A321
Air Traffic Control Fully Certified
Airspace Violation All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert
Procedure; Human Factors; Aircraft
The A321 checked on at FL300 and was flying the JAGGR1 arrival. Cheyenne MOA/ATCAA was active FL290 and below. Descending via the JAGGR1 ensures separation with CYS ATCAA by using altitude (requires aircraft to be FL300-340 after clear of CYS). I gave the A321 a clearance to descend via the JAGGR1 arrival. He was vertically above CYS but laterally within the confines. I noticed him start to descend while still in the lateral confines (I noticed at FL296) of CYS by approximately 4 miles. I amended his altitude to FL290 and explained to him that he started his descent too early; as he was required to cross JAGGR waypoint between FL300-340. Pilots [need] to understand fully the RNAV arrivals and clearances. Also; I am no longer going to issue the descend via clearance while the aircraft are laterally within the confines of CYS ATCAA anymore even though it ensures separation. I will wait until they are clear so if they start down early by mistake they won't bust military space.
Denver Center cleared us to descend via the JAGGR1 arrival. We programmed the FMS and confirmed 9;000 FT as the bottom altitude. The descent mode was initiated just prior to the JAGGR waypoint. The aircraft was at FL300 and the alt restriction at JAGGR is FL300. The aircraft should not have started a descent; but it did. At approximately FL295; both pilots and ATC noticed the error. Denver ATC issued a clearance to FL290 and resume the JAGGR1 arrival.
An A321 Captain and the ZDV Controller involved both describe an altitude deviation while the A321 crew is attempting to comply with the altitude restrictions of the JAGGR 1 RNAV arrival into DEN. The aircraft had responded to an MCP input in an unexpected way.