GEAR UP LNDG BY PLT IN SMA.

Narrative

ACFT; A SINGLE ENG; SIGHTSEEING FLT WITH 4 PAX. APPROX 1/2 WAY THROUGH THE FLT I NOTICED THE AMMETER SHOWING A LOW CHARGE. THE ALTERNATOR LIGHT WAS NOT ILLUMINATED. I CHKED THE LIGHT AND FOUND IT TO BE IN WORKING CONDITION. AT THIS POINT I DECIDED TO REDUCE THE ELECTRICAL LOAD. EVERYTHING WAS TURNED OFF EXCEPT #1 AND #2 COM RADIOS; TRANSPONDER; AND ANTI-COLLISION LIGHTS. THE AMMETER SHOWED A SLIGHT INCREASE; SO THE AIR CONDITIONER WAS TURNED BACK ON; AND THE AMMETER STAYED RELATIVELY THE SAME. NOTE: THE ALTERNATOR SWITCH WAS RECYCLED BEFORE AND AFTER THE LOAD HAD BEEN REDUCED. THE TWR WAS CONTACTED ONCE THE FLT WAS NEARING 10 MI E OF THE ARPT. THE TWR GAVE INSTRUCTIONS TO ENTER 'R TFC FOR RWY 8R.' WHEN THE ACFT WAS NEARING R BASE I REALIZED A R 360 DEG TURN WAS NECESSARY AND WAS REQUESTED. TFC WAS RPTED BY THE TWR TO BE ON FINAL FOR 8R. I RPTED THE TFC IN SIGHT AND MY R 360 DEG TURN WAS APPROVED. IT WAS AT THIS POINT THAT I PLACED THE GEAR SELECTOR IN THE DOWN POS. I COULD HEAR THE GEAR MOTOR RUNNING. THE FIRST POS OF FLAPS WAS ADDED (10 DEGS). I BEGAN THE R 360 DEG TURN AND CHKED FOR 3 GREEN GEAR LIGHTS. THE LIGHTS APPEARED TO BE ON AND EVERYTHING WAS NORMAL. ONCE I JOINED FINAL APCH FOR THE RWY I COMPLETED MY FINAL PRE-LNDG CHK. THE APCH WAS NORMAL AND EVERYTHING WAS IN ORDER. PWR WAS CARRIED TO THE THRESHOLD. UPON REACHING THE THRESHOLD THE PWR WAS REDUCED TO IDLE. NO GEAR OR STALL WARNING WAS HEARD. THE ACFT SLID ON ITS BELLY WITH THE PROP STRIKING THE RWY. IT HAD SLID ABOUT 250 YARDS BEFORE COMING TO REST. ONCE AT REST I IMMEDIATELY SHUT OFF THE MASTER; FUEL PUMP; AND ANTI-COLLISION LIGHTS. I GOT OUT OF THE ACFT AND ASSISTED THE PAX IN EXITING THE ACFT. ALL OF THE PAX WERE FINE. I ASKED THEM TO STAND OFF TO THE SIDE OF THE RWY. I WENT BACK TO THE ACFT AT THIS TIME AND RAISED THE FLAPS AND SHUT OFF THE FUEL. THE RADIOS WERE ALSO TURNED OFF ALONG WITH THE MAGNETOS. THE ACFT SHOWED NO SIGNS OF FUEL LEAKS OR OIL LEAKS; AND THERE WAS NO SIGN OF SMOKE. I AM NOT SURE WHAT CAUSED THE PROBLEM. THE ONLY DEDUCTION I CAN THINK OF IS THAT THE SUN WAS SHINING ON THE INST PANEL BOTH TIMES I CHKED THE GEAR. THE LIGHTS WOULD NOT HAVE COME ON WITHOUT THE GEAR BEING DOWN AND LOCKED. WHEN THE ACFT WAS HOISTED OFF ITS BELLY THE MASTER SWITCH WAS TURNED ON AND THE GEAR CAME DOWN. THE ONLY SOLUTION WOULD HAVE BEEN TO TAKE MY HANDS OFF THE WHEEL DURING A CRITICAL PHASE OF FLT IN ORDER TO MAKE SURE THE SUN WAS NOT ILLUMINATING THE GEAR LIGHTS.