Narrative:

I was working west arrival/departure combined with moderate traffic. I was trying to establish radio contact with an aircraft that had been handed off. As I was visually scanning my traffic, I noticed a VFR symbol appear about 12 mi southwest of the airport heading north and I had large transport X runway heading off runway 25L climbing to 11000'. Initially the VFR had no altitude readout. As the targets were getting closer the VFR showed an altitude of 4400' with large transport X climbing out of 3700'. I issued a safety alert to large transport X and advised him to maintain 4000'. I then turned air carrier to heading 240 degrees. This occurred in the span of 3-4 sweeps of the radar. I don't think much more could have been done. The VFR seem to come out of a blind spot or could have been in the VFR practice area that starts approximately where the incident occurred and may have been in a maximum climb. Callback conversation with reporter acn 91508 revealed the following: the air carrier large transport flight crew filed an official near midair collision report with their company. Reporter was not sure how close the 2 aircraft did come to each other, but did hear from the captain of the large transport that the F/a had reported the small aircraft as diving from just above the large transport to out of sight below. Reporter characterized the proximity as 'very close.' reporter was given a letter of appreciation from his facility for his timely traffic alert. The ntap of the incident showed that the large transport did stop its climb below the small aircraft. If the small aircraft had not dived, the sep would have been better than it was. Supplemental information from acn 91534: received traffic advisory from departure control of traffic at 9 O'clock, 1 mi northbound at 4400', and told to maintain 4000'. We were climbing through 4000' at time and I pushed nose over but momentum carried us to 4250' before descending back to 4000'. Was then told that traffic had made an abrupt descent to 3500'. Was issued clearance to climb to 9000' with no further incidents. F/a in left rear cabin observed a single engine, low wing, white with red trim aircraft inverted and diving. He estimated the aircraft to be within 1/4 mi of us. I appreciate the departure controller issuing the advisory, but think his clearance for us to maintain 4000' at that point was an error. We were climbing through 4000' at 1500 FPM and that action put us almost level with the target's altitude before we could reverse the ascent and level off.

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Original NASA ASRS Text

Title: DURING CLIMBOUT, ACR LGT NEARLY COLLIDED WITH VFR UNK-SMA.

Narrative: I WAS WORKING W ARR/DEP COMBINED WITH MODERATE TFC. I WAS TRYING TO ESTABLISH RADIO CONTACT WITH AN ACFT THAT HAD BEEN HANDED OFF. AS I WAS VISUALLY SCANNING MY TFC, I NOTICED A VFR SYMBOL APPEAR ABOUT 12 MI SW OF THE ARPT HDG N AND I HAD LGT X RWY HDG OFF RWY 25L CLBING TO 11000'. INITIALLY THE VFR HAD NO ALT READOUT. AS THE TARGETS WERE GETTING CLOSER THE VFR SHOWED AN ALT OF 4400' WITH LGT X CLBING OUT OF 3700'. I ISSUED A SAFETY ALERT TO LGT X AND ADVISED HIM TO MAINTAIN 4000'. I THEN TURNED ACR TO HDG 240 DEGS. THIS OCCURRED IN THE SPAN OF 3-4 SWEEPS OF THE RADAR. I DON'T THINK MUCH MORE COULD HAVE BEEN DONE. THE VFR SEEM TO COME OUT OF A BLIND SPOT OR COULD HAVE BEEN IN THE VFR PRACTICE AREA THAT STARTS APPROX WHERE THE INCIDENT OCCURRED AND MAY HAVE BEEN IN A MAX CLB. CALLBACK CONVERSATION WITH RPTR ACN 91508 REVEALED THE FOLLOWING: THE ACR LGT FLT CREW FILED AN OFFICIAL NMAC RPT WITH THEIR COMPANY. RPTR WAS NOT SURE HOW CLOSE THE 2 ACFT DID COME TO EACH OTHER, BUT DID HEAR FROM THE CAPT OF THE LGT THAT THE F/A HAD RPTED THE SMA AS DIVING FROM JUST ABOVE THE LGT TO OUT OF SIGHT BELOW. RPTR CHARACTERIZED THE PROX AS 'VERY CLOSE.' RPTR WAS GIVEN A LETTER OF APPRECIATION FROM HIS FAC FOR HIS TIMELY TFC ALERT. THE NTAP OF THE INCIDENT SHOWED THAT THE LGT DID STOP ITS CLB BELOW THE SMA. IF THE SMA HAD NOT DIVED, THE SEP WOULD HAVE BEEN BETTER THAN IT WAS. SUPPLEMENTAL INFO FROM ACN 91534: RECEIVED TFC ADVISORY FROM DEP CTL OF TFC AT 9 O'CLOCK, 1 MI NBOUND AT 4400', AND TOLD TO MAINTAIN 4000'. WE WERE CLBING THROUGH 4000' AT TIME AND I PUSHED NOSE OVER BUT MOMENTUM CARRIED US TO 4250' BEFORE DSNDING BACK TO 4000'. WAS THEN TOLD THAT TFC HAD MADE AN ABRUPT DSCNT TO 3500'. WAS ISSUED CLRNC TO CLB TO 9000' WITH NO FURTHER INCIDENTS. F/A IN LEFT REAR CABIN OBSERVED A SINGLE ENG, LOW WING, WHITE WITH RED TRIM ACFT INVERTED AND DIVING. HE ESTIMATED THE ACFT TO BE WITHIN 1/4 MI OF US. I APPRECIATE THE DEP CTLR ISSUING THE ADVISORY, BUT THINK HIS CLRNC FOR US TO MAINTAIN 4000' AT THAT POINT WAS AN ERROR. WE WERE CLBING THROUGH 4000' AT 1500 FPM AND THAT ACTION PUT US ALMOST LEVEL WITH THE TARGET'S ALT BEFORE WE COULD REVERSE THE ASCENT AND LEVEL OFF.

Data retrieved from NASA's ASRS site as of August 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.