Narrative:

Took the aircraft out to test a new wastegate installed on right engine. Was vectored out of class C airspace to north and radar service terminated. Climbed to 12500 ft and set up for cruise on 320 degree heading. Gso was landing runway 32 so decided to make descent towards southwest quadrant to re-enter class C. Was on 200 degree heading and began descent and tuned ATIS for rechk of current information. Copied ATIS, adjusted VOR CDI and looked out left window to see a silver and red B737 pass underneath on a wnw heading. Switched to departure and no one talking there, tried center and he was pointing out additional traffic to someone. Went on and contacted approach for return to gso. The 737 had probably just switched to center during climb out of gso, don't know if they had discussed my target on 1200 mode C or not, but my descent may have surprised them. I should have brought a copilot along to watch or tune radios while I checked the engine and naved aircraft. Should have tuned radios while in level flight and then started descent. Should have been looking more carefully for traffic. He came from below left, clbouts coming towards you are small and not moving against the backgnd of cities and farms below. Should have insisted on continuing flight following with approach even though I was climbing out and leaving class C. Next time I will at least take along an observer to look out while I adjust and check things. Will also stay in radar with someone while that close in to a major airport.

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Original NASA ASRS Text

Title: NMAC BTWN AN SMT DSNDING AND AN MLG CLBING OUT JUST OUTSIDE OF CLASS C AIRSPACE.

Narrative: TOOK THE ACFT OUT TO TEST A NEW WASTEGATE INSTALLED ON R ENG. WAS VECTORED OUT OF CLASS C AIRSPACE TO N AND RADAR SVC TERMINATED. CLBED TO 12500 FT AND SET UP FOR CRUISE ON 320 DEG HDG. GSO WAS LNDG RWY 32 SO DECIDED TO MAKE DSCNT TOWARDS SW QUADRANT TO RE-ENTER CLASS C. WAS ON 200 DEG HDG AND BEGAN DSCNT AND TUNED ATIS FOR RECHK OF CURRENT INFO. COPIED ATIS, ADJUSTED VOR CDI AND LOOKED OUT L WINDOW TO SEE A SILVER AND RED B737 PASS UNDERNEATH ON A WNW HDG. SWITCHED TO DEP AND NO ONE TALKING THERE, TRIED CTR AND HE WAS POINTING OUT ADDITIONAL TFC TO SOMEONE. WENT ON AND CONTACTED APCH FOR RETURN TO GSO. THE 737 HAD PROBABLY JUST SWITCHED TO CTR DURING CLB OUT OF GSO, DON'T KNOW IF THEY HAD DISCUSSED MY TARGET ON 1200 MODE C OR NOT, BUT MY DSCNT MAY HAVE SURPRISED THEM. I SHOULD HAVE BROUGHT A COPLT ALONG TO WATCH OR TUNE RADIOS WHILE I CHKED THE ENG AND NAVED ACFT. SHOULD HAVE TUNED RADIOS WHILE IN LEVEL FLT AND THEN STARTED DSCNT. SHOULD HAVE BEEN LOOKING MORE CAREFULLY FOR TFC. HE CAME FROM BELOW L, CLBOUTS COMING TOWARDS YOU ARE SMALL AND NOT MOVING AGAINST THE BACKGND OF CITIES AND FARMS BELOW. SHOULD HAVE INSISTED ON CONTINUING FLT FOLLOWING WITH APCH EVEN THOUGH I WAS CLBING OUT AND LEAVING CLASS C. NEXT TIME I WILL AT LEAST TAKE ALONG AN OBSERVER TO LOOK OUT WHILE I ADJUST AND CHK THINGS. WILL ALSO STAY IN RADAR WITH SOMEONE WHILE THAT CLOSE IN TO A MAJOR ARPT.

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.