Narrative:

This event involved 2 aircraft in oceanic non-radar airspace. #1 aircraft was air carrier X (RNAV) 2000N/6000W dct tooms. Already active and in my sector at FL310 when I assumed sector responsibility. #2 aircraft was air carrier Y a san juan departure vermo dct kraft. I authorized air carrier Y to climb to FL280 while I checked crossing times with air carrier X at FL310. Sectors 2,4,6 were combined at my position and it was very busy. I computed crossing time based on a handwritten bdy estimate in block 21 of FAA 7230.19. Initially my computations indicated an ample 22 min. I then cleared air carrier Y to FL310. I was then relieved for a break. In the process of going back to resume the sector (well after the actual crossing) the adjacent facility sector controller called to question the crossing time. We then rechked the actual progress over tooms and found that the bdy estimate in block 21 was in error. The origin of this estimate is not known to me. When I originally computed crossing times the sector was very busy, I did not have time to doublechk that estimate. This caused the aircraft involved to cross within 5 to 7 mins of each other. At the point of crossing both air carrier X and air carrier Y were off radar. Air carrier X was never in radio communication with us. In addition to the already heavy workload, the facility was experiencing landline problems that had eliminated communication and coordination with 3 adjacent ARTCC's and 3 approach controls. I believe the sectors being combined at a time when it is frequently split, plus landline communications failure with adjacent facilities, and the erroneous boundary estimate (possibly written by a previous controller) added up to a workload condition in which I was unable to verify and doublechk.

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Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: THIS EVENT INVOLVED 2 ACFT IN OCEANIC NON-RADAR AIRSPACE. #1 ACFT WAS ACR X (RNAV) 2000N/6000W DCT TOOMS. ALREADY ACTIVE AND IN MY SECTOR AT FL310 WHEN I ASSUMED SECTOR RESPONSIBILITY. #2 ACFT WAS ACR Y A SAN JUAN DEP VERMO DCT KRAFT. I AUTHORIZED ACR Y TO CLB TO FL280 WHILE I CHKED XING TIMES WITH ACR X AT FL310. SECTORS 2,4,6 WERE COMBINED AT MY POS AND IT WAS VERY BUSY. I COMPUTED XING TIME BASED ON A HANDWRITTEN BDY ESTIMATE IN BLOCK 21 OF FAA 7230.19. INITIALLY MY COMPUTATIONS INDICATED AN AMPLE 22 MIN. I THEN CLRED ACR Y TO FL310. I WAS THEN RELIEVED FOR A BREAK. IN THE PROCESS OF GOING BACK TO RESUME THE SECTOR (WELL AFTER THE ACTUAL XING) THE ADJACENT FACILITY SECTOR CTLR CALLED TO QUESTION THE XING TIME. WE THEN RECHKED THE ACTUAL PROGRESS OVER TOOMS AND FOUND THAT THE BDY ESTIMATE IN BLOCK 21 WAS IN ERROR. THE ORIGIN OF THIS ESTIMATE IS NOT KNOWN TO ME. WHEN I ORIGINALLY COMPUTED XING TIMES THE SECTOR WAS VERY BUSY, I DID NOT HAVE TIME TO DOUBLECHK THAT ESTIMATE. THIS CAUSED THE ACFT INVOLVED TO CROSS WITHIN 5 TO 7 MINS OF EACH OTHER. AT THE POINT OF XING BOTH ACR X AND ACR Y WERE OFF RADAR. ACR X WAS NEVER IN RADIO COM WITH US. IN ADDITION TO THE ALREADY HVY WORKLOAD, THE FACILITY WAS EXPERIENCING LANDLINE PROBLEMS THAT HAD ELIMINATED COM AND COORD WITH 3 ADJACENT ARTCC'S AND 3 APCH CTLS. I BELIEVE THE SECTORS BEING COMBINED AT A TIME WHEN IT IS FREQUENTLY SPLIT, PLUS LANDLINE COMS FAILURE WITH ADJACENT FACILITIES, AND THE ERRONEOUS BOUNDARY ESTIMATE (POSSIBLY WRITTEN BY A PREVIOUS CTLR) ADDED UP TO A WORKLOAD CONDITION IN WHICH I WAS UNABLE TO VERIFY AND DOUBLECHK.

Data retrieved from NASA's ASRS site as of July 2007 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.