What was found
THE RIGHT ENGINE HYDRAULIC PUMP FAILED SOON AFTER TAKE OFF. THE LANDING GEAR FAILED TO RETRACT FULLY. THE PILOT TRIED SEVERAL TIMES TO EXTEND THE LANDING GEAR, AND FINALLY MANAGED TO GET THEM ALL IN A SAFE DOWN AND LOCKED POSITION, TO MAKE A LANDING. UPON INVESTIGATION, IT WAS FOUND THAT THE HYDRAULIC PUMP DRIVE SHAFT SEAL WAS BROKEN. THIS WAS CAUSED BY A VALVE INSIDE THE PUMP THAT WAS STUCK IN THE OPEN POSITION, AND ALLOWED THE HYDRAULIC FLUID TO BE PUMPED OVERBOARD. PUMP MAY NOT HAVE BEEN CORRECTLY TESTED BY THE OVERHAULER.