B737-300
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 53; Flight Crew Type 26000
Human-Machine Interface; Situational Awareness
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC Overrode Automation; Flight Crew Returned To Clearance
Aircraft; Chart Or Publication
We were cleared to descend VIA KOHOE ONE RNAV Arrival. I had updated the Descent page on the FMC to increase the descent speed to 280 KTS. 74/280 KTS was entered on the speed line. Approaching HERNG; I noticed that we were at .74M (265 KTS) prior to the speed changeover. I advanced the throttles to compensate; but we were about 10 KTS slow at HERNG. Subsequently; I was able to keep the speed up until the speed crossover point where we were programmed for 280 KTS.An RNAV arrival should not require an acceleration to a greater than normal cruise speed at the Top of Descent. I guesstimate that to show 280 KTS at HERNG; I would have to program .78M or greater to get 280 KTS on the indicated side. Is that what is really wanted? How far in advance of HERNG should I switch from econ cruise to .78M or greater?
A B737-300 Captain found it necessary to accelerate from his standard cruise speed in order to comply with the crossing airspeed required at HERNG while descending via the KOHOE RNAV STAR to DEN.