Date: 201808
Local time of day: 1201-1800
Location: DEN.Airport, CO
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B DEN
ATC / advisory: TRACON D01
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Distraction; Situational Awareness
Anomaly: Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: Due to the weather in Denver; the last third of the flight was very busy as we were given holding twice; assigned different arrivals; and were coordinating with Dispatch for alternate planning. As we approached Denver; the weather cleared out and the Approach Controller initially told us to expect the Visual to Runway 16R. A few minutes later he offered us the RNAV (RNP) Z to Runway 16R. We accepted his offer and programmed and briefed the approach. We were in visual conditions with good visibility. While we were level at 13;000 FT; I re-cruised the FMC and then we were given a descent to 11;000 FT and cleared for the approach. I selected 11;000 FT and pushed the Altitude Intervention button and the aircraft would not descend. A scratch pad message popped up; but due to the close proximity of the fix; I quickly re-cruised the airplane for 11;000 and 210 kts and the airplane started descending at 1;000 feet per minute. The FMA stated LNAV and VNAV PATH and I selected 10;000 FT as it was the next lower altitude on the approach. I don't recall the VNAV PATH deviation scale appearing and the range to altitude green line was showing us high and missing our mandatory altitude of 11;000 FT at CLFFF intersection. Noticing this; I selected Vertical Speed in order to make the restriction; but I failed to reset the altitude in MCP to 11;000 FT for compliance at CLFFF. ATC had called out Company traffic passing from right to left 1;000 FT below us. We got the traffic in sight and ATC told us to maintain visual separation with the traffic. Locating the traffic got me distracted; and when I went to crosscheck my descent I noticed that we were at 11;000 FT and still descending. I immediately disconnected the autopilot in order to level off the aircraft and we descended approximately 260 FT below our assigned altitude. We were able to climb back up to 11;000 FT and meet our mandatory altitude assignment at CLFFF. ATC did not say anything and the rest of the approach was normal. Any time Vertical Speed is used; the altitude in the MCP needs to be crosschecked and reset if needed in order to be in compliance with altitude restrictions. This will protect the crew from any altitude deviations. Although looking for traffic is important; I should have let the Pilot Monitoring do that as I was busy trying to get the aircraft to comply with the altitude restriction. It was evident that I was not able to divide my attention at the time. I should have gotten the aircraft in order and then helped my Pilot Monitoring look for the traffic. Better division of time and attention would have been beneficial.




Synopsis: B737-700 First Officer reported overshooting an altitude restriction on the RNAV (RNP) Z approach to DEN Runway 16R. Lack of mode awareness was cited as contributing.