Narrative:

I was the radar controller on sector R40 and R41. This was a combined sector situation which included working sector 40 traffic (approach control at apc and sts airports (both IFR) and the morning rush of traffic inbound to sfo/sjc/oak from the northwest, over pye VORTAC). I had descended air carrier X to 11000 ft initially to possibly fit him in with the jet arrival route to sfo. As time passed, I perceived that this plan was not going to work, so descended air carrier X to 7000 (propeller/turboprop arrival altitude), but inserted an assigned altitude of 9000 ft in the data block. Traffic was MTR Y on a low altitude IFR training route at 8000 ft (perhaps the reason for entering 9000 in the data block?). MTR Y route was from pye-sgd-ila-bab but was reclred to suu at the pilot's request. I observed MTR Y mode C indicate 082 or 200 ft high. Asked him to verify level at 8000 and quoted air carrier X traffic at 9000. MTR Y verified at 8000 ft then I observed the mode C on air carrier X at 089 or 100 ft low (conflict alert began to activate at this point), and asked him to verify at 9000. Air carrier X replied, 'no, we're out of 8 for 7'. At this point the aircraft were 1.5 mi apart (data reduction readout showed 2.0 mi) and 700 ft vertical separated. I believe I would have caught and prevented the error if the data block on air carrier X had indicated descent to 7000 ft. Contributing factors: 1) workload - these 2 sectors should have been decombined sooner. This error never would have occurred because air carrier X would have not been assigned an altitude lower than 9000 ft (vertical limits of sector 40 are 8000 ft). Sector 40 would have worked MTR Y and descended air carrier X after they had passed. 2) frequency congestion because of sector combination (simultaneous reception of 4 frequencys). 3) flow control kept calling with speed restrictions for sfo arrs (couldn't make up their mind) and then told us to go into holding at pye at the most inconvenient time. 4) no supervisor in area to advise of holding or sector workload. He showed up just in time to see the error. 4) d-ctlr was too busy, with coordination and 3 full bays of strips, to look at radar and possibly catch the error. 5) have had headaches for 2 weeks (possibly from a back or neck strain) and cannot take adequate medication to relieve.

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Original NASA ASRS Text

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

Narrative: I WAS THE RADAR CTLR ON SECTOR R40 AND R41. THIS WAS A COMBINED SECTOR SITUATION WHICH INCLUDED WORKING SECTOR 40 TFC (APCH CTL AT APC AND STS ARPTS (BOTH IFR) AND THE MORNING RUSH OF TFC INBOUND TO SFO/SJC/OAK FROM THE NW, OVER PYE VORTAC). I HAD DSNDED ACR X TO 11000 FT INITIALLY TO POSSIBLY FIT HIM IN WITH THE JET ARR RTE TO SFO. AS TIME PASSED, I PERCEIVED THAT THIS PLAN WAS NOT GOING TO WORK, SO DSNDED ACR X TO 7000 (PROP/TURBOPROP ARR ALT), BUT INSERTED AN ASSIGNED ALT OF 9000 FT IN THE DATA BLOCK. TFC WAS MTR Y ON A LOW ALT IFR TRAINING RTE AT 8000 FT (PERHAPS THE REASON FOR ENTERING 9000 IN THE DATA BLOCK?). MTR Y RTE WAS FROM PYE-SGD-ILA-BAB BUT WAS RECLRED TO SUU AT THE PLT'S REQUEST. I OBSERVED MTR Y MODE C INDICATE 082 OR 200 FT HIGH. ASKED HIM TO VERIFY LEVEL AT 8000 AND QUOTED ACR X TFC AT 9000. MTR Y VERIFIED AT 8000 FT THEN I OBSERVED THE MODE C ON ACR X AT 089 OR 100 FT LOW (CONFLICT ALERT BEGAN TO ACTIVATE AT THIS POINT), AND ASKED HIM TO VERIFY AT 9000. ACR X REPLIED, 'NO, WE'RE OUT OF 8 FOR 7'. AT THIS POINT THE ACFT WERE 1.5 MI APART (DATA REDUCTION READOUT SHOWED 2.0 MI) AND 700 FT VERT SEPARATED. I BELIEVE I WOULD HAVE CAUGHT AND PREVENTED THE ERROR IF THE DATA BLOCK ON ACR X HAD INDICATED DSCNT TO 7000 FT. CONTRIBUTING FACTORS: 1) WORKLOAD - THESE 2 SECTORS SHOULD HAVE BEEN DECOMBINED SOONER. THIS ERROR NEVER WOULD HAVE OCCURRED BECAUSE ACR X WOULD HAVE NOT BEEN ASSIGNED AN ALT LOWER THAN 9000 FT (VERT LIMITS OF SECTOR 40 ARE 8000 FT). SECTOR 40 WOULD HAVE WORKED MTR Y AND DSNDED ACR X AFTER THEY HAD PASSED. 2) FREQ CONGESTION BECAUSE OF SECTOR COMBINATION (SIMULTANEOUS RECEPTION OF 4 FREQS). 3) FLOW CTL KEPT CALLING WITH SPD RESTRICTIONS FOR SFO ARRS (COULDN'T MAKE UP THEIR MIND) AND THEN TOLD US TO GO INTO HOLDING AT PYE AT THE MOST INCONVENIENT TIME. 4) NO SUPVR IN AREA TO ADVISE OF HOLDING OR SECTOR WORKLOAD. HE SHOWED UP JUST IN TIME TO SEE THE ERROR. 4) D-CTLR WAS TOO BUSY, WITH COORD AND 3 FULL BAYS OF STRIPS, TO LOOK AT RADAR AND POSSIBLY CATCH THE ERROR. 5) HAVE HAD HEADACHES FOR 2 WKS (POSSIBLY FROM A BACK OR NECK STRAIN) AND CANNOT TAKE ADEQUATE MEDICATION TO RELIEVE.

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.