A BEECHCRAFT-60 PILOT PERFORMED AN INTENTIONAL GEAR-UP LANDING AFTER THE RIGHT MAIN LANDING GEAR WOULD NOT EXTEND AFTER NUMEROUS ATTEMPTS.

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ACFT WAS INFLT FOR FIRST TIME FOR 2 NEW ENG BREAK-IN PERIOD OF APPROX 30 MIN FLT. LNDG GEAR SYS MAINT HAD BEEN PERFORMED; SPECIFICALLY FOR GEAR BOX DRIVE FOR EMER EXTENSION. R MAIN GEAR WOULD NOT EXTEND ELECTRICALLY OR MANUALLY (2 ELECTRIC AND 3 MANUAL TRIES WERE CONDUCTED IN ACCORDANCE WITH AFM EMER PROC SECTION). R MAIN GEAR WAS CONFIRMED UP BY VISUAL FROM TWR. DECISION WAS MADE BTWN PLT AND MAINT PERSONNEL TO RAISE ALL GEAR AND CONDUCT GEAR UP LNDG IN ACCORDANCE WITH AFM GEAR UP LNDG EMER PROC SECTION. LANDED GEAR UP ON ASPHALT RWY WITH NO RESULTING SPARKS; FLAME; FIRE; OR INJURIES. ACFT DAMAGE STATUS YET TO BE ASSESSED. QUESTIONED MECH AND VERIFIED GEAR SYS HAD BEEN TESTED REPEATEDLY ON JACKS AFTER GEAR MAINT. POSSIBLE PROB MAY HAVE ARISEN DURING LNDG PHASE OF FLT IN MY DESIRE TO SAVE OR MINIMIZE DAMAGE TO THE NEW ENGS. I ATTEMPTED TO TIME ENG SHUTDOWN OVER RWY TO ALLOW TIME TO STOP ENG/PROPS PRIOR TO TOUCHDOWN. THIS DRAMATICALLY AFFECTED THE FINAL MOMENTS OF AIRSPD CTL AND RATE OF DSCNT; WHICH MAY HAVE RESULTED IN A STALLED CONDITION HAD I NOT BEEN TRAINING NUMEROUS YRS WITH STUDENTS AND BEEN TRAINED TO LOWER THE NOSE FOR SPD. IN RETROSPECT; ONCE THE DECISION HAD BEEN MADE THE ENGS SHOULD NOT HAVE BEEN A CONSIDERATION. ACFT CTL SHOULD HAVE BEEN THE PRIORITY FOR SAFETY OF SOULS ONBOARD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THIS WAS THE FIRST FLIGHT OF THIS ACFT SINCE THE TWO NEW LYCOMING 540 ENGINES WERE INSTALLED. THE ENGINES WERE RUNNING SMOOTHLY DURING THE BREAK-IN PERIOD. HOWEVER; ON APPROACH; HIS RIGHT GEAR WOULD NOT EXTEND. SO A DECISION TO LAND WITH 'INTENTIONAL' GEAR-UP WAS MADE. ACFT WAS LATER PUT UP ON JACKS. GEAR EXTEND/RETRACT OPERATIONAL TESTS WERE PERFORMED AND LANDING GEARS OPERATED WITHOUT FLAW...UNTIL THE 12TH CYCLE OF GEAR SWINGS WHEN THE RIGHT GEAR WOULD NOT COME DOWN. THIS LED TO FURTHER INSPECTION AND OBSERVATION OF A PARTICULAR SPRING APPROX HALF AN INCH LONG INSTALLED WITH THE EXTEND/RETRACT GEAR CABLE. THE BEECHCRAFT MM DIAGRAM SHOWS THE INSTALLATION OF THIS SPRING WHICH PUSHES ON; OR PULLS THE GEAR CABLE; DEPENDING ON THE 'UP' OR 'DOWN' COMMAND FOR THE GEAR. APPARENTLY; THE MM DIAGRAM ONLY SHOWS THE LEFT GEAR SPRING INSTALLATION; NOT THE RIGHT GEAR APPLICATION. THE RIGHT GEAR SPRING WAS INSTALLED SIMILAR TO THE DIAGRAM FOR THE LEFT. IN REALITY; THE RIGHT GEAR SPRING INSTALLATION IS OPPOSITE. REPORTER ALSO STATES THE ACFT WAS FERRIED TO ANOTHER LOCATION FOR FUSELAGE REPAIRS.