A PIPER ARROW IN CRUISE AT 4500 FT ADVISED ATC OF LOSS OF ELECTRICAL PWR. WITH ATC ASSISTANCE LANDED AT CPR. GEAR UP LNDG INCURRING DAMAGE.

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FLYING VFR AT 4500 FT FROM POST ISABEL; TX ARPT TO CORPUS CHRISTI ARPT; THE ACFT EXHIBITED PARTIAL ELECTRICAL PWR FAILURE. THIS DETERMINATION WAS MADE AFTER AN INFLT CRUISE CHKLIST REVEALED THAT THE AMMETER INDICATOR NEEDLE WAS READING LOW. FURTHER INFLT XCHKS AND XREFS WERE DONE TO CHK THE STATUS OF THE AMMETER. THIS COLLABORATED A POSSIBLE MALFUNCTION OF THE ALTERNATOR; OR ELECTRICAL SYS. THE AMMETER DID NOT EXHIBIT THIS READING DURING PREFLT CHKS AND 'RUN-UPS' CHKS. THE DISPLAY WAS A NORMAL READING. AT THIS POINT IN THE FLT; ATC WAS NOTIFIED. THE CTLR ACKNOWLEDGED AND CONSIDERATION WAS DISCUSSED AS TO THE POSSIBILITY OF A TOTAL ELECTRICAL PWR FAILURE OF THE ACFT'S ELECTRICAL SYS. THE CTLR ADVISED THAT HE WOULD COORDINATE WITH CORPUS CHRISTI TWR FOR APCH AND LNDG WITHOUT THE NEED FOR ANY FURTHER 2-WAY RADIO COMS. ATC ADVISED OF THE CLRED PROCS DIRECT AND CLRED TO LAND ON RWY 35. THEN FINALLY; THE AIR TFC CTLR PROVIDED THE DISTANCE AND THE LOCATION OF THE ARPT (AT 12 O'CLOCK POS; AND 20 NM). AT THIS TIME; ALL FURTHER RADIO COMS WITH ATC WERE DISCONTINUED; AND ALL UNNECESSARY ELECTRICAL COMPONENTS WERE TURNED OFF; EXCEPT FOR THE XPONDER AND NAV LIGHTS; BOTH OF WHICH WERE VISUALLY FUNCTIONAL. THE XPONDER WAS LEFT ON THE ORIGINAL SQUAWK CODE FOR TRACKING PURPOSES; AS INSTRUCTED BY ATC. THE NAV LIGHTS WERE LEFT ON FOR SAFETY REASONS AND SPOTTING OF THE ACFT BY TWR PERSONNEL. UPON FINAL APCH AT APPROX 6 MI S OF THE ARPT; IN PREPARATION FOR LNDG; EXECUTION OF CHKLISTS FOR NORMAL LNDG WERE INSTITUTED. WITH THE XPONDER STILL INDICATING A SIGNAL; AND NAV LIGHT STILL VISUALLY FUNCTIONAL; THE LNDG GEAR LEVER WAS ACTIVATED AND THE LNDG GEAR EXTENSION SOUND AND RESPONSE WAS HEARD AND FELT. THIS PROVIDED AN INDICATION THAT THE LNDG HAD EXTENDED. THE 3 GREEN INDICATOR LIGHTS FOR THE LNDG GEAR DID NOT ILLUMINATE; BUT DUE TO THE FEEL AND SOUND CREATED BY THE ACFT'S LNDG GEAR; AND THE FACT THE ELECTRICAL PWR OUTPUT WAS LOW; THE PLT CONCLUDED THAT THE GEAR HAD SUCCESSFULLY EXTENDED AND THE 3-GREEN DID NOT ILLUMINATE DUE TO LOW PWR OUTPUT; THEREFORE NO FURTHER ACTIONS WERE NECESSARY FOR A NORMAL AND SAFE LNDG. THE APCH TO LNDG WAS NORMAL; OTHER THAN EXECUTED IN TOTAL COCKPIT DARKNESS; BECAUSE THE PLT HAD TURNED OFF ALL UNNECESSARY EQUIP. UPON FARING A SCREECHING SOUND EMITTED FROM THE LNDG GEAR DRAGGING ON THE RWY'S SURFACE; FOLLOWED BY THE SOUND OF THE PROP STRIKING THE RWY; THEN FINALLY THE BELLY OF THE ACFT SMOOTHLY SKIDDING ON THE RWY FOR APPROX 100 FT. THE IMPACT OF THE ACFT LNDG WITHOUT THE FULLY EXTENDED LNDG GEAR; THOUGH NOT CONSIDERED A PLUS; FELT RELATIVELY MILD AND COMPATIBLE TO A VERY MINOR VEHICULAR FENDER BENDER ACCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE LOSS OF ELECTRICAL PWR WAS THE ALTERNATOR. THE RPTR SAID NO EMER WAS DECLARED AS AFTER ADVISING ATC OF THE ELECTRICAL PROB; ATC COORDINATED THE CLRNC INTO CPR. THE RPTR STATED WHEN THE GEAR HANDLE WAS LOWERED; IT SOUNDED AND FELT LIKE THE GEAR WAS FULLY EXTENDED. THE RPTR SAID THE LNDG WAS SMOOTH BUT INCURRED MINOR DAMAGE TO THE LOWER BELLY SKIN.