INST RATED PVT PLT OF A C172 FAILED TO CANCEL HIS IFR FLT PLAN UPON MAKING A FULL STOP LNDG AT HIS DEST. HE BELIEVED SINCE HE HAD FILED AN IFR RETURN THAT IT WOULD NOT BE REQUIRED TO DO SO.

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I HAD FILED 2 SEPARATE IFR FLT PLANS: BFI TO 75S AND THEN 75S TO BFI. ON MY WAY TO 75S; WHEN ASKED BY WHIDBEY APCH WHAT MY APCH REQUESTS ARE AT 75S; I ASKED FOR THE NDB RWY 10 APCH; FOLLOWING WHICH I INDICATED THAT I WOULD LAND; TAKE OFF; DO SOME MANEUVERS IN THE AREA OVER SOME FARMS; AND THEN HEAD BACK ON THE IFR FLT PLAN BACK TO BFI. I WAS SUBSEQUENTLY CLRED FOR THE APCH. DURING THE SEGMENT OF THE APCH FROM THE IAF TO THE PROC TURN (IF I RECALL CORRECTLY); THE CTLR AGAIN VERIFIED THAT I WANTED TO DO SOME MANEUVERS AFTER EXECUTING THE APCH. AT THAT TIME; I INDICATED THAT I WAS JUST GOING TO LAND; TAKE OFF AGAIN; AND RETURN TO BFI RATHER THAN DOING THE MANEUVERS. THERE WAS A LOT OF TFC ON THIS CLR VMC DAY OVER THE TULIP FARMS; AND I DIDN'T WANT TO HAVE TO WATCH FOR ALL THE TFC WHILE DOING MANEUVERS. THE CTLR CLRED ME TO CHANGE FREQS TO THE 75S CTAF AFTER TELLING ME ABOUT A TWIN CESSNA SAME ALT OPPOSITE DIRECTION. I WAS ALSO CLRED TO EXECUTE THE PUBLISHED MISSED APCH UPON TKOF. AFTER TUNING TO CTAF AND ANNOUNCING THAT I WAS ON THE NDB APCH INBOUND FOR RWY 10; I HEARD THE TWIN CESSNA INDICATE THAT HE WAS GOING TO LAND ON RWY 28. HIS PATTERN ENTRY WAS TOTALLY NONSTANDARD (HE OVERFLEW THE RWY AT CLOSE TO PATTERN ALT; AND THEN TURNED XWIND AND DOWNWIND). I ANNOUNCED THAT I WAS TURNING XWIND BEHIND HIM AND WAS #2 FOR RWY 28. THE WINDS FAVORED RWY 28. DURING THE FINAL APCH AT ABOUT 500 FT; I EXPERIENCED SOME MODERATE TURB. I ASSUMED IT WAS THE WAKE FROM THE TWIN AND KEPT MY SPD UP. AFTER LNDG AND RE-COLLECTING MY WITS; I TAXIED BACK AND DEPARTED AHEAD OF A BONANZA TURNING TO BASE. AT ABOUT 500 FT MSL AFTER DEP; I HEARD MY CALL SIGN AND RECOGNIZED THE VOICE AS THE FEMALE CTLR WHO WAS HANDLING ME DURING THE APCH. I WAS LISTENING TO BOTH APCH AND CTAF AND DIDN'T KNOW WHICH FREQ SHE WAS CALLING ME ON. I SWITCHED TO THE APCH FREQ AND CHKED IN. SHE FIRST ASKED ME IF I WAS EXECUTING THE PUBLISHED MISSED APCH. I INDICATED THAT I WAS DEPARTING RWY 28 AND WAS TURNING L TOWARD THE NDB. SHE THEN ASKED IF I HAD DONE SEVERAL TRIPS IN THE PATTERN; TO WHICH I RESPONDED 'NEGATIVE; I LANDED BEHIND THE TWIN CESSNA; TAXIED BACK AND TOOK OFF AGAIN.' SHE SEEMED FRUSTRATED AND INDICATED THAT SHE HAD KEPT THE AIRSPACE CLOSED TO IFR TFC AND THAT AN IFR FLT PLAN SHOULD BE CLOSED IF A FULL STOP LNDG IS PERFORMED. I DIDN'T RECALL HAVING ASKED FOR A TOUCH-AND-GO; BUT I APOLOGIZED ANYHOW. IT WAS A VMC DAY AND ON THE FINAL APCH SEGMENT I SHOULD HAVE CLOSED THE IFR FLT PLAN. ALTERNATIVELY; THE CTLR COULD HAVE ASKED ME WHETHER I WANT TO CLOSE THE FLT PLAN NOW OR ON THE GND (AS I'D BEEN ASKED ON OTHER FLTS).