Date: 201507
Local time of day: 1201-1800
Location: DEN.Airport, CO
Flight conditions: Mixed
Weather elements / visibility: 10
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZDV
ATC / advisory: Center ZDV
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: First Officer; Pilot Not Flying
Anomaly: ATC Issue All Types; Deviation - Speed All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Human Factors; Procedure; Weather
Primary problem: Ambiguous

Narrative: To begin with; the descent and approach were planned and briefed prior to Top of Descent. The clearance was to descend via the CREDE 3 RNAV Arrival for a south landing. Unsure of the runway to expect (16L or 16R) I had briefed flying the arrival with vectors to a visual approach. I expected and briefed the ILS backup for the visual approach to 16L. Between CREDE and POWDR it was necessary to make slight deviations from course to avoid cumulus build ups. ATC was advised. As a result of the off course deviations it appeared that we might have a problem complying with the speed restriction at POWDR. We asked for relief from the restriction and were told to comply with the altitude restriction and 'do your best on the speed'. We were in compliance on the altitude; but about 15 knots above the 250 knot crossing restriction and quickly came within speed compliance. After that; the real challenge began. It was becoming obvious that ATC was under the gun. We were handed off to the Final Controller around MOGLS. The female Controller; speaking very fast; issued us a clearance for an RNAV Z Approach to 16R. This was unusual in that in all previous RNAV approaches I've made; it was because we asked for it. Nevertheless; it was unclear what she said with her rapid verbiage; so the FO asked her to repeat the clearance; which she did speaking even faster it seemed. This is the point where there was misunderstanding between the FO and me. I believed that she had given us the RNAV Z to 16L and was busy reprogramming the FMC; while the FO was receiving the approach clearance for the second time. When that was done; and after the FO was finished on the radio; he asked me to brief the approach. We did it by the book; I briefed all the points from the CDU (FMC) while he verified it on the EFB (iPad) chart. There were more radio distractions at the end of the brief. The airport was VMC with good visibility during the approach. I clearly saw the preceding traffic for 16L reported four and a half miles ahead. It was my understanding that I would follow him to 16L. However; the FO correctly believed our intended runway was 16R. When Tower cleared us to land on 16R; I thought that it was a late runway change so I disconnected the autopilot and autothrottles and adjusted my flight path to line up and land on 16R as cleared. It wasn't until later that I was able to determine that we were indeed cleared for the RNAV Z 16R. The first three points: CLFFF; CEPEE; and AAGEE are the same on both approach charts which is why the FO thought I was briefing the correct approach.The First Officer was outstanding in his duties as Pilot Monitoring. It was because of his diligence in speaking up that we were able to navigate what seemed like a mine field on the arrival. The female Controller was; because of her rapid fire clearance; very hard to understand and the pace in which she spoke contributed to the rushed feeling that we all had. RNAV approaches are very helpful and contribute to overall safety when planned and properly briefed in an unhurried environment. If it is the intent of ATC to have everyone flying RNAV approaches; it should be so advised in the ATIS if possible and not given so close in that it can't be properly briefed.


Second narrative: We were given instruction to descend via CREDE 3 at approximately FL320. This descent point put us slightly above the descent path. Additionally; we also requested a slight deviation due to a weather buildup. The radios were very busy at the time and it was difficult to transmit/receive. Once we were given the weather deviation clearance and very early on in the descent profile; we determined we were high on the PATH and most likely would miss the crossing restriction at POWDR (at 250 knots between FL220 and 17;000'). I immediately asked for crossing altitude relief. Following our request for relief; the Controller immediately responded; 'I don't understand; I gave you instructions to descend via.' At this point; we continued to attempt to make the crossing restrictions. About 30 seconds later; the Controller came back and said; 'make the altitude; and do the best you can with the airspeed.' We made the crossing restriction altitude at POWDR at FL220; but crossed at approximately 267 knots. We essentially were given relief and made the Controller's new instructions. We made all further restrictions. Following this event; Approach Control gave us an approach type just short of CLFFF that was not in the ATIS; nor was one that we had expected or briefed; RNAV (RNP) Z Runway 16R. In addition; the radio traffic was extremely busy at the time and the Controller had to state the approach clearance three times due to breaks in the transmissions. It was not the approach we had loaded nor briefed. The Captain; who was flying the approach; quickly loaded the approach and very quickly briefed it. At the time; the radio traffic continued to be heavy. In my mind; we were cleared the RNAV (RNP) Z Runway 16R; but due to all the radio traffic and late changes; I made a call at CLFFF to the Controller for mutual verification. I said; 'CLFFF; commencing the RNAV (RNP) Z Runway 16R approach.' A non-standard call; but I had a feeling that there was some confusion. She said 'Roger.' This gave me assurance we were flying the correct approach. Just shy of AAGEE; the Approach Controller switched us to Denver Tower. I checked in and we were cleared to land on 16R. This is what I had expected. At that point the Captain said; I thought we were landing on 16L. I said no and queried the Tower Controller. The Tower Controller re-stated; 'Cleared to land on 16R.' At this point it was discovered that the Captain had thought we were given the clearance for the RNAV (RNP) Z to 16L. Fortunately; we caught the error prior to AAGEE and since both approaches share the same track and point up to AAGEE; it's very unlikely we violated any airspace. There is a difference of 100 feet between the two approaches; so a slight altitude deviation may have occurred. The error occurred because the Captain and I did not have a shared mental model of what we were cleared for. In addition; when the Captain briefed the approach; I did not catch that the incorrect approach was loaded and did not hear the difference between the two approaches due to the heavy radio traffic; my perceived expectation of what he was briefing and was cleared to fly (RNAV RNP Z 16R); along with the rushed nature of our clearance. We corrected the error and landed on 16R without further incident. Be ready for all approaches and ensure there is adequate Crew coordination between Crew Members. If the briefing is rushed or a situation dictates; spend the extra time to brief the approach; even if it means asking for a different approach (visual) or asking for vectors back around the approach corridor to garner more time.


Synopsis: B737-800 Flight Crew reported misunderstanding an approach clearance to Runway 16R at DEN due to a last minute assignment of an RNAV approach when an ILS or visual was expected. The frequency was also very congested and the Controller was speaking rapidly. The clearance was for the right runway but the Captain heard the left and programed the FMC that way. This error was detected and corrected before a significant deviation resulted.