Narrative:

Being vectored for ILS by approach control about 15 clear of clouds. Approach control called traffic 12 O'clock +/- 3 mi. We were in clouds and called traffic did not appear on the TCAS, I requested turn around traffic that approach control confirmed as primary target. The first officer, a former fgt pilot complied with a 'tight' right turn toward the final approach fix. Approach control said the other traffic would pass about 1/4 mi behind us. As we rolled out of turn, we flew out of clouds and saw other plane. I think it was an small aircraft pass above (about 200 ft) and about 1/4 mi behind. Approach control said he got two replies from the other aircraft's transponder. Our TCAS showed none. A week earlier, being vectored to same runway, same flight, our TCAS commanded a 'climb, climb!' when we were again in the clouds at 6000 ft. A light plane had been climbing to VFR on top at 5500 ft (tops of broken clouds we reported as 7000 ft). The first TCAS RA was at 3 O'clock, 600 ft below, followed by a second at 12 O'clock, 600 ft below. The RA continued to instruct a 2500 FPM climb. As we flew out of cumulus, the 12 O'clock traffic disappeared. The TCAS report that I submitted indicated that I thought the 12 O'clock traffic was a ghost because it was only in view for a few seconds and not seen by approach control. Then I began to think what would happen if a pilot were to shut off his/her transponder to avoid being 'caught'....not as far fetched as it might seem. Stupid, yes. By phone, approach control said that they catch quite a few that get a talking to by GADO... I sure hope it does not become a norm to shut off the transponder when you think you have just screwed up. Anybody can get lost momentarily. Most of us have been once or twice. Not many survive midairs.

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Original NASA ASRS Text

Title: TA GIVEN WHILE ACFT DSNDING THROUGH CLOUDS.

Narrative: BEING VECTORED FOR ILS BY APCH CTL ABOUT 15 CLR OF CLOUDS. APCH CTL CALLED TFC 12 O'CLOCK +/- 3 MI. WE WERE IN CLOUDS AND CALLED TFC DID NOT APPEAR ON THE TCAS, I REQUESTED TURN AROUND TFC THAT APCH CTL CONFIRMED AS PRIMARY TARGET. THE FO, A FORMER FGT PLT COMPLIED WITH A 'TIGHT' R TURN TOWARD THE FINAL APCH FIX. APCH CTL SAID THE OTHER TFC WOULD PASS ABOUT 1/4 MI BEHIND US. AS WE ROLLED OUT OF TURN, WE FLEW OUT OF CLOUDS AND SAW OTHER PLANE. I THINK IT WAS AN SMA PASS ABOVE (ABOUT 200 FT) AND ABOUT 1/4 MI BEHIND. APCH CTL SAID HE GOT TWO REPLIES FROM THE OTHER ACFT'S XPONDER. OUR TCAS SHOWED NONE. A WK EARLIER, BEING VECTORED TO SAME RWY, SAME FLT, OUR TCAS COMMANDED A 'CLB, CLB!' WHEN WE WERE AGAIN IN THE CLOUDS AT 6000 FT. A LIGHT PLANE HAD BEEN CLBING TO VFR ON TOP AT 5500 FT (TOPS OF BROKEN CLOUDS WE RPTED AS 7000 FT). THE FIRST TCAS RA WAS AT 3 O'CLOCK, 600 FT BELOW, FOLLOWED BY A SECOND AT 12 O'CLOCK, 600 FT BELOW. THE RA CONTINUED TO INSTRUCT A 2500 FPM CLB. AS WE FLEW OUT OF CUMULUS, THE 12 O'CLOCK TFC DISAPPEARED. THE TCAS RPT THAT I SUBMITTED INDICATED THAT I THOUGHT THE 12 O'CLOCK TFC WAS A GHOST BECAUSE IT WAS ONLY IN VIEW FOR A FEW SECONDS AND NOT SEEN BY APCH CTL. THEN I BEGAN TO THINK WHAT WOULD HAPPEN IF A PLT WERE TO SHUT OFF HIS/HER XPONDER TO AVOID BEING 'CAUGHT'....NOT AS FAR FETCHED AS IT MIGHT SEEM. STUPID, YES. BY PHONE, APCH CTL SAID THAT THEY CATCH QUITE A FEW THAT GET A TALKING TO BY GADO... I SURE HOPE IT DOES NOT BECOME A NORM TO SHUT OFF THE XPONDER WHEN YOU THINK YOU HAVE JUST SCREWED UP. ANYBODY CAN GET LOST MOMENTARILY. MOST OF US HAVE BEEN ONCE OR TWICE. NOT MANY SURVIVE MIDAIRS.

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.