Date: 201511
Local time of day: 1801-2400
Location: DEN.Airport, CO
Flight conditions: VMC
Light: Night
Aircraft: Large Transport
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)
Human factors: Communication Breakdown; Confusion; Distraction; Situational Awareness; Workload
Anomaly: Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
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: I was PF and descending on the CREDE3 into Denver. We were expecting runway 16R; which I have not landed on many times due to the fact that I generally fly trips on the east coast. I had programmed the ILS 16R but the captain switched it to the RNAV 16R before we heard anything from ATC; saying that 'we always get the RNAV when you're landing 16R.' I have not flown many RNAV RNP procedures and the Captain was explaining how to manage speed and configuration in light of the fact that all the arrival speeds had been deleted except for CLFFF at 11;000 and 210 knots. Without asking if I was comfortable with it; the Captain had me at 280 until just prior to CLFFF; while still descending. With full speed brakes I was just able to get on profile and cross CLFFF at 11;000 and 210. Being so engrossed in trying not to screw up the approach; I selected the APP pushbutton without having yet been cleared for the approach. We were approximately 10;600 when the Captain noticed my error and pushed to level off. We returned to 11;000 and landed without incident or ATC inquiry. I think I was so engrossed in planning for what the Captain insisted would happen and getting the aircraft down and slowed in time according to his plan rather than mine that I made the mistake of beginning the approach without clearance. The mistake was 100% mine alone and I know better than this but I think I was spring-loaded for the RNAV. Our briefing for the arrival was minimal and that also contributed to the confusion at CLFFF.Unless one pilot is really screwing something up; the other should not impose his/her flying style during critical phases of flight; as this distraction set me up to make an error that I've never made in my life. If a Captain doesn't like the way an First Officer is doing something; they should fly the aircraft themselves; and as the First Officer; next time I will pass control to the Captain if they are uncomfortable letting me fly my own leg my own way. Arguing about how to do something should only be done on the ground or in cruise. The different levels of experience on type can be a huge wedge for CRM; and though I am grateful to the Captain for backing me up and catching and mitigating my error; I feel like he added unnecessary complication and stress at a critical phase of flight which set me up to make this dumb mistake in the first place.Again; the mistake was completely mine and I took ownership of it.




Synopsis: On the CREDE3 arrival to the RNAV 16R at DEN; the First Officer prematurely selected Approach and started a descent before being cleared for the approach.