NMAC BTWN AN SMT TWIN AND SMA SEL ON FINAL TO PARALLEL RWYS AT A CTLED ARPT.

Narrative

DEPARTED SFO INTL FOR LIVERMORE WHEN RELEASED BY BAY DEP; SQUAWKED 100 ON THE XPONDER. I THEN LISTENED TO THE ATIS WHICH INFORMED ME THAT LIVERMORE WAS USING RWY 25. I IMMEDIATELY SWITCHED TO LIVERMORE TWR AND ADVISED THEM THAT I WAS INBOUND FOR LNDG. THEY ADVISED ME TO LAND AT RWY 25 AND TO ADVISE THEM WHEN I WAS ENTERING THE 45 TO THE DOWNWIND. I WAS EXPERIENCING INTERMITTENT PROBS WITH MY HEADSET; ALTHOUGH THIS PROB DID NOT SHOW UP ON DEP FROM SAN FRANCISCO. I IMMEDIATELY DISCONNECTED THE HEADSET AND SWITCHED ON THE MAIN CABIN SPEAKER. I CALLED ON 3 OR 4 OCCASIONS; ONCE TO ADVISE I WAS ENTERING THE DOWNWIND FROM THE 45 AND 3 OR 4 SEPARATE TIMES TO ADVISE THEM THAT I WAS DOWNWIND (AS I WANTED LNDG INSTRUCTIONS). THE DOWNWIND LEG WAS MADE AT 1500 FT; HOWEVER I EXTENDED IT FURTHER AWAITING RADIO INSTRUCTIONS WHICH WERE NEVER RECEIVED. I DSNDED TO 700 FT ON MY BASE LEG AND PRIOR TO DSNDING; ADVISED THE TWR I WAS TURNING BASE TO FINAL AND THE TWR CLRED ME TO LAND ON RWY 25 R. AT THIS POINT; A CESSNA HIGH WING ACFT FLEW OVER THE TOP OF MY ACFT AT APPROX 70-100 FT. HE WAS NOT VISIBLE UNTIL HE PASSED OVER THE TOP OF ME. I MUST ADMIT THAT I WAS QUITE STARTLED. THE TWR WAS EXTREMELY BUSY AND NEVER ANSWERED ANY OF MY RADIO XMISSIONS AND IT APPEARS THAT THEY DID NOT SEE ME ON THE DOWNWIND. THE OTHER ACFT WAS CLRED APPARENTLY TO MAKE A STRAIGHT IN APCH TO RWY 25L. IT IS MY OPINION THAT IF AN ARPT WAS AS BUSY AT THE TIME AND THE CTLR WAS UNABLE TO RESPOND TO THE ACFT THAT WERE CALLING WHILE THEY WERE IN THE PATTERN; THAT STRAIGHT IN APCHS; UNDER THESE CIRCUMSTANCES; PARTICULARLY ON CONGESTED AIRFIELDS; SHOULD NOT BE ALLOWED. THE PLT OF THE CESSNA 180 WAS APPARENTLY LOOKING DIRECTLY AT ME AS HE WAS COMING INBOUND. THE FEDERAL AVIATION AIRMAN'S INFO MANUAL STATES WITHOUT EQUIVOCATION THAT IT IS PLT'S DUTY TO SEE AND AVOID; IRRESPECTIVE OF RADIO CONTACT; AND IT WAS OBVIOUS THAT THE PLT OF THE CESSNA 180 WAS NEGLIGENT IN THIS MATTER AND HEREBY CONTRIBUTING GREATLY TO THIS INCIDENT.