Narrative:

During taxi out from gate; we were given instructions by ground control to taxi to runway xxr via X hold short xy for a 20 min wheels-up time to ZZZ1. Once the brakes were set at xy; I decided to do the flight control check. As I pulled up the lower EICAS screen to display the flight controls; that was the same time we observed the right hydraulic quantity display at .24 and the PF symbol next to it. We then got the right hydraulic quantity and right hydraulic reservoir EICAS message. I directed my first officer to contact maintenance control and I ran the appropriate checklist. The B757 hydraulic system pressure-right (only). This directed us to shutoff both the engine and electric hydraulic pumps for that side. I made a decision that we should be towed back to the gate as we now lost our normal brakes (right hydraulic system) and we were now on the alternate brakes (left hydraulic system). APU was started and we shut down the engines. Ground control was informed of the problem. Ground control sent the department of aviation out to inspect the aircraft. They confirmed a fluid leak and ground control dispatched the fire department. Maintenance arrived with a spill kit and began a clean-up. We were towed back to our original gate where maintenance started their inspection. It was found that an antiskid valve was cracked. A new one was installed and the system replenished; tested; and released for flight. No other problems were noted and our flight was completed to ZZZ1.

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Original NASA ASRS Text

Title: A B757-200 FLT CREW TAXIING FOR TAKEOFF NOTED AN EICAS MESSAGE R HYD QTY. THEY FOLLOWED CHECKLIST; COORDINATED WITH MAINT; AND WERE TOWED BACK TO GATE.

Narrative: DURING TAXI OUT FROM GATE; WE WERE GIVEN INSTRUCTIONS BY GND CTL TO TAXI TO RWY XXR VIA X HOLD SHORT XY FOR A 20 MIN WHEELS-UP TIME TO ZZZ1. ONCE THE BRAKES WERE SET AT XY; I DECIDED TO DO THE FLT CTL CHK. AS I PULLED UP THE LOWER EICAS SCREEN TO DISPLAY THE FLT CTLS; THAT WAS THE SAME TIME WE OBSERVED THE R HYD QUANTITY DISPLAY AT .24 AND THE PF SYMBOL NEXT TO IT. WE THEN GOT THE R HYD QUANTITY AND R HYD RESERVOIR EICAS MESSAGE. I DIRECTED MY FO TO CONTACT MAINT CTL AND I RAN THE APPROPRIATE CHKLIST. THE B757 HYD SYS PRESSURE-R (ONLY). THIS DIRECTED US TO SHUTOFF BOTH THE ENG AND ELECTRIC HYD PUMPS FOR THAT SIDE. I MADE A DECISION THAT WE SHOULD BE TOWED BACK TO THE GATE AS WE NOW LOST OUR NORMAL BRAKES (R HYD SYS) AND WE WERE NOW ON THE ALTERNATE BRAKES (L HYD SYS). APU WAS STARTED AND WE SHUT DOWN THE ENGS. GND CTL WAS INFORMED OF THE PROB. GND CTL SENT THE DEPT OF AVIATION OUT TO INSPECT THE ACFT. THEY CONFIRMED A FLUID LEAK AND GND CTL DISPATCHED THE FIRE DEPT. MAINT ARRIVED WITH A SPILL KIT AND BEGAN A CLEAN-UP. WE WERE TOWED BACK TO OUR ORIGINAL GATE WHERE MAINT STARTED THEIR INSPECTION. IT WAS FOUND THAT AN ANTISKID VALVE WAS CRACKED. A NEW ONE WAS INSTALLED AND THE SYS REPLENISHED; TESTED; AND RELEASED FOR FLT. NO OTHER PROBS WERE NOTED AND OUR FLT WAS COMPLETED TO ZZZ1.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.