ZME controller reported issuance of a descent to an aircraft for crossing conflicting traffic. After...

Attributes
ACN	1387364
Time
Date	201609
Local Time Of Day	1201-1800
Place
Locale Reference	ZME.ARTCC
State Reference	TN
Environment
Light	Daylight
Aircraft 1
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 22
Person 2
Function	Enroute Handoff / Assist
Qualification	Air Traffic Control Developmental
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

Narrative:

I turned aircraft X 10 degrees right for a confliction. Aircraft X acknowledged clearance and turned. Shortly later I noticed the turn put aircraft X in conflict with aircraft Y. I asked the R21 controller to take a point out on aircraft X descending to 33000 feet. He said 'point out approved'. I cleared aircraft X to descend and maintain 33000 feet and cleared them direct mem on course. Aircraft X read back the clearance correctly. A moment later I noticed aircraft X turned on course but not descending.I called aircraft X; no reply. I called aircraft X and said 'expedite through FL340'; no reply. I turned aircraft Y to heading 100. Aircraft Y read back clearance. I called aircraft X again and he replied 'yes center'. I said 'aircraft X descend and maintain FL330; I gave you that clearance a couple minutes ago did you not get it?' he said yes we did; but we didn't execute it. After separation was re-established I cleared aircraft Y direct pxv on course. I advised aircraft X of possible pilot deviation and gave him the ZME center watch desk phone number.[suggest] pilots execute clearances issued by ATC. Pilots listen better for transmissions; having to repeat clearances multiple times increases controller workload.

Original NASA ASRS Text

Title: ZME Controller reported issuance of a descent to an aircraft for crossing conflicting traffic. After acknowledging the clearance the aircraft did not descend and was temporarily NORDO.

Narrative: I turned Aircraft X 10 degrees right for a confliction. Aircraft X acknowledged clearance and turned. Shortly later I noticed the turn put Aircraft X in conflict with Aircraft Y. I asked the R21 controller to take a point out on Aircraft X descending to 33000 feet. He said 'point out approved'. I cleared Aircraft X to descend and maintain 33000 feet and cleared them direct MEM on course. Aircraft X read back the clearance correctly. A moment later I noticed Aircraft X turned on course but not descending.I called Aircraft X; no reply. I called Aircraft X and said 'expedite through FL340'; no reply. I turned Aircraft Y to heading 100. Aircraft Y read back clearance. I called Aircraft X again and he replied 'yes Center'. I said 'Aircraft X descend and maintain FL330; I gave you that clearance a couple minutes ago did you not get it?' He said yes we did; but we didn't execute it. After separation was re-established I cleared Aircraft Y direct PXV on course. I advised Aircraft X of possible pilot deviation and gave him the ZME Center watch desk phone number.[Suggest] pilots execute clearances issued by ATC. Pilots listen better for transmissions; having to repeat clearances multiple times increases controller workload.

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.

ZME controller reported issuance of a descent to an aircraft for crossing conflicting traffic. After acknowledging the clearance the aircraft did not descend and was temporarily NORDO.