew discussed the re-emerging of STAR fix ROOOL as the active fix after QWIKE capture. We discussed the possibility of the aircraft not turning because the jet had an un-modifiable active waypoint (ROOOL) at the moment the new approach was selected and activated. Approach requested to be contacted. The Captain spoke with Supervisor to discuss the event. [Supervisor] advised that DEN was having '2 to 3 deviations daily' on the Z RNAV Approaches. They were filling out internal deviation reports and debriefing with the crews. He asked for input on possible causes. The Captain mentioned the described navigation anomaly; the late approach clearance (just outside QWIKE) along with possible controller Comm problems (three separate repeated and acknowledged controller instructions) as potential causal factors. Crew recommends simulator re-enactment to investigate LNAV functionality with regards to RNAV Z 17R being activated at the critical point of just outside IAF capture.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.