EMB ERJ 135 ER/LR
Flight Crew Air Transport Pilot (ATP)
Distraction; Human-Machine Interface; Workload
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem
Procedure; Human Factors; Chart Or Publication; Aircraft
[When descending via the] FRDMM ONE RNAV arrival with autopilot on and NAV selected; when you pass FRDMM Intersection the autopilot NAV mode clicks off and goes to roll mode. Had we not been paying attention to it and rearmed NAV mode we would have gotten off course. This is the second time this has happened in a different plane. Also the FRDMM ONE RNAV STAR is very distracting to the point were it seems like one pilot's FULL attention is necessary to meet the step down restrictions and half the other pilot's attention is on it; too. This distraction could cause crews to miss something. This STAR might be a good approach for the 170/175 jets but on a 145 it is very distracting trying to make all the altitudes work out right.Fix the software in the FMS or don't file us for the FRDMM STAR.
When flying the FRDMM RNAV STAR to DCA an E-145 Captain advised the FMS NAV mode reverts to the ROLL mode when passing FNCHR and must be re-selected to continue to track the arrival. The reporter also cited excessive complexity of the many crossing restrictions required by the STAR which demand excessive attention by the flight crew during a critical phase of flight.