As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IND - FLT 531 - AT CRUISE, HYDRAULIC QUANTITY ON A-SYSTEM DROPPED TO SLIGHTLY BELOW ONE GALLON. PILOT DIVERTED TO INDIANAPOLIS AIRPORT. NR 2 ENGINE DRIVEN HYDRAULIC CASE DRAIN FILTER BACK-UP RING WAS FOUND UNSEATED. REPLACED O-RING AND BACK-UP RINGS, RUN TESTED, NO LEAKS NOTED.