B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 180
Workload; Situational Awareness
Deviation - Altitude Crossing Restriction Not Met; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Human Factors
Captain was flying. We were just inside the WAHUU2 Arrival at FL380 when ATC issued a clearance to descend to FL340 and expect to descend via the WAHUU2. The Captain elected to start the descent by using Vertical Speed (VS) at 500 FPM then reinitialized the FMC to FL340 to place the FMC in a CRZ DESC mode; not VNAV PATH. She kept the descent going at 500 FPM.As we were approaching the new Top of Descent (TD) for FL340; we were at 35;500 feet MSL and I mentioned to the Captain we are going to be about 2;000 feet high above path unless we increase the rate of descent. The Captain elected to continue the slow descent as we passed the TD 1;500 feet above path and increasing while she stated not to worry. ATC then issued a clearance to descend via the WAHUU2. We were 2;500 feet above path. The Captain never engaged VNAV and elected to use VS to try and catch up to the path.As we were accelerating past 300 KIAS; I mentioned we are fast and need to maintain 280 KIAS per the note on the arrival. The Captain denied it at first; checked the chart looking for the note; found it; but continued to accelerate to catch the path in VS mode. I then requested ATC give us 'speed our discretion;' which they denied. We accelerated to 310 KIAS in VS. She never once engaged VNAV during the entire approach; putting my PM duties in the yellow to ensure we did not bust an altitude restriction. We finally got vectored off the WAHUU2 and landed uneventfully.The technique for Captains to use VS on published arrivals is still being practiced and places the PM in the yellow to crosscheck aircraft performance not to exceed published restrictions. There still remains a misunderstanding of how CRZ DESC works vs VNAV PATH; VNAV SPD; or VS. Please publish a training guide that is handed out or published on the Electronic Flight Bag (EFB) to clearly spell out the difference; with examples of each. There should be a comparison between CRZ DESC; VNAV PATH; VNAV SPD; and VS on the effects and impact to properly fly a published arrival with airspeed and altitude restrictions.
B737-700 FO reported the Captain; as the pilot flying; chose to use CRZ DESC mode rather than VNAV; and was having difficulty complying with the RNAV STAR constraints.