ZAB controller describes climbing an aircraft to its requested altitude; then after 10 minutes the p...

Attributes
ACN	1218161
Time
Date	201411
Local Time Of Day	1801-2400
Place
Locale Reference	ZAB.ARTCC
State Reference	NM
Environment
Light	Night
Aircraft 1
Make Model Name	Medium Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Aircraft 2
Make Model Name	Medium Large Transport Low Wing 2 Turbojet Eng
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 14
Person 2
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 6500 Flight Crew Type 2500
Events
Anomaly	Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance

Narrative:

Aircraft X entered my airspace westbound at FL400. The pilot asked for FL430 at some point in my airspace and I told him there was a recent report north of his position of continuous light chop. Aircraft X asked for the winds at FL430 and I asked the other aircraft and he gave the winds. After a couple minutes; aircraft X requested a climb to FL430 and there was no traffic; so I gave a clearance to climb. Aircraft X was level for several minutes and I had aircraft Y enter my airspace at FL410 eastbound. Aircraft X and aircraft Y were on opposite courses and head on; separated by altitude. When they were about 10 miles apart; aircraft X advised that the temperature was too warm and needed a descent; he also advised that he saw the traffic at FL410. I told the pilot I would get him lower as soon as they passed and I had separation. Shortly after that; aircraft X advised he needed a turn and lower. I issued a 30 degree right turn and told the pilot I would have lower shortly. Aircraft X advised that they could not keep altitude and had started down and needed lower. At this point; the aircraft had passed but I did not have standard separation. I saw in the data block aircraft X showed FL427 and they looked about 3 miles apart and I advised lower would be available shortly. The next radar hit showed the altitude at FL424 and descending. I soon had separation and descended aircraft X to FL400 and they continued the flight. I advised the controller in charge that separation was lost on the 2 aircraft due to warm air at FL430.

Original NASA ASRS Text

Title: ZAB Controller describes climbing an aircraft to its requested altitude; then after 10 minutes the pilot advises the CPC that they need to descend. CPC tells pilot in a few minutes for opposite direction traffic; pilot descends anyway causing a loss of separation.

Narrative: Aircraft X entered my airspace westbound at FL400. The pilot asked for FL430 at some point in my airspace and I told him there was a recent report north of his position of continuous light chop. Aircraft X asked for the winds at FL430 and I asked the other aircraft and he gave the winds. After a couple minutes; Aircraft X requested a climb to FL430 and there was no traffic; so I gave a clearance to climb. Aircraft X was level for several minutes and I had Aircraft Y enter my airspace at FL410 eastbound. Aircraft X and Aircraft Y were on opposite courses and head on; separated by altitude. When they were about 10 miles apart; Aircraft X advised that the temperature was too warm and needed a descent; he also advised that he saw the traffic at FL410. I told the pilot I would get him lower as soon as they passed and I had separation. Shortly after that; Aircraft X advised he needed a turn and lower. I issued a 30 degree right turn and told the pilot I would have lower shortly. Aircraft X advised that they could not keep altitude and had started down and needed lower. At this point; the aircraft had passed but I did not have standard separation. I saw in the data block Aircraft X showed FL427 and they looked about 3 miles apart and I advised lower would be available shortly. The next radar hit showed the altitude at FL424 and descending. I soon had separation and descended Aircraft X to FL400 and they continued the flight. I advised the CIC that separation was lost on the 2 aircraft due to warm air at FL430.

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.

ZAB controller describes climbing an aircraft to its requested altitude; then after 10 minutes the pilot advises the cpc that they need to descend. Cpc tells pilot in a few minutes for opposite direction traffic; pilot descends anyway causing a loss of separation.