What was found
WHEN THROTTLES RETARDED FOR DESCENT A STRANGE ODOR IS DETECTED FOLLOWED BY A HAZE. THEN A SHORT BURST OF SMOKE. LEFT AND RIGHT PACK TEMPS 40 DEGREES. ADVANCED AND RETARDED 1 AND 3 THROTTLES. MORE SMOKE APPEARED AFTER NR 1 THROTTLE ADVANCED AND RETARDED. MAINTENANCE FOUND A DEFECTIVE HYDRAULIC PRESSURIZATION CHECK VALVE LEAKING HYDRAULIC FLUID INTO THE NR 1 13 STAGE BLEED DUCT. THE CHECK VALVE WAS REPLACED, THE 13 STAGE BLEED VALVE, BLEED VALVE CONTROLLER AND THE HIGH PRESSURE SHUTOFF VALVES WERE ALSO REPLACED DUE TO CONTAMINATION.