NMAC BTWN A BEECH 200; AND A MOONEY MO20F; APCHING TO LAND AT AN UNCTLED ARPT. THE KING AIR PLT STATES THAT HE MADE CONTINUOUS TA'S WHEN APCHING; OVERFLYING THE ARPT; AND TURNING FINAL TO LAND. THE MOONEY PLT STATED THAT HE ALSO DID; BUT AFTER DISCUSSION WITH THE OTHER PLT AND HEARING HIS CALLS PRIOR TO DEP; REALIZED THAT HE WAS USING A DIFFERENT NAME FOR THE SAME ARPT; CAUSING THE BEECH PLT TO NOT PAY ATTN TO HIM.

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I TRANSPORTED MY COMPANY'S KING AIR 200 AND 6 PAX TO SSI ON JUL/XX/98. I HAD A DAY PLT IN R SEAT. THE FLT WAS VMC UNDER AN IFR FLT PLAN. UPON GAINING A VISUAL ON SSI; WE CANCELED IFR AND WENT IN UNDER VFR. WE WERE APPROX 10 MI NW. WE CALLED LCL ADVISORY FREQ AND ADVISED TFC OF OUR INTENTIONS TO LAND AT SSI. THERE WAS ANOTHER C172/182 4-6 MI NE INBOUND FOR STRAIGHT IN RWY 22. HE CALLED US AND SAID HE WOULD DROP IN BEHIND US. I ELECTED NOT TO; AND HAD THE COPLT ADVISE THE CESSNA TO CONTINUE AND WE WOULD OVERFLY THE FIELD AND ENTER L DOWNWIND FOR RWY 22. WE GOT A VISUAL ON THE CESSNA ON FINAL AND CONTINUED TO THE FIELD MAKING RADIO CALLS AT EACH POS: 5 MI OUT; OVER FIELD FOR L HAND DOWNWIND RWY 22; ENTERING DOWNWIND; TURNING BASE. AS WE CROSSED THE FIELD; I INSTRUCTED THE COPLT TO LOOK DOWN THE BEACH FOR TFC AND I WOULD LOOK UP THE BEACH FOR TFC; NEITHER OF US SAW ANY TFC. AS I STATED; WE CALLED ENTERING DOWNWIND. AS WE CALLED TURNING L BASE FOR RWY 22; AND AS I STARTED TO TURN BASE; I SAW A MOONEY PASS JUST UNDER THE NOSE OF MY ACFT HEADING NW; (FROM R TO L). HE WAS ONLY 200 FT AT MOST BELOW US. HE PROCEEDED ON A 'MODIFIED BASE' TO RWY 22 THEN TURNED FINAL AND LANDED ON RWY 22 AT SSI. NO RADIO CALLS OR ANYTHING. THE OTHER CESSNA SAW HIM ON FINAL AND CALLED US TO MAKE SURE WE HAD SEEN HIM; AND WE HAD. HE TOOK HIS TIME CLRING THE RWY SO I FEEL HE NEVER SAW US. UPON ARR ON THE RAMP I CONFRONTED THE PLT OF THE MOONEY ABOUT HIS ACTIONS AND WHY HE WAS NOT USING HIS RADIO. HE SAID HE ENTERED THE PATTERN ON THE DOWNWIND AND WAS USING THE RADIO. HE ORIGINALLY STATED HE DID NOT SEE US THEN SAID HE DID. I DO NOT BELIEVE HE EVER SAW US. RADAR AND A TWR AT SSI IS THE ONLY WAY THIS COULD HAVE BEEN AVOIDED; UNLESS THE PLT OF THE MOONEY HAD USED PROPER UNCTLED PATTERN/APCH TECHNIQUES AND HIS RADIO. I HAVE SUBMITTED A COMPLAINT TO THE FAA REGARDING THIS INCIDENT. SUPPLEMENTAL INFO FROM ACN 407550: WE ARGUED ABOUT RADIO CALLS; HE INSISTED HE MADE HIS APCHING SSI FROM THE NW. I DIDN'T HEAR HIS DOWNWIND CALL. ON LATER ANALYSIS I REALIZED WHY. HE WAS CALLING MALCOLM-MCKINNON TFC; WHILE I CALLED SAINT SIMON'S TFC. I ASSUMED I WAS HEARING OTHER ARPT TFC AND ONLY PAID ATTN TO/AND LISTENED FOR THE WORDS SAINT SIMON. I DISCOVERED THIS WHEN WE WERE BOTH PREPARING OUR DEP TAXIS. BOTH NAMES ARE USED -- IT'S MALCOLM MCKINNON ARPT WITH IDENTIFIER SSI. IN RETROSPECT; I SHOULD HAVE REGISTERED THE CALLS HE MADE AND SEQUENCED ACCORDINGLY.