Date: 201601
Local time of day: 1801-2400
Location: D10.TRACON, TX
Flight conditions: VMC
Light: Daylight
Aircraft: Medium Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B DFW
ATC / advisory: TRACON D10
Second aircraft: Medium Large Transport
Reporter organization: Government
Reporter function: Instructor; Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Distraction; Situational Awareness; Training / Qualification; Communication Breakdown
Second reporter function: First Officer; Pilot Not Flying
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: I was training a CPC (Certified Professional Controller). Aircraft X was issued to descend via the STAR. The STAR level off altitude is 11;000 feet. When I caught they had descended early; they were leaving 7;800 feet. We gave them an immediate descend to 6;000 feet to miss a DFW departure. Aircraft X came within 1;000 feet and 3 miles of Aircraft Y; a DFW departure who was climbing out on the SID. Aircraft X informed us he was issued to descend via the STAR except maintain 6;000 feet from the last controller (ZFW - UKW sector). We issued them descend via the STAR at least twice in initial contact. That clearance from us should have deleted any previous descend via clearance. ZFW (UKW sector) was issuing all of our arrivals amended descend via clearance to make their sequence work. Changing aircraft instructions will mess with the aircraft's FMS. Pilots need to check and recheck their FMS's when [given] different instructions off the STAR. ZFW arrival sector controllers need retraining on how their instructions affect the aircraft flight plan. The ZFW arrival sectors (especially UKW sector) constantly change aircraft speed and or altitudes from what is published on the STAR's. They never coordinate these changes with us. Making those changes need to be coordinated per our LOA. The Feeder controllers are working twice as hard to verify the aircraft are doing what we expect (STAR); and it's putting too much workload on us.


Second narrative: Descending on the JOVEM2 into DFW as assigned by center; we were told to 'descend via' and comply with the speeds. Shortly after; we were told to maintain speed 250kts and cross SILER at 220kts. We were then given further clearance to descend and maintain 6000. We read back the altitude to ATC and confirmed amongst each other. A frequency change to Approach took place.Just prior to crossing SILER and descending thru 7000-7500 ft; Regional Approach (119.87) questioned our altitude. We advised him that the previous controller had assigned us 6000.Poor communication between ATC facilities (center and approach) and flight crew; if in fact a deviation even occurred.The questioning of our altitude by Approach planted the seed that we were at a different altitude other than expected. As far as we knew; we were complying with a clearance assigned that negated the 'descend via' which would have put us at 11000 ft over SILER.


Synopsis: Air carrier flight crew and Controller reported of confusion related to Descend Via clearance. Controller issued descend via the JOVEM2 STAR at least twice. Pilot had received from previous Controller descend via the STAR except maintain 6;000 feet. Controller thought the last clearance he issued was the one the pilot should have done. Pilots were confused and did not do what the last instruction from ATC was.