What was found
FLT 883 CLT-CUN - BURNING SMELL - CREW REPORTED A STRONG, ACRID BURNING SMELL IN COCKPIT ON DESCENT FROM 4500FT - 2500FT AGL AND DURING SHUTDOWN AT GATE. MAINTENANCE TESTED THE AVIONICS EXTRACT FAN IAW AIRBUS MAINTENANCE MANUAL 21-26-00 WITH NO FAULTS FOUND. NO CONTAMINATION FOUND IN LT OR RT PACKS. INSPECTED ENGINES - NO LEAKS OR DUCT CONTAMINATION PRESENT. MAINTENANCE COMPLIED WITH ENVIRONMENTAL CONTROL SYSTEM DECONTAMINATION PROCEDURES.