What was found
UPON GEAR RETRACTION, PILOT NOTICED GEAR UNSAFE LIGHT, GEAR WOULD NOT EXTEND, HAND PUMP TRIED, NO PRESSURE, CO2 BOTTLE PULLED, HYDRAULIC POWER PACK COVER LIFTED AND CAUSED FLUID TO LEAK OVER INTO COCKPIT FLOOR, AIRCRAFT LANDED GEAR UP WITH MINOR DAMAGE, HYDRAULIC POWER PACK DISASSEMBLED AND FOUND HOLD DOWN PLATES (PN 31886-02, 03) CRACKED ALLOWING RELIEF VALVE BODY TO UNSEAT SO NO HYDRAULIC PRESSURE COULD BE ROUTED TO SYSTEM, A POWER PACK REBUILD SHOP SAID THIS IS A COMMON PROBLEM.