What was found
DURING A ROUTINE INSP OF THE AIRCRAFT, FOUND THE IN-LINE AIR FILTER TO THE SECONDARY PRESSURE SYSTEM HAD BEEN HEATED BY THE EXHAUST SYSTEM ON THE LEFT EXHAUST. THE CLEAR PLASTIC MELTED THEN SHATTERED IN PIECES. SUBMITTER STATED THIS COULD CAUSE SMALL PIECES TO GET INTO THE INSTRUMENT AIR SYSTEM. AIRBORNE PRODUCTS MAKES AN IN-LINE AIR FILTER MADE OUT OF A METAL CANISTER. THIS FILTER WAS USED PREVIOUSLY ON THE AIRCRAFT WITHOUT HAVING ANY DISCREPANCIES.