Narrative:

At about XA15 local, during a peak oceanic traffic period, ZOA suffered a complete power outage affecting all automation system, radar system, and radio communications. This left the entire facility without any practical method of providing ATC service. Radar and VHF communications were restored after about 35 mins, however oceanic automations remained out for about 2 hours during the busiest time of day for traffic. There was no advanced indication of a problem. While departures were held, traffic was sufficient to create many safety related concerns. Since oceanic communications (inbound messages) are linked to the automation, position reports, clearance readbacks and various control messages were delayed and greatly affected our ability to perform even basic ATC services. There is no true backup system, and even if one were in place, it is highly likely that it, too, would have failed. Supplemental information from acn 312517: ZOA experienced complete loss of radio and radar coverage. Just after establishing contact with bay approach, we observed traffic converging from our left, apparently at our altitude. Consulted HSI for TCASII information and confirmed same altitude. Almost immediately, TCASII called 'traffic,' then issued a 'climb' RA. Climbed in response to RA and advised bay approach. At about FL356 TCASII advised 'monitor vertical speed' and at about FL358 TCASII advised 'clear of conflict.' descended to FL350 and advised bay approach. Supplemental information from acn 313116: air carrier Y had been in oakland's airspace for 10-15 mins and we were aware that center was not responding to radio xmissions on our assigned frequency, 132.8. The event began as a TCASII TA at our 2 O'clock position, showing same altitude. We acquired visual contact almost simultaneously. The actual intruder, a B757, was outside the range of the TCASII display, so only the relative altitude graphics showed. I would estimate his range at this time as 6-7 mi, converging from our 2 O'clock at roughly a 45 degree angle. We watched him for a few seconds and immediately realized that although there was no threat of collision, we would pass very close behind him. At the same time TCASII ordered a 'descend' RA which was followed by 'monitor vertical speed' during the descent. 'Clear of conflict' was announced at 34200 ft and we returned to FL350. About this time ZOA was regaining radio communications. We advised the controller of the conflict and the ensuing evasive maneuver. He advised us at that time that center radar was down and asked us for our position and to verify that we were at FL350. Supplemental information from acn 312405: during power outage at ZOA on aug/wed/95, several aircraft in sector above FL240 over fresno general area. Aircraft exited my airspace without handoffs and became TCASII conflictions in adjacent sectors, facilities. No radio or radar available for 20-40 mins.

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Original NASA ASRS Text

Title: ATC EQUIP PROB PWR FAILED RADAR COM FAILED. ACR X TCASII TA RA HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: AT ABOUT XA15 LCL, DURING A PEAK OCEANIC TFC PERIOD, ZOA SUFFERED A COMPLETE PWR OUTAGE AFFECTING ALL AUTOMATION SYS, RADAR SYS, AND RADIO COMS. THIS LEFT THE ENTIRE FACILITY WITHOUT ANY PRACTICAL METHOD OF PROVIDING ATC SVC. RADAR AND VHF COMS WERE RESTORED AFTER ABOUT 35 MINS, HOWEVER OCEANIC AUTOMATIONS REMAINED OUT FOR ABOUT 2 HRS DURING THE BUSIEST TIME OF DAY FOR TFC. THERE WAS NO ADVANCED INDICATION OF A PROB. WHILE DEPS WERE HELD, TFC WAS SUFFICIENT TO CREATE MANY SAFETY RELATED CONCERNS. SINCE OCEANIC COMS (INBOUND MESSAGES) ARE LINKED TO THE AUTOMATION, POS RPTS, CLRNC READBACKS AND VARIOUS CTL MESSAGES WERE DELAYED AND GREATLY AFFECTED OUR ABILITY TO PERFORM EVEN BASIC ATC SVCS. THERE IS NO TRUE BACKUP SYS, AND EVEN IF ONE WERE IN PLACE, IT IS HIGHLY LIKELY THAT IT, TOO, WOULD HAVE FAILED. SUPPLEMENTAL INFO FROM ACN 312517: ZOA EXPERIENCED COMPLETE LOSS OF RADIO AND RADAR COVERAGE. JUST AFTER ESTABLISHING CONTACT WITH BAY APCH, WE OBSERVED TFC CONVERGING FROM OUR L, APPARENTLY AT OUR ALT. CONSULTED HSI FOR TCASII INFO AND CONFIRMED SAME ALT. ALMOST IMMEDIATELY, TCASII CALLED 'TFC,' THEN ISSUED A 'CLB' RA. CLBED IN RESPONSE TO RA AND ADVISED BAY APCH. AT ABOUT FL356 TCASII ADVISED 'MONITOR VERT SPD' AND AT ABOUT FL358 TCASII ADVISED 'CLR OF CONFLICT.' DSNDED TO FL350 AND ADVISED BAY APCH. SUPPLEMENTAL INFO FROM ACN 313116: ACR Y HAD BEEN IN OAKLAND'S AIRSPACE FOR 10-15 MINS AND WE WERE AWARE THAT CTR WAS NOT RESPONDING TO RADIO XMISSIONS ON OUR ASSIGNED FREQ, 132.8. THE EVENT BEGAN AS A TCASII TA AT OUR 2 O'CLOCK POS, SHOWING SAME ALT. WE ACQUIRED VISUAL CONTACT ALMOST SIMULTANEOUSLY. THE ACTUAL INTRUDER, A B757, WAS OUTSIDE THE RANGE OF THE TCASII DISPLAY, SO ONLY THE RELATIVE ALT GRAPHICS SHOWED. I WOULD ESTIMATE HIS RANGE AT THIS TIME AS 6-7 MI, CONVERGING FROM OUR 2 O'CLOCK AT ROUGHLY A 45 DEG ANGLE. WE WATCHED HIM FOR A FEW SECONDS AND IMMEDIATELY REALIZED THAT ALTHOUGH THERE WAS NO THREAT OF COLLISION, WE WOULD PASS VERY CLOSE BEHIND HIM. AT THE SAME TIME TCASII ORDERED A 'DSND' RA WHICH WAS FOLLOWED BY 'MONITOR VERT SPD' DURING THE DSCNT. 'CLR OF CONFLICT' WAS ANNOUNCED AT 34200 FT AND WE RETURNED TO FL350. ABOUT THIS TIME ZOA WAS REGAINING RADIO COMS. WE ADVISED THE CTLR OF THE CONFLICT AND THE ENSUING EVASIVE MANEUVER. HE ADVISED US AT THAT TIME THAT CTR RADAR WAS DOWN AND ASKED US FOR OUR POS AND TO VERIFY THAT WE WERE AT FL350. SUPPLEMENTAL INFO FROM ACN 312405: DURING PWR OUTAGE AT ZOA ON AUG/WED/95, SEVERAL ACFT IN SECTOR ABOVE FL240 OVER FRESNO GENERAL AREA. ACFT EXITED MY AIRSPACE WITHOUT HDOFS AND BECAME TCASII CONFLICTIONS IN ADJACENT SECTORS, FACILITIES. NO RADIO OR RADAR AVAILABLE FOR 20-40 MINS.

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.