As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 3551. 'L HYD QTY' MESSAGE DISPLAYED AFTER TAKEOFF. THE LEFT HYDRAULIC QUANTITY DECREASED RAPIDLY. INTERRUPTED THE FLIGHT AND EXTENDED LANDING GEAR WITH STANDBY SYSTEM. TOWED TO PARKING APRON AFTER LANDING. CHECK FOUND THE HYDRAULIC DUCT FOR LT LANDING GEAR DOWNLOCK ACTUATOR BROKEN. REPLACED THE DUCT. OKAY.