What was found
IN CRUISE FLIGHT AT 800 FT AGL, THE HYDRAULIC PACK SWITCHED FROM SYSTEM NR 1 TO SYSTEM NR 2. THE COLLECTIVE BOTTOMED OUT ON THE LOWER STOP, PUTTING THE AIRCRAFT NOSE DOWN. THE AIRCRAFT IMMEDIATELY LOST 200 FEET OF ALTITUDE. PILOT REPORTED HYD BLOCK LIGHT ON FIRST, FOLLOWED BY HYD 1 AND HYD 2 LIGHTS FOR ABOUT 3 TO 4 SECONDS BEFORE BOTH EXTINGUISHED. HYD BLOCK REMAINED ILLUMINATED. LANDING AT NEARBY AIRPORT WAS NORMAL. HYDRAULIC PACK WAS REMOVED AND SENT TO MANUFACTURER FOR EVALUATION.