Narrative:

I was on the return flight from O17 using flight following from sac approach. I checked in level at 4500 ft approximately 4 mi southeast of smf. The controller called 'traffic, a B-737, 3 mi, climb out of 3000 ft at your 3 O'clock.' I responded, 'traffic in sight.' the controller then became busy calling traffic to other pilots for about 90 seconds. In this time, the B-737 continued to climb directly at me. Although I had the B-737 in sight at all times, I made a judgement that if I held my altitude, at the rate it was climbing, it would result in a serious collision conflict -- at the least I would be involved in its wake turbulence. It appeared that the B-737 would climb over me, but only by a few ft. It was moving so fast that I had to act immediately or the results could have been disastrous. I decided to descend. As soon as the controller stopped talking I reported 'descending to avoid B-737.' I descended to 3700 ft MSL as the B-737 passed 1000 ft over me and about 500 ft behind me. The controller responded 'you were instructed to maintain 4500 ft.' (I don't believe my altitude was ever restr.) if I had heard that the B-737 was restr at 3000 ft I would not have been as worried, but the controller had said, B-737 'climbing out of 3000 ft.' this indicated to me an unrestr climb. I responded. 'That looked too close to me.' the B-737 pilot reported, 'the tomahawk descended into our altitude.' the controller responded, 'roger.' I returned to 4500 ft and was handed off to the next controller without comment. It has always been my understanding that the see and avoid rule takes precedence over any ATC directive if the safety of the flight is in danger (91.3). In this case it was my judgement that it was. I believe the controller was in error in 2 ways. 1) he did not maintain separation between myself and the B-737. 2) he thought I was restr at 4500 ft although if I had held that altitude it could have been fatal. Callback conversation with reporter revealed the following information: reporter did not have any additional information on this incident, not having heard from the FAA or ATC. When asked if it was possible that her traffic watch considerations could have 'blanked out' her reception of what was being said to other aircraft on the frequency, she responded, 'that's a possibility.' when asked if the other aircraft, in its climb nearby her aircraft, appeared to have reacted to its TCASII off her transponder, she replied, 'oh, definitely.'

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Original NASA ASRS Text

Title: POTENTIAL CONFLICT IN PROX OF ARSA CLASS C AIRSPACE. NON ADHERENCE TO ATC INSTRUCTION.

Narrative: I WAS ON THE RETURN FLT FROM O17 USING FLT FOLLOWING FROM SAC APCH. I CHKED IN LEVEL AT 4500 FT APPROX 4 MI SE OF SMF. THE CTLR CALLED 'TFC, A B-737, 3 MI, CLBOUT OF 3000 FT AT YOUR 3 O'CLOCK.' I RESPONDED, 'TFC IN SIGHT.' THE CTLR THEN BECAME BUSY CALLING TFC TO OTHER PLTS FOR ABOUT 90 SECONDS. IN THIS TIME, THE B-737 CONTINUED TO CLB DIRECTLY AT ME. ALTHOUGH I HAD THE B-737 IN SIGHT AT ALL TIMES, I MADE A JUDGEMENT THAT IF I HELD MY ALT, AT THE RATE IT WAS CLBING, IT WOULD RESULT IN A SERIOUS COLLISION CONFLICT -- AT THE LEAST I WOULD BE INVOLVED IN ITS WAKE TURB. IT APPEARED THAT THE B-737 WOULD CLB OVER ME, BUT ONLY BY A FEW FT. IT WAS MOVING SO FAST THAT I HAD TO ACT IMMEDIATELY OR THE RESULTS COULD HAVE BEEN DISASTROUS. I DECIDED TO DSND. AS SOON AS THE CTLR STOPPED TALKING I RPTED 'DSNDING TO AVOID B-737.' I DSNDED TO 3700 FT MSL AS THE B-737 PASSED 1000 FT OVER ME AND ABOUT 500 FT BEHIND ME. THE CTLR RESPONDED 'YOU WERE INSTRUCTED TO MAINTAIN 4500 FT.' (I DON'T BELIEVE MY ALT WAS EVER RESTR.) IF I HAD HEARD THAT THE B-737 WAS RESTR AT 3000 FT I WOULD NOT HAVE BEEN AS WORRIED, BUT THE CTLR HAD SAID, B-737 'CLBING OUT OF 3000 FT.' THIS INDICATED TO ME AN UNRESTR CLB. I RESPONDED. 'THAT LOOKED TOO CLOSE TO ME.' THE B-737 PLT RPTED, 'THE TOMAHAWK DSNDED INTO OUR ALT.' THE CTLR RESPONDED, 'ROGER.' I RETURNED TO 4500 FT AND WAS HANDED OFF TO THE NEXT CTLR WITHOUT COMMENT. IT HAS ALWAYS BEEN MY UNDERSTANDING THAT THE SEE AND AVOID RULE TAKES PRECEDENCE OVER ANY ATC DIRECTIVE IF THE SAFETY OF THE FLT IS IN DANGER (91.3). IN THIS CASE IT WAS MY JUDGEMENT THAT IT WAS. I BELIEVE THE CTLR WAS IN ERROR IN 2 WAYS. 1) HE DID NOT MAINTAIN SEPARATION BTWN MYSELF AND THE B-737. 2) HE THOUGHT I WAS RESTR AT 4500 FT ALTHOUGH IF I HAD HELD THAT ALT IT COULD HAVE BEEN FATAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR DID NOT HAVE ANY ADDITIONAL INFO ON THIS INCIDENT, NOT HAVING HEARD FROM THE FAA OR ATC. WHEN ASKED IF IT WAS POSSIBLE THAT HER TFC WATCH CONSIDERATIONS COULD HAVE 'BLANKED OUT' HER RECEPTION OF WHAT WAS BEING SAID TO OTHER ACFT ON THE FREQ, SHE RESPONDED, 'THAT'S A POSSIBILITY.' WHEN ASKED IF THE OTHER ACFT, IN ITS CLB NEARBY HER ACFT, APPEARED TO HAVE REACTED TO ITS TCASII OFF HER XPONDER, SHE REPLIED, 'OH, DEFINITELY.'

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.