B737-800
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Distraction; Human-Machine Interface; Situational Awareness
ATC Issue All Types; Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Human Factors; Procedure
On our flight to IAD the First Officer's FMC Display was previously placarded by another crew. Prior to descent; because of the placarded FMC and the filed GIBBZ1 arrival; I had made the decision--because of safety and crew workload--to not accept a 'descend via' clearance. While on Cleveland Center; the flight was cleared to cross BRNDN at FL290. Upon reaching FL290; we were switched to Washington Center.Immediately upon check-in; I informed the Controller that we were unable to descend via the GIBBZ arrival because of a placarded FMC. The Controller told us he was going to have to vector us for a different arrival. We were given vectors to FINKS for the DOCCS1 arrival at IAD. The Controller questioned why we accepted the RNAV arrival from Cleveland Center. At the time we were with Cleveland Center; I had not made a final decision to not accept a 'descend via' clearance. Cleveland had not cleared us for the approach or to 'descend via' the GIBBZ arrival prior to switching to Washington. While on the DOCCS1 arrival; after a frequency change to Potomac Approach; the Controller was confused by the arrival we were on; apparently because he did not receive information about our arrival change from the GIBBZ1. The remainder of the approach and landing were uneventful.The FMC placard specifies no RNAV (RNP) approaches authorized. Although we were not on an RNP approach; because of only one FMC and the intensive descent profile of the GIBBZ1 arrival; I made the decision to not accept a 'descend via' clearance for safety and crew workload. We told center that we could still fly the lateral navigation. Since the MEL did not preclude RNAV arrivals; we could have flown the approach as filed. We could have also informed one of the center controllers prior to Washington Center to give them a heads up; but the final decision to not accept the descent profile was not made until just prior to the switch to Washington Center.
Although technically legal to do so; B737-800 Captain advised ATC the flight was unable to descend 'via' the GIBBZ RNAV STAR to IAD due to a deferred FMC component and requested an alternative arrival. His decision was based on excessive flight crew workload associated with the complex RNAV STAR's multiple speed and altitude restrictions.