What was found
DURING TAKEOFF, THE RIGHT MAIN GEAR DID NOT RETRACT AND HAD AN A-SYSTEM HYDRAULIC FAILURE, QUANTITY WENT TO ZERO. MANUALLY EXTENDED LEFT MAIN AND NOSE GEAR. AIRCRAFT RETURNED TO LGA AND LANDED WITHOUT INCIDENT. REPLACED THE LEFT MAIN GEAR SEQUENCE LOCK. JACKED AIRCRAFT AND CYCLED MAIN AND NOSE GEAR. LEAK AND OPERATIONAL CHECK OK.