What was found
FLT 959 - GUM - LOST SYSTEM 'A' HYDRAULIC PRESSURE WHILE LOWERING FLAPS, NR 4 LE SLAT DID NOT DEPLOY. COMPLIED WITH EMERGENCY PROCEDURES AS PER FLIGHT MANUAL. REMOVED AND REPLACED NR 4 LE SLAT ACTUATOR. CHECKED BOTH ENGINE CASE DRAIN FILTER MAGNETIC PLUGS, FOUND METAL PARTICLES. REPLACED NR 1 AND NR 2 ENGINE DRIVEN HYDRAULIC PUMPS DUE TO SUSPECTED FAILURE. PERFORMED LEAK AND OPERATIONAL CHECK ON ENGINE RUN AND ALL INDICATIONS NORMAL. (M)