Commercial Fixed Wing
Communication Breakdown; Confusion; Human-Machine Interface; Time Pressure; Workload
Airspace Violation All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Chart Or Publication; Human Factors; Procedure
While I was working Sector 27 Radar the Cheyenne MOA/ATCAA was active FL290 and below with two F16 aircraft. An air carrier [Aircraft X] had been rerouted by a previous sector; Sector 46; direct JAGGR then the JAGGR2 arrival to DEN. The JAGGR waypoint has an altitude restriction FL300-340 and provides separation from the Cheyenne ATCAA. I cleared the [Aircraft X] to descend via the JAGGR2 arrival. I then noticed the aircraft descending below FL290 prior to the JAGGR waypoint and the aircraft was inside the lateral confines of the Cheyenne ATCAA. I climbed the [Aircraft X] back to FL300 and informed the pilot of a possible pilot deviation after advising the FLM of the possible pilot deviation. I later informed the pilot of the airspace violation with the Cheyenne ATCAA. The pilot responded saying when he was given the last minute STAR change; the altitude restriction at JAGGR had dropped out of the FMS; and it would be helpful if the controller would reiterate the restriction. The previous sector had rerouted the [Aircraft X] over to the JAGGR2 arrival as soon as the aircraft crossed the ZDV/ZKC boundary approximately nine minutes prior to JAGGR. The pilot later called the OMIC and told him the same thing as he said on the frequency.I recommend all RNAV SIDs/STARs be revised in and out of DEN to a simpler chart with fewer turns and restrictions. There has been too much confusion by pilots and controllers due to their complexity. Instead of reducing verbiage and workload; they have brought about more verbiage and questions from pilots when different speeds are assigned for spacing. There is too much information for pilots to go through; verifying every altitude and speed restriction for RNAV SID/STARs. I also; recommend this incident be brought to the attention of involved airlines. If data in the FMS is being dropped when changing STARs it causes serious safety issues.
[We were initially] cleared to descend via the ZPLYN RNAV STAR. Subsequently the clearance was changed to descend via the JAGGR arrival. Although we had previously verified crossing altitudes; for unknown reason the altitude restriction (JAGGR [Between FL340 and] FL300) required at this intermediate fix was not respected by VNAV. ATC queried and [directed us] to climb to FL300. A 2;000 foot deviation had occurred. At the time ATC communications were very busy. Also; the flying Captain was receiving IOE (first flight on [Aircraft X]) from a Check Airman. An additional flight deck distraction was a Flight Attendant in the cockpit regarding a cabin write-up. It is unknown why the [restriction] apparently dropped out of FMC.
In an excellent report the active ARTCC Controller and two pilots aboard which failed to comply with a crossing restriction on an RNAV STAR into DEN discussed the events preceding the deviation and the significant contribution to the error played by the complexity of the RNAV STARs. An additional contributing factor discussed is the potential for vertical navigation errors played by ATC alterations to those STARs. The Controller expresses his belief the existing RNAV STARs and SIDs need to be revised to be made more user friendly for both pilots and controllers.