What was found
WHILE CRUISING AT 22,000 FT, PILOT EXPERIENCED HYD AUTO PRESSURE FLUCTUATION BETWEEN 1600/3200. HYD ON, PRESSURE FLUCTUATIONS AND SPIKES TO 3800. HYD OFF, PRESS 0 AND LANDING GEAR FALLS OUT. PILOT LANDED WITH HYD PRESSURE ON AND SEEING PRESSURE FLUCTUATIONS AND SPIKES TO 3800. ALSO DURING PRESSURE FLUCTUATIONS, THUMPING/BUMPING NOISE/VIBRATION AT PILOT FLOOR - FORWARD. INVESTIGATION DISCLOSED THE HYDRAULIC PUMP FAILED. HYDRAULIC POWER PACK VENTILATION FAN WAS ALSO FOUND FAILED. REPLACED FAULTY COMPONENTS; OPERATIONAL CHECKS WERE SATISFACTORY.