As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD-LGA - FLT 6492 - AFTER TAKEOFF, THE LEFT HYDRAULIC PRESSURE DROPPED TO ZERO WITH NO LOSS OF HYDRAULIC QTY. THE AIRCRAFT RETURNED TO THE FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE LEFT ENGINE DRIVEN HYDRAULIC PUMP. (M)