A PA-28 EXPERIENCED A NEAR MISS WITH A PA-31 ON FINAL APPROACH AT PAO.

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ACFT #1; PLTED BY ME; HAD DEPARTED PALO ALTO; AND ITS PURPOSE WAS AN INST PROFICIENCY CHK. I WAS IN THE L SEAT; AND INSTRUCTOR WAS IN THE R SEAT. AFTER COMPLETING THE CHK; WE WERE RETURNING TO PALO ALTO VFR. THE TWR WAS OPERATING. WE CONTACTED THE TWR OUTSIDE CLASS D; AND WERE INSTRUCTED TO MAKE R TFC FOR RWY 31. AS WE APCHED THE ARPT ON A 45 DEG ENTRY; WE WERE SEQUENCED BEHIND A CESSNA SINGLE ALREADY IN THE R DOWNWIND. AFTER WE HAD PASSED ABEAM THE APCH END OF RWY 31; WE WERE CLRED TO LAND; #3 BEHIND 2 CESSNA SINGLES. ONE OF THESE SINGLES WAS ON R BASE; THE OTHER WAS THE TFC WE WERE FOLLOWING ON DOWNWIND. WE ACKNOWLEDGED THE CLRNC; AND RPTED BOTH CESSNAS IN SIGHT. WHEN WE TURNED R BASE; #1 CESSNA WAS ON FINAL -- ABOUT 1 MI -- AND #2 CESSNA WAS ON A LONG FINAL; OVER THE SHORELINE AMPHITHEATER. DURING OUR TURN TO BASE; WE HEARD THE TWR INSTRUCTING ANOTHER ACFT TO CLB TO 1500 FT AND MAKE A TURN. WE DID NOT HAVE THIS ACFT IN SIGHT; NOR DID WE KNOW ITS PRECISE LOCATION. WE SUBSEQUENTLY TURNED FINAL; WITH BOTH CESSNAS IN SIGHT AHEAD OF US. CESSNA #1 LANDED ON RWY 31; USING THE FULL LENGTH OF THE RWY. IT WAS APPARENT THAT CESSNA #2 WOULD BE UNABLE TO LAND BEFORE CESSNA #1 CLRED THE RWY. THE TWR INSTRUCTED CESSNA #2 TO GO AROUND. WE THUS BECAME #1 TO LAND; AND IT WAS CLR THAT THE FIRST CESSNA WOULD EXIT THE RWY IN TIME TO PERMIT US TO LAND SAFELY. THE TWR THEN CALLED US; AND INSTRUCTED US TO GO AROUND. AT THAT POINT; WE WERE AT 400 FT AND INDICATING 60 KTS. I ACKNOWLEDGED THE INSTRUCTION; AND APPLIED PWR AND BACK PRESSURE. JUST AS OUR ACFT HAD LEVELED OFF; BUT BEFORE WE HAD STARTED TO CLB; A PIPER CHEYENNE FLEW ABOVE US. HE WAS MOVING AT LEAST 30 KTS FASTER THAN US. HIS L ENG WAS ABOVE OUR COCKPIT. I ESTIMATE THE VERT CLRNC BTWN THE 2 ACFT AT 25 FT. AFTER HE PASSED US; WE EXPERIENCED A SIGNIFICANT ROLL IMPULSE DUE TO THE CHEYENNE'S WAKE; BUT WERE ABLE TO REGAIN CTL. I BELIEVE THAT IF I HAD IMMEDIATELY COMPLIED WITH THE GAR INSTRUCTION; BEFORE ACKNOWLEDGING IT; I WOULD HAVE COLLIDED WITH THE CHEYENNE. IT SEEMS TO ME THAT THE OVERTAKING ACFT; THE CHEYENNE; SHOULD HAVE BEEN INSTRUCTED TO GO AROUND. THEY WERE THE OVERTAKING ACFT. WE RPTED THE NEAR MISS TO THE TWR. WE COMPLETED THE GAR AND A CIRCUIT OF THE PATTERN; AND LANDED UNEVENTFULLY.