Narrative:

Air carrier X cleared for the ILS to runway 30L at sjc. WX was 2000 ft broken and 7 NM visibility. As I made the 500 ft call to the captain, who was flying, I saw a cessna just ahead of us and slightly above us to the left, apparently lined up to do a touch and go to runway 29, the general aviation runway. Passing about 300 ft, he suddenly started swerving toward us. The tower immediately told him to go around to the left. At about 200 ft, his closest point of approach to us (about 300 ft), the cessna executed a hard left climbing turn. I believe this situation is caused by 2 factors: first, the 2 runways appear to be less than 1000 ft apart. Second, the cessna was cleared to land provided he kept us in sight visually, which he obviously did not. Tower should not let runway 29 traffic turn base unless clear of runway 30L traffic. Supplemental information from acn 307631. Air carrier X on final approach on runway 30L at sjc below 200 ft. Suddenly I noticed a C172 in a hard left turn at about 45 degrees of bank at my altitude very close within 300 ft. There is no way he could have seen us but the tower said that the cessna had us in sight. This is a very dangerous situation.

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Original NASA ASRS Text

Title: MULTIPLE RWY OP PARALLEL RWYS ACR X HAD NMAC WITH C172 ON APCH TO PARALLEL RWY. SEE AND AVOID CONCEPT.

Narrative: ACR X CLRED FOR THE ILS TO RWY 30L AT SJC. WX WAS 2000 FT BROKEN AND 7 NM VISIBILITY. AS I MADE THE 500 FT CALL TO THE CAPT, WHO WAS FLYING, I SAW A CESSNA JUST AHEAD OF US AND SLIGHTLY ABOVE US TO THE L, APPARENTLY LINED UP TO DO A TOUCH AND GO TO RWY 29, THE GENERAL AVIATION RWY. PASSING ABOUT 300 FT, HE SUDDENLY STARTED SWERVING TOWARD US. THE TWR IMMEDIATELY TOLD HIM TO GAR TO THE L. AT ABOUT 200 FT, HIS CLOSEST POINT OF APCH TO US (ABOUT 300 FT), THE CESSNA EXECUTED A HARD L CLBING TURN. I BELIEVE THIS SIT IS CAUSED BY 2 FACTORS: FIRST, THE 2 RWYS APPEAR TO BE LESS THAN 1000 FT APART. SECOND, THE CESSNA WAS CLRED TO LAND PROVIDED HE KEPT US IN SIGHT VISUALLY, WHICH HE OBVIOUSLY DID NOT. TWR SHOULD NOT LET RWY 29 TFC TURN BASE UNLESS CLR OF RWY 30L TFC. SUPPLEMENTAL INFO FROM ACN 307631. ACR X ON FINAL APCH ON RWY 30L AT SJC BELOW 200 FT. SUDDENLY I NOTICED A C172 IN A HARD L TURN AT ABOUT 45 DEGS OF BANK AT MY ALT VERY CLOSE WITHIN 300 FT. THERE IS NO WAY HE COULD HAVE SEEN US BUT THE TWR SAID THAT THE CESSNA HAD US IN SIGHT. THIS IS A VERY DANGEROUS SIT.

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.