What was found
UPON APPROACH INTO LANAI (APX 2035 HST) DURING A PATIENT PICKUP LEG,THE RIGHT MAIN LANDING GEAR (RMLG) INDICATOR LIGHT EXTINGUISHED AFTER INITIALL SHOWING 'GREEN'. LANDING GEAR HAD BEEN DOWN/LOCKED FOR NEARLY A MINUTE, AND THE RMLG FADED/FLICKERED ONCE, THEN WENT OUT. DISCONTINUED APPROACH AT LANAI, DECLARED EMERGENCY, AND RETURNED HONOLULU. LOWERING GEAR AT HNL, ALL THREE LG INDICATOR LIGHTS REMAINED 'GREEN' FOR THE DURATION OF FLIGHT/LANDING/TAXI/SHUT-DOWN. (DOWNSIDE HYDRAULIC PRESSURE ALSO ADDED VIA HAND-CRANK.) REPLACED RH MLG DOWNLOCK SWITCH. GROUND OPERATIONAL CHECK SATISFACTORY