ZLA center controller reported that two aircraft were being stepped down and the higher aircraft des...

Narrative:

Aircraft X was on the JANNY3 arrival. Aircraft Y was level at FL200. I was stepping aircraft X down reference aircraft Y. Aircraft X was pulling out in front of aircraft Y and had been cleared to FL210. The pilot questioned the clearance which I restated and which he read back. Separation was lost when aircraft X continued to descend. I instructed him to climb and maintain FL210 and told him that he'd only been cleared to FL210. I apologized to him twice for the confusion associated with the new procedures we have at ZLA. Later; when I walked up to the operations manager in charge; he was taking the phone call from the pilot. The pilot didn't understand that the altitude assignment overrode the descend via procedure.in this case; it appears pilots are not being adequately trained in descend via procedures. Somehow; they are not getting the information they need. I don't know who is responsible for the training of corporate pilots but they have been failed by the system. This is without question a very serious safety issue. As a controller who loves what I do and the pilots I do it for; it is heartbreaking to have a pilot deviation in my sector. I would much rather be the one who made the mistake. The video and audio recording of this incident proved that; as the omic told me; I 'did everything right.' there is absolutely no comfort in that.

Original NASA ASRS Text

Title: ZLA Center Controller reported that two aircraft were being stepped down and the higher aircraft descended to an altitude they were not given; leading to a loss of separation.

Narrative: Aircraft X was on the JANNY3 arrival. Aircraft Y was level at FL200. I was stepping Aircraft X down reference Aircraft Y. Aircraft X was pulling out in front of Aircraft Y and had been cleared to FL210. The pilot questioned the clearance which I restated and which he read back. Separation was lost when Aircraft X continued to descend. I instructed him to climb and maintain FL210 and told him that he'd only been cleared to FL210. I apologized to him twice for the confusion associated with the new procedures we have at ZLA. Later; when I walked up to the Operations Manager in Charge; he was taking the phone call from the pilot. The pilot didn't understand that the altitude assignment overrode the Descend Via procedure.In this case; it appears pilots are not being adequately trained in Descend Via procedures. Somehow; they are not getting the information they need. I don't know who is responsible for the training of corporate pilots but they have been failed by the system. This is without question a very serious safety issue. As a controller who loves what I do and the pilots I do it for; it is heartbreaking to have a pilot deviation in my sector. I would much rather be the one who made the mistake. The video and audio recording of this incident proved that; as the OMIC told me; I 'did everything right.' There is absolutely no comfort in that.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1431591
Time
Date	201703
Local Time Of Day	1801-2400
Place
Locale Reference	ZLA.ARTCC
State Reference	CA
Aircraft 1
Make Model Name	TBM 700/TBM 850
Flight Phase	Cruise
Flight Plan	IFR
Aircraft 2
Make Model Name	Gulfstream V / G500 / G550
Flight Phase	Descent
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 3.5
Events
Anomaly	Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

ZLA center controller reported that two aircraft were being stepped down and the higher aircraft descended to an altitude they were not given; leading to a loss of separation.