C170 INSTRUCTOR PLT TAKES EVASIVE ACTION WHEN TURNING BASE TO FINAL RWY 29 SJC WHEN HE OBSERVES A C172 BELOW AND TO HIS L ON A STRAIGHT-IN FOR RWY 29. APPARENTLY; ONE LCL CTLR FAILED TO COORD OTHER TFC LNDG RWY 29 IN THE OTHER LCL CTLR DELEGATED AIRSPACE.

Narrative

PVT PLT WAS FLYING. WE (ACFT X) WERE INBOUND FROM RIO VISTA TO SJC. OVER SUNOL; BAY TOLD US TO 'CROSS THE SUITES' AT 2500 FT.' HE THEN TOLD US TO CONTACT SJC TWR. SJC LCL CTLR TOLD US TO FLY OVER THE FIELD AT 2000 FT AND ENTER A L DOWNWIND FOR RWY 29. HE CAME BACK SHORTLY AND SAID; 'THERE'S NOT ANOTHER ACFT FOR 50 MI; MAKE A R DOWNWIND FOR RWY 29; CLRED TO LAND.' THE PVT PLT MADE A DOWNWIND ENTRY; TURNED ONTO BASE; AND THEN BEGAN A R TURN ONTO FINAL. WE HAD DSNDED TO 400 FT OR 500 FT BY THIS TIME. AS WE WERE TURNING; I SAW A STROBE LIGHT COME OUT FROM UNDER OUR NOSE. IT WAS ATTACHED TO A NEW WHITE CESSNA 172 (ACFT Y) THAT WAS ON FINAL FOR RWY 29. THE CESSNA (ACFT Y) WAS APPARENTLY ON THE OTHER LCL FREQ; BECAUSE WE HEARD NO XMISSIONS TO OR FROM THE ACFT. I IMMEDIATELY TOOK THE CTLS; ADDED PWR; AND MADE A L CLBING TURN TO AVOID A COLLISION. THE TWR CTLR SAID; 'SORRY ABOUT THAT; MAKE A L 270 DEG TURN AND RE-ENTER ON FINAL.' WE LANDED WITHOUT FURTHER INCIDENT AND OBSERVED THE OTHER ACFT TAXIING BACK FOR TKOF.