What was found
DURING DESCENT TRIED TO START THE APU. GOT THE "APU FAIL" LIGHT AFTER HITTING THE START SWITCH. VISUAL INSP SHOWS SIGN OF A FIRE NEAR THE INTAKE OF THE APU. GAINED ACCESS TO APU EXTERIOR AND ACCOMPLISHED VISUAL INSP OF EXTERIOR COMPONENTS AND ACCESSORIES IAW MM 49-00-00 AND BOROSCOPED INLET IAW 49-20-00. NO DEFECTS NOTED. CLOSED ALL OPENED FOR GAIN ACCESS. REPLACED IGNITER PLUG WITH NEW. ACCOMPLISHED NORMAL APU START AND RUN. CYCLED APU AIR AND ELEV LEAD SEVERAL TIMES. NO DISCREPANCIES NOTED.