B737 Undifferentiated or Other Model
Human-Machine Interface; Confusion; Workload
ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Speed All Types
Air Traffic Control Issued New Clearance
Chart Or Publication; Human Factors; Procedure
On ZPLYN RNAV STAR cleared direct to QUAIL and already in the descent to cross QUAIL at ZPLYN altitudes (FL220-FL200). We were then cleared the BOSSS arrival and to descend via the BOSSS (QUAIL between FL190-17000). The FMC will not change the old altitudes to the new BOSSS altitudes while proceeding direct to QUAIL. We spent too much time heads down trying to get the new ones into the box. It will not happen! The only way to get the new altitudes in is to go into heading select mode; go direct to a waypoint behind you and activate it; then move QUAIL back to the active waypoint and activate it; then back into LNAV. HUGE THREAT! Since we were [now] higher than we needed to be ATC also wanted us to slow down. WE CANNOT SLOW DOWN AND STILL DESCEND; ATC NEEDS TO KNOW THIS. We did not violate any crossing restrictions but were too high and fast to fit in so we were vectored for a downwind leg and resequenced into the approach flow. All could have been avoided if there were no conflicting altitudes on the arrival procedures; if the FMC would program itself correctly; if ATC would give a more [reasonable] clearance change; if all of the [new] DEN arrivals and transitions were thrown out and the old were used again; if ATC would just let you fly the entire procedure without vectors off course. Another HUGE threat is having higher altitudes on the transitions than those on the STAR! Who came up with that one?  With higher altitudes on the transition than the STAR the FMC will not let you go into an active mode. HUGE THREAT and too much time spent heads down reprogramming.
A B737 captain expressed general umbrage toward the recently initiated 'OPD' RNAV STARs to DEN. In the specific incident referenced they had been cleared direct to cross QUAIL as charted (Between FL220 and FL200) on the ZPLYN RNAV STAR; thence to descend via the STAR. Subsequently they were recleared via the BOSSS RNAV STAR via direct to QUAIL and to cross as charted; between FL190 & 17;000; but were unable.