ACR CAPT RPTS LOSING 'A' HYD SYSTEM JUST AFTER LNDG GEAR RETRACTION. FLT CREW DECLARED AN EMER AND RETURNED TO DEP ARPT. ON TAXI IN; 'B' HYD SYSTEM QTY FELL TO 60 PERCENT.

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JUST AFTER GEAR RETRACTION WE EXPERIENCED A COMPLETE LOSS OF 'A' SYSTEM QUANTITY AND PRESSURE. WE CONDUCTED QRH PROCEDURES; DECLARED AN IN-FLIGHT EMERGENCY WITH ATC AND RETURNED AND LANDED AT DEP ARPT. ABOUT 5 MINUTES AFTER LANDING AND APPROACHING GATE AREA; NOSEWHEEL STEERING FAILED (NOSEWHEEL STEERING SWITCH IN ALT AS DIRECTED BY QRH). 'B' SYSTEM QUANTITY WENT TO 60 PERCENT. SINCE WE REQUESTED THAT FIRE RESPONSE FOLLOW US TO THE RAMP AREA; THEY INFORMED US THAT FLUID WAS ACTIVELY COMING OUT OF THE RIGHT MAIN WHEEL WELL. WITH GOOD RESERVE BRAKE PRESSURE; WE SHUT DOWN THE ENGINES AND REQUESTED TO BE TOWED THE REST OF THE WAY TO THE GATE. THE NEXT DAY I CALLED MAINT TO SEE IF THEY HAD DISCOVERED THE REASON FOR THE 'A' SYSTEM FAILURE AND WHY THE NOSEWHEEL STEERING IN ALT FAILED AND 'B' SYSTEM LOSS OF FLUID. AS TO THE 'A' SYSTEM FAILURE; I WAS TOLD THEY FOUND CHAFED LINES; AS TO WHY THE NOSEWHEEL STEERING FAILED WITH ASSOCIATED 'B' FLUID LOSS; THE REPRESENTATIVE ON THE PHONE DIDN'T KNOW. BETTER PERIODIC MAINTENANCE INSPECTIONS OF HYDRAULIC LINES AND COMPONENTS TO FIND CHAFED LINES AND LOOSE OR DAMAGED FITTINGS.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR INDICATES NO FURTHER INFO FROM MAINT AS TO WHY THE 'B' HYD SYSTEM QUANTITY WAS DECREASING. RPTR BELIEVES THE ONLY COMMON AREA FOR BOTH SYSTEMS IS THE NOSEWHEEL STEERING; WHICH USES 'A' SYS FOR NORMAL SOURCE AND 'B' SYS FOR BACKUP; BUT THE LEAK APPEARED TO BE IN THE R MAIN WHEEL WELL.