ZJX controller describes a loss of separation between two aircraft. Controller attempts to use speed...

Narrative:

We had moved to midnight configuration with all sectors combined at sector 76. I had been talking non-stop for about a half hour to forty-five minutes and things were finally slowing down a little; though not unusually busy for that time of night. Rides were light turbulence at most altitudes with a few reports of occasional moderate chop. I made a plan for spacing of three mco arrivals that I had; and had plenty of time to make my plan work. Aircraft Y was number one in sequence and was assigned M80+ and transition to 310 kts; aircraft X was assigned M82 (to run past the 3rd mco arrival that was not a factor) and then was told to transition to 300 kts. Assigned speeds were working for all aircraft with a slight overtake with aircraft X catching aircraft Y and I issued crossing restrictions to all three aircraft. I was monitoring the speeds in the descent and noticed that aircraft Y slowed by another 10 kts instead of increasing as I expected; and I asked 'aircraft Y are you going to be able to maintain the assigned 310 kts?' to which they responded 'negative; we're slowing to 270 kts'. There was now a significant overtake; so I told aircraft Y to amend altitude and maintain FL270; and it was read back correctly. I then told aircraft X to slow to 260 kts and turn 20 degrees left. Aircraft Y comes back and says they were already through FL270 when the clearance was issued and they were descending to FL260. It appeared as though separation was lost before the turn of aircraft X took effect. I believe fatigue was a direct cause of this event; I was about one minute too late in turning aircraft X to prevent a loss; and was about three minutes to late in ensuring that assigned speeds were indeed working. Another contributing factor however was that aircraft Y did not comply with the speed that was assigned and did not inform me of that decision.

Original NASA ASRS Text

Title: ZJX Controller describes a loss of separation between two aircraft. Controller attempts to use speed control; but first aircraft slows while second aircraft has its speed as instructed. Loss of separation occurs and Controller blames fatigue but doesn't expand on that.

Narrative: We had moved to midnight configuration with all sectors combined at sector 76. I had been talking non-stop for about a half hour to forty-five minutes and things were finally slowing down a little; though not unusually busy for that time of night. Rides were light turbulence at most altitudes with a few reports of occasional moderate chop. I made a plan for spacing of three MCO arrivals that I had; and had plenty of time to make my plan work. Aircraft Y was number one in sequence and was assigned M80+ and transition to 310 kts; Aircraft X was assigned M82 (to run past the 3rd MCO arrival that was not a factor) and then was told to transition to 300 kts. Assigned speeds were working for all aircraft with a slight overtake with Aircraft X catching Aircraft Y and I issued crossing restrictions to all three aircraft. I was monitoring the speeds in the descent and noticed that Aircraft Y slowed by another 10 kts instead of increasing as I expected; and I asked 'Aircraft Y are you going to be able to maintain the assigned 310 kts?' to which they responded 'Negative; we're slowing to 270 kts'. There was now a significant overtake; so I told Aircraft Y to amend altitude and maintain FL270; and it was read back correctly. I then told Aircraft X to slow to 260 kts and turn 20 degrees left. Aircraft Y comes back and says they were already through FL270 when the clearance was issued and they were descending to FL260. It appeared as though separation was lost before the turn of Aircraft X took effect. I believe fatigue was a direct cause of this event; I was about one minute too late in turning Aircraft X to prevent a loss; and was about three minutes to late in ensuring that assigned speeds were indeed working. Another contributing factor however was that Aircraft Y did not comply with the speed that was assigned and did not inform me of that decision.

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	1240954
Time
Date	201502
Local Time Of Day	0001-0600
Place
Locale Reference	ZJX.ARTCC
State Reference	FL
Environment
Light	Night
Aircraft 1
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Aircraft 2
Make Model Name	Large Transport
Operating Under FAR Part	Part 121
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) 2.75
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence

ZJX controller describes a loss of separation between two aircraft. Controller attempts to use speed control; but first aircraft slows while second aircraft has its speed as instructed. Loss of separation occurs and controller blames fatigue but doesn't expand on that.