Narrative:

On 11/90 the NAS computer failed at oak ARTCC. After the failure the transition to darc was made. The transition was made in a smooth and effective manner with all aircraft identify maintained. About 1/2 hour into darc operation we were told to return to NAS. We began this process and had been in NAS for about 4-5 mins when NAS failed for the second time. When we tried to return to darc we had no control of the system. After several mins of struggling we were told that the darc was now operational. When we finally received control of darc there was no data stored on any aircraft. At this time due to the amount of traffic in several sectors, aircraft identify was lost on several aircraft. I was assigned sector D33 and H33 during this period. I saw 2 heavy jets come with 2 1/2 mi of each other at inyoe at FL350. Several aircraft entered other oak sectors west/O handoffs. I personally made at lest 3 handoffs to slc and ZLA. The only information I had was aircraft identify and altitude. The major cause of these situations was the loss of data when we attempted to return to darc the second time. During darc no data was passed to other facs, and as far as I know, there was no flow control procedures instituted. The results were loss of sep, system deviations, aircraft being held west/O prior warning and loss of aircraft idents.

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Original NASA ASRS Text

Title: THE NAS COMPUTER FAILED FOR THE SECOND TIME AND ON CHANGEOVER TO THE DARC SYSTEM NO ACFT DATA WAS AVAILABLE FOR CTLR'S USE.

Narrative: ON 11/90 THE NAS COMPUTER FAILED AT OAK ARTCC. AFTER THE FAILURE THE TRANSITION TO DARC WAS MADE. THE TRANSITION WAS MADE IN A SMOOTH AND EFFECTIVE MANNER WITH ALL ACFT IDENT MAINTAINED. ABOUT 1/2 HR INTO DARC OPERATION WE WERE TOLD TO RETURN TO NAS. WE BEGAN THIS PROCESS AND HAD BEEN IN NAS FOR ABOUT 4-5 MINS WHEN NAS FAILED FOR THE SECOND TIME. WHEN WE TRIED TO RETURN TO DARC WE HAD NO CTL OF THE SYS. AFTER SEVERAL MINS OF STRUGGLING WE WERE TOLD THAT THE DARC WAS NOW OPERATIONAL. WHEN WE FINALLY RECEIVED CTL OF DARC THERE WAS NO DATA STORED ON ANY ACFT. AT THIS TIME DUE TO THE AMOUNT OF TFC IN SEVERAL SECTORS, ACFT IDENT WAS LOST ON SEVERAL ACFT. I WAS ASSIGNED SECTOR D33 AND H33 DURING THIS PERIOD. I SAW 2 HVY JETS COME WITH 2 1/2 MI OF EACH OTHER AT INYOE AT FL350. SEVERAL ACFT ENTERED OTHER OAK SECTORS W/O HDOFS. I PERSONALLY MADE AT LEST 3 HDOFS TO SLC AND ZLA. THE ONLY INFO I HAD WAS ACFT IDENT AND ALT. THE MAJOR CAUSE OF THESE SITUATIONS WAS THE LOSS OF DATA WHEN WE ATTEMPTED TO RETURN TO DARC THE SECOND TIME. DURING DARC NO DATA WAS PASSED TO OTHER FACS, AND AS FAR AS I KNOW, THERE WAS NO FLOW CTL PROCS INSTITUTED. THE RESULTS WERE LOSS OF SEP, SYS DEVIATIONS, ACFT BEING HELD W/O PRIOR WARNING AND LOSS OF ACFT IDENTS.

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.