BE55 PLT INADVERTENTLY RAISES THE LNDG GEAR AFTER CLRING THE RWY AT ZZZ.

Narrative

I PLANNED TO FLY A SOMEWHAT WIDER THAN NORMAL PATTERN IN ORDER TO HAVE SUFFICIENT TIME TO DOUBLE-CHK EVERYTHING AND TO SET UP ACCURATE APCH SPDS; BUT MADE THE PATTERN TIGHTER WHEN I HEARD THE TWR TELL ANOTHER PLANE RPTING ON THE ILS TO RWY 3 THAT THEY WERE SECOND TO MY BARON IN THE PATTERN. I JUDGED I WAS SOMEWHAT HIGH; AND SO I DECREASED MANIFOLD PRESSURE TO 12 INCHES AND PITCHED UP SO THAT I WOULD BE AT 100 KTS ON SHORT FINAL. THE LNDG WAS A 'SQUEAKER' AND WAS RIGHT ON THE ILS LNDG BARS. I HAD CHKED THE GEAR PANEL LIGHT AND ALSO MECHANICAL INDICATOR LOCATED ON THE FLOOR AS I LOWERED THE LNDG GEAR WHEN PARALLEL TO THE NUMBERS ON DOWNWIND; AND AGAIN WHEN REPEATING THE 'GUMPS CHK' TURNING BASE AND FINAL. I DID A FINAL CHK OF THE GEAR PANEL LIGHT AT 200 FT AGL; AT THE SAME TIME I WENT TO FULL PROP AND MIXTURE. PROUD OF 'RESCUING' THE LESS-THAN-IDEAL APCH; I NOTED ON THE ROLLOUT THAT THE OVERHAULED FUEL INJECTION SYS NOW IDLED BOTH ENGS AT 625 RPM AND THAT THE R WHEEL BRAKE FUNCTIONED PROPERLY. (PRIOR TO OVERHAUL; THE L ENG HAD TO STAY AT 1000 RPM TO AVOID STOPPING; AND THE R TOE BRAKE NEEDED TO BE PUMPED TO PREVENT IT FROM GOING TO THE FLOOR.) I WAS COMING UP ON TXWY D; WHICH IS HALFWAY DOWN THE 6000 FT RWY AND WOULD LEAD ME QUICKLY BACK TO OUR HANGAR. IN A MENTAL LAPSE THAT IS STILL ASTOUNDING TO ME AFTER 5 DAYS OF ALMOST CONSTANT REFLECTION; I REACHED DOWN TO RETRACT THE FLAPS; AS I HAD FOUND TO BE EFFECTIVE IN SHORT FIELD LNDG PRACTICE IN A C172. I FELT THE PLANE JUMP SLIGHTLY; WHICH I THINK MAY HAVE UNLOADED THE SQUAT SWITCH; AND THEN FIRST THE NOSE AND THEN THE L WING DROPPED. THE SPD HAD ALREADY DROPPED TO ABOUT 20 KTS; AND THE RESULTING SLIDE WAS SHORT. I CUT THE MAGNETOS AND MASTER AND TURNED BOTH FUEL HANDLES TO OFF AND EXITED THE PLANE. AFTER SMELLING NO SPILT FUEL; I WENT BACK INTO THE COCKPIT TO CHK THE SWITCHES. I TURNED ON THE MASTER TO SEE IF I COULD CALL THE TWR. THE XMITTER DID NOT WORK; BUT I COULD SEE THAT CRASH TRUCK ALREADY COMING. I HAD BEEN SO CONCERNED ABOUT WHAT I HAD READ ABOUT INADVERTENT GEAR RETRACTION IN A BARON AND BONANZA; THAT I HAD OBTAINED (BUT UNFORTUNATELY NOT YET INSTALLED) A PLASTIC DEVICE THAT BLOCKS MOVING THE GEAR LEVER UPWARDS UNTIL IT IS PUSHED ASIDE. I THINK THE 3-MONTH LAPSE AND MY CONCENTRATING ON NOT MISSING ANY CHKLIST ITEM LED ME TO FORGET MY HABIT OF KEEPING MY L-HAND ON THE CTL HORN AND THE R-HAND LOCKED ON THE THROTTLE UNTIL OFF THE RWY. IN RETROSPECT; I FEEL THE ACCIDENT WAS PERHAPS THE RESULT OF MY CONCENTRATING ON THE CHKLIST DETAILS WHEN FLYING A MORE COMPLEX ACFT; AND ALSO ON HOW THE PLANE WAS FUNCTIONING AFTER THE OVERHAUL. I FEEL I SHOULD HAVE BEEN FOCUSING MORE ON SOME OF THE ESSENTIALS OF FLYING A RETRACTABLE TWIN -- LIKE KEEPING THE R-HAND ON THE THROTTLES UNTIL OFF THE RWY AND FULLY STOPPED. FINALLY; I THINK THAT BEING SOMEWHAT RUSHED ALSO CONTRIBUTED TO THE MENTAL LAPSE. I HAVE NOTED THAT ERRORS AND OMISSIONS TEND TO OCCUR WHEN I AM RUSHING; BUT IN THE PAST THEY WERE ALL MINOR; NOT THIS EMBARRASSING AND EXPENSIVE.