Date: 201301
Local time of day: 0601-1200
Location: ZDC.ARTCC, VA
Flight conditions: VMC
Light: Daylight
Aircraft: Citation X (C750)
Operator: Corporate
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
ATC / advisory: Center ZDC
Aircraft component: Autoflight System
Component problem: Design; Improperly Operated
Reporter organization: Corporate
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Communication Breakdown; Human-Machine Interface; Situational Awareness; Training / Qualification; Distraction; Workload; Troubleshooting
Second reporter function: Captain; Pilot Not Flying
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Critical; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem
Contributing factors: Human Factors; Chart Or Publication; Aircraft; Procedure
Primary problem: Human Factors

Narrative: Our clearance included the GIBBZ RNAV STAR into IAD. When we were way above the descent path; the Controller cleared us to descend via the arrival. I pushed direct to the next altitude in the FMS to try to bring back the pink vertical guidance in order to engage VNAV and that next altitude went away. Can't really explain why that happened.As a result the pilot not flying had to pull the arrival back out of the iPad and it took a while to get the correct first altitude for the descent. We descended as steeply as we could with speed brakes but we went a little past the fix before we got to the right altitude. They were all below and above altitudes; we could never get the VNAV in a position to engage so the non flying pilot had to keep putting in altitudes manually which I think we hit OK after the first one except for one problem - while hurrying down and trying to get all the altitudes put in manually we didn't reset the altimeter passing FL180. We weren't neglecting the checklist; we were just surprised that VNAV wouldn't engage and were so busy manually managing that quick descent. I think we were probably OK because the pilot not flying put the middle altitudes between the limits and I think we hit those pretty well; but it was the sloppiest descend via I've ever done with the speed not too consistent either. The Controller never said anything; I hope he realized he put us in a bad position on that first descent and there was no conflict.I should have had my iPad out on the arrival and been briefing that the VNAV might not take since we were well above the TOD for that arrival. We speculated afterwards that the box didn't like direct the next altitude because it had between this and that altitude listed so it probably didn't know what I wanted and just took both altitudes out because of that. We've got to make sure we don't lose the most important chart in the iPad or put it to sleep when we might need it also. Mostly I think we were both too relaxed because we had verified and briefed all the altitudes and speeds in the box and it usually works so well. I trusted that the VNAV would work when we were beyond its limits and I should have been more keyed up for that arrival when we didn't start down on schedule. Also I should have told ATC when I began to doubt we could make that first fix. I don't know how well it would have gone over to say we are having a programming problem; unable to descend via but that thought also crossed my mind.


Second narrative: The pilot flying was meeting the altitudes with VNAV until he pressed direct to the altitude on the FMS for the MIIIK; which was to cross between FL190 16;000 feet. As soon as he pressed it VNAV disengaged and all altitudes dropped out of the FMS. I was working on getting the altitudes back in the box but stopped to help him get back on track. We crossed MIIIK somewhere close to 19;000 feet. As we were working together on making sure we made all the rest of the speed and altitudes; we forgot do to the approach checklist until below 10;000 feet. The altimeters were at 29.92 and should have been at 30.30. So our crossing altitudes may not have been correct.


Synopsis: When a CE-750 flight crew failed to initiate a timely descent on the GIBBZ RNAV STAR to IAD the FMS lost all altitude and airspeed constraints and the crew distractions which resulted were significant including failure to QNH passing FL180 and forgetting to do SOP arrival checklists. Crossing restrictions were also problematic and deviations were likely if for no other reason than the altimeter setting which would have produced about 500 foot errors.