MLG HAS HYD SYS MALFUNCTION INDICATION DURING CRUISE AND THE FLC WERE ABLE TO RESTORE THE SYS TO NORMAL. INITIAL FIRST STEP SELECTED WAS INAPPROPRIATE.

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SUBJECT: R HYD SYS FAILURE. AUG/XX/94 FLT PHX TO JFK; ACFT (MD82) AT CRUISE ALT FL330 A 'R REVERSE ACCUMULATOR LOW LIGHT' CAME. FOLLOWING THE NON-NORMAL PROC WE PLACED THE HYD PUMP CTL SWITCH TO 'HI.' AT THAT THE QUANTITY GAUGE DROPPED TO ZERO. THE PRESSURE DROPPED TO ZERO AND ALL RELATED SYS LIGHTS CAME ON. I CALLED FOR THE HYD FLUID LOSS CHKLIST FOLLOWED BY THE R HYD SYS FAIL CHKLIST. ON FURTHER OBSERVATION THE FO AND I NOTED THE QUANTITY GAUGE HAD A NEGATIVE VALUE AND WAS POINTING ALMOST TO THE 19 QUART LEVEL. I CALLED THE MCI MAINT COORDINATOR MD80. HE SAID THAT IT SOUNDED LIKE A GAUGE SERVO FAILURE; BUT THAT WOULD NOT EXPLAIN THE LOSS OF PRESSURE. NOT KNOWING WHERE MY FLUID WAS FOR SURE I ASKED THE FO TO RETURN THE HYD PUMP CTL SWITCH TO THE LOW POS. AT THIS TIME THE QUANTITY AND THE PRESSURE RETURNED TO NORMAL. AFTER A REASONABLE TIME WE RESET ALL FLT CTLS TO THEIR NORMAL POS. LNDG AND TAXI IN WAS NORMAL. NO FURTHER FLUID LOSS WAS NOTED. I SUSPECT WE MAY HAVE HAD AIR IN THE SYS AND SOMEHOW WE PURGED IT OUT.