Narrative:

On descent into tpa we were cleared to 5000' on a heading of about 120 degrees for vectors for a visual approach to runway 18L. There was a small thunderstorm in front of us and we were in and out of clouds. We asked for a deviation to the left (north) and requested a lower altitude to get below the clouds. Tpa approach gave us our requested deviation and cleared us to 2000'. We got around the storm and continued our descent to 2000'. We advised approach control that we could turn to any heading that he wanted as we were around the WX. Approach said to maintain our present heading, about 110 degrees. On that heading we broke out of the clouds about 3500'. The controller asked if we had the airport in sight and we said yes. He cleared us for a visual approach to runway 18L. The first officer was flying the aircraft. About an altitude of +/-2500' at 12:30-1 O'clock position at 1/4 mi, I saw an small aircraft on an apparent collision course with us. I took control of the aircraft and made an immediate left climbing turn. The aircraft passed about 200-300' underneath us and about 1000' behind us. On our pull up a F/a was knocked to the floor. Many passenger saw the other aircraft. There were no injuries to passenger or crew except the F/a received a rug burn on her knee. I spoke with the supervisor at tpa approach control and he said the small aircraft never showed up on radar. I think in this situation that there was no one at fault, but there still could have been a midair. The system someday may require all small aircraft operating VFR to have a transponder automatically turned on by a switch in the landing gear.

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Original NASA ASRS Text

Title: CLOSE PROX ACR-LGT GA-SMA NEAR TPA ARSA.

Narrative: ON DSCNT INTO TPA WE WERE CLRED TO 5000' ON A HDG OF ABOUT 120 DEGS FOR VECTORS FOR A VISUAL APCH TO RWY 18L. THERE WAS A SMALL TSTM IN FRONT OF US AND WE WERE IN AND OUT OF CLOUDS. WE ASKED FOR A DEVIATION TO THE LEFT (N) AND REQUESTED A LOWER ALT TO GET BELOW THE CLOUDS. TPA APCH GAVE US OUR REQUESTED DEVIATION AND CLRED US TO 2000'. WE GOT AROUND THE STORM AND CONTINUED OUR DSCNT TO 2000'. WE ADVISED APCH CTL THAT WE COULD TURN TO ANY HDG THAT HE WANTED AS WE WERE AROUND THE WX. APCH SAID TO MAINTAIN OUR PRESENT HDG, ABOUT 110 DEGS. ON THAT HDG WE BROKE OUT OF THE CLOUDS ABOUT 3500'. THE CTLR ASKED IF WE HAD THE ARPT IN SIGHT AND WE SAID YES. HE CLRED US FOR A VISUAL APCH TO RWY 18L. THE F/O WAS FLYING THE ACFT. ABOUT AN ALT OF +/-2500' AT 12:30-1 O'CLOCK POS AT 1/4 MI, I SAW AN SMA ON AN APPARENT COLLISION COURSE WITH US. I TOOK CTL OF THE ACFT AND MADE AN IMMEDIATE LEFT CLBING TURN. THE ACFT PASSED ABOUT 200-300' UNDERNEATH US AND ABOUT 1000' BEHIND US. ON OUR PULL UP A F/A WAS KNOCKED TO THE FLOOR. MANY PAX SAW THE OTHER ACFT. THERE WERE NO INJURIES TO PAX OR CREW EXCEPT THE F/A RECEIVED A RUG BURN ON HER KNEE. I SPOKE WITH THE SUPVR AT TPA APCH CTL AND HE SAID THE SMA NEVER SHOWED UP ON RADAR. I THINK IN THIS SITUATION THAT THERE WAS NO ONE AT FAULT, BUT THERE STILL COULD HAVE BEEN A MIDAIR. THE SYS SOMEDAY MAY REQUIRE ALL SMA OPERATING VFR TO HAVE A TRANSPONDER AUTOMATICALLY TURNED ON BY A SWITCH IN THE LNDG GEAR.

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.