AIR TAXI SMT PLT LANDS GEAR UP.

Narrative

I DEPARTED ALLIANCE; NE; FLYING AERO COMMANDER 680. THE WX WAS GOOD AND THE FLT TO NORTH PLATTE; NE; WAS UNEVENTFUL. ABOUT 30 MI DME FROM NORTH PLATTE; I RPTED THE LBF ARPT IN SIGHT AND WAS CLRED BY ZDV FOR A VISUAL APCH TO LBF. I ACKNOWLEDGED THE CLRNC AND BEGAN A GRADUAL DSCNT TO A TFC PATTERN ALT OF 4300 FT. ASOS RPTED THE WX AS CLR BELOW 12000 FT; WINDS 360 DEGS AT 8 KTS. INITIALLY I PLANNED FOR A L DOWNWIND ENTRY FOR RWY 30R BECAUSE I LIKE USING THE LONG RWY WHENEVER POSSIBLE. I RPTED APPROX 15 MI OUT FOR LNDG ON CTAF FREQ 123.0. I LEVELED OFF AT MY TARGET ALT ABOUT 3 MI FROM THE ARPT AND ALLOWED THE ACFT TO SLOW TO ABOUT 120 KTS. AS I APCHED THE ARPT I SAW THAT I WAS SET UP FOR A L BASE ENTRY TO RWY 35. ALTHOUGH RWY 35 IS SHORTER; THE WIND WAS NEARLY DOWN THE MIDDLE; SO I CHANGED MY PLAN AND SET UP FOR RWY 35. I REDUCED PWR; ADDED FLAPS AND RPTED TURNING A 1 MI FINAL FOR RWY 35 ON CTAF. I INTERCEPTED FINAL APCH ON THE VASI GS AND MAINTAINED THE ANGLE AT 100 KTS AND ABOUT 21 INCHES MANIFOLD PRESSURE UNTIL FLARE AND TOUCHDOWN. I WAS NOT AWARE ANYTHING WAS WRONG UNTIL I TOUCHED DOWN ON THE BELLY OF THE ACFT WITH THE GEAR UP. I SKIDDED STRAIGHT AHEAD TO A STOP SLIGHTLY R OF CTRLINE. I SECURED THE ENGS AND SHUT OFF ALL SWITCHES; EXCEPT THE MASTER SWITCH; STROBES; BEACON; AND POS LIGHTS; WHICH I LEFT ON AS I WENT FOR HELP; AND TO NOTIFY COMPANY HEADQUARTERS.