EMB ERJ 140 ER/LR
Flight Crew Commercial
Workload; Physiological - Other; Human-Machine Interface; Distraction
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Procedure; Chart Or Publication; Aircraft; Human Factors
[While descending via] the ALDAN arrival into RDU we missed the assigned crossing restriction for the final fix of BUTTS. We were task saturated in the cockpit and missed the crossing.Although not a direct influence on this event; the new RNAV procedures that include numerous altitude 'gates' (ceiling and floors) create an extremely high workload and cause task saturation in the cockpit. The FMS does not allow for us to assign multiple restrictions to a single fix; so many of the altitudes must be manually computed for the crossings. The task saturation from these crossings contributed by condensing the time available for additional flight duties.Amend the RNAV procedures to include single altitudes at fixes and not gates.
On descent into RDU via ALDAN 1 RNAV ARRIVAL there where 6 altitude crossing with combination of speed restrictions. We complied with all but missed the last fix restriction (crossing BUTTS at 6;000 FT). I think; I was under the impression we [were] going to be vectored for final before we reached BUTTS; but he [Controller] wanted us all the way down with RNAV arrival. As a result we missed BUTTS at 6;000 FT. We asked ATC if that crated any traffic separation conflict; and he replied 'Negative'.Event occurred because it was the first time I was using this arrival STAR; and I was unfamiliar with the approach plate; and also I didn't pay attention to the whole plate; and also task saturated due to the fact that we had multiple crossing restriction; in combination with performing checklists.Don't assume you are going to be vectored before you reach the fix!!! Be completely familiar with the approach plate ask for help from your pilot not flying to identify fixes and restrictions.
An EMB-140 flight crew failed to comply with the 6;000 FT MSL crossing restriction at BUTTS on the ALDAN RNAV STAR into RDU. Task saturation due to multiple crossing restriction restraints; in particular above/below windows; was cited as the primary contributing factor.