Cessna Citation Sovereign (C680)
Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 35; Flight Crew Total 11251; Flight Crew Type 2100
Situational Awareness
ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
General None Reported / Taken
Human Factors; Procedure
The flight progressed normally until we were given the clearance to fly the GIBBZ 2 arrival and to descend via the GIBBZ 2. This occurred approximately 8 miles west of JIMVE intersection. We were at FL280 with clearance to cross JIMVE at flight level 210. The rate of descent to make that happen was not reasonable or normal for passenger comfort. I believe we missed the crossing restriction.Flying into Washington Dulles (IAD) often; we have experienced the controllers giving us the arrival with a descent via only to be vectored off course or a different altitude than required.  This plays havoc with the avionics system trying to keep up or possible input errors in the reprogramming process which requires the pilot to manually fly the aircraft. I believe once the arrival clearance is given with descend via. If any changes are required they should be vectors to and descents to fixes and the original clearance not reissued.
Flying into Washington Dulles (IAD) often; we have experienced the Controller giving us the arrival with a descend via only to be vectored off course or a different altitude than what is published. This plays havoc with the FMS SYSTEM attempting to keep up. At times even requiring the Pilot to hand fly the arrival. This in turn creates a heavier workload for the crew. I believe once the arrival clearance is given with via descend; if any changes are required they should be vectors to descents to fixes and the original clearance not reissued. If the clearance was unrealistic the crew should notify the Controller immediately however. These arrivals are designed to reduce workload for the crew as well as for the Controller if applied properly.
CE680 Flight Crew laments the numerous changes issued by PCT after assigning a descend via clearance.