Narrative:

All operations were normal until pushback from gate. After pushback (XX28Z) on aug/xa/98, flight XXX, den-okc, when the captain set the parking brake to begin the start sequence, he noted the brake accumulator pressure indicator dropped to 2300 psi. We (crew) conferred with air carrier maintenance and talked with air carrier maintenance individual there about problem. Their advice was to return (via tug) to gate, have aircraft chocked, turn off 'hydraulic B' pumps, and pump brakes to deplete residual pressure and then check indicator for residual pressure. (We accomplished these items.) if indicator remained above 1000 psi, then maintenance stated that accumulator pressure was normal, and 'B' pumps could be turned back on. If indicator indicated normal range (greater than or equal to 3000 psi) with 'B' pump on, then nothing was wrong and we could continue. Maintenance also wanted to talk to gate mechanic and explain situation on phone. Captain performed prescribed actions -- pressure indicated 975 psi until 'B' pumps were turned back on, then 3100 psi. Gate mechanic returned from kiosk and cleared us to pushback again. (Maintenance had terminated radio patch.) made entry in logbook addressing problem and 'ok to continue per maintenance controller' with captain's name, and continued trip uneventfully. Upon return to den (after okc leg), mechanics informed captain we may have needed deferral on the item. In the future, a second call to maintenance controller after corrective actions were taken would confirm status, although first contact gave definite impression we would be good to continue. Also, could have had maintenance technicians perform troubleshooting vice crew. Eliminates one potential communication problem. Supplemental information from acn 410926: maintenance was contacted, and the crew was given a procedure to help maintenance resolve the problem. The purpose of the procedure was to check system reliability for leaks and accumulator precharge. Nothing abnormal was found. In the process of troubleshooting the problem, the brake pressure indicator returned to normal. All this information was given to maintenance who was in contact with local maintenance. Communication with line maintenance provided no indication to preclude a continuation of the flight, and that any further action was required. The flight departed. Documentation by maintenance was not completed. It is felt that the communication link between aircraft maintenance and local line maintenance in this case was weak. Information needed by the crew was not provided. The crew believed the flight could depart since local maintenance cleared the flight for pushback. Supplemental information from acn 411297: in hindsight, we should have called maintenance again to confirm we were cleared to dispatch. Another option would have been to insist on a new maintenance release from the mechanic. A breakdown in communication occurred between the aircraft crew, maintenance, and the local mechanic pushing us back. Assume nothing!

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Original NASA ASRS Text

Title: B727 CREW WAS GIVEN AN 'OK TO CONTINUE' ON A HYD BRAKE PROB.

Narrative: ALL OPS WERE NORMAL UNTIL PUSHBACK FROM GATE. AFTER PUSHBACK (XX28Z) ON AUG/XA/98, FLT XXX, DEN-OKC, WHEN THE CAPT SET THE PARKING BRAKE TO BEGIN THE START SEQUENCE, HE NOTED THE BRAKE ACCUMULATOR PRESSURE INDICATOR DROPPED TO 2300 PSI. WE (CREW) CONFERRED WITH ACR MAINT AND TALKED WITH ACR MAINT INDIVIDUAL THERE ABOUT PROB. THEIR ADVICE WAS TO RETURN (VIA TUG) TO GATE, HAVE ACFT CHOCKED, TURN OFF 'HYD B' PUMPS, AND PUMP BRAKES TO DEPLETE RESIDUAL PRESSURE AND THEN CHK INDICATOR FOR RESIDUAL PRESSURE. (WE ACCOMPLISHED THESE ITEMS.) IF INDICATOR REMAINED ABOVE 1000 PSI, THEN MAINT STATED THAT ACCUMULATOR PRESSURE WAS NORMAL, AND 'B' PUMPS COULD BE TURNED BACK ON. IF INDICATOR INDICATED NORMAL RANGE (GREATER THAN OR EQUAL TO 3000 PSI) WITH 'B' PUMP ON, THEN NOTHING WAS WRONG AND WE COULD CONTINUE. MAINT ALSO WANTED TO TALK TO GATE MECH AND EXPLAIN SIT ON PHONE. CAPT PERFORMED PRESCRIBED ACTIONS -- PRESSURE INDICATED 975 PSI UNTIL 'B' PUMPS WERE TURNED BACK ON, THEN 3100 PSI. GATE MECH RETURNED FROM KIOSK AND CLRED US TO PUSHBACK AGAIN. (MAINT HAD TERMINATED RADIO PATCH.) MADE ENTRY IN LOGBOOK ADDRESSING PROB AND 'OK TO CONTINUE PER MAINT CTLR' WITH CAPT'S NAME, AND CONTINUED TRIP UNEVENTFULLY. UPON RETURN TO DEN (AFTER OKC LEG), MECHS INFORMED CAPT WE MAY HAVE NEEDED DEFERRAL ON THE ITEM. IN THE FUTURE, A SECOND CALL TO MAINT CTLR AFTER CORRECTIVE ACTIONS WERE TAKEN WOULD CONFIRM STATUS, ALTHOUGH FIRST CONTACT GAVE DEFINITE IMPRESSION WE WOULD BE GOOD TO CONTINUE. ALSO, COULD HAVE HAD MAINT TECHNICIANS PERFORM TROUBLESHOOTING VICE CREW. ELIMINATES ONE POTENTIAL COM PROB. SUPPLEMENTAL INFO FROM ACN 410926: MAINT WAS CONTACTED, AND THE CREW WAS GIVEN A PROC TO HELP MAINT RESOLVE THE PROB. THE PURPOSE OF THE PROC WAS TO CHK SYS RELIABILITY FOR LEAKS AND ACCUMULATOR PRECHARGE. NOTHING ABNORMAL WAS FOUND. IN THE PROCESS OF TROUBLESHOOTING THE PROB, THE BRAKE PRESSURE INDICATOR RETURNED TO NORMAL. ALL THIS INFO WAS GIVEN TO MAINT WHO WAS IN CONTACT WITH LCL MAINT. COM WITH LINE MAINT PROVIDED NO INDICATION TO PRECLUDE A CONTINUATION OF THE FLT, AND THAT ANY FURTHER ACTION WAS REQUIRED. THE FLT DEPARTED. DOCUMENTATION BY MAINT WAS NOT COMPLETED. IT IS FELT THAT THE COM LINK BTWN ACFT MAINT AND LCL LINE MAINT IN THIS CASE WAS WEAK. INFO NEEDED BY THE CREW WAS NOT PROVIDED. THE CREW BELIEVED THE FLT COULD DEPART SINCE LCL MAINT CLRED THE FLT FOR PUSHBACK. SUPPLEMENTAL INFO FROM ACN 411297: IN HINDSIGHT, WE SHOULD HAVE CALLED MAINT AGAIN TO CONFIRM WE WERE CLRED TO DISPATCH. ANOTHER OPTION WOULD HAVE BEEN TO INSIST ON A NEW MAINT RELEASE FROM THE MECH. A BREAKDOWN IN COM OCCURRED BTWN THE ACFT CREW, MAINT, AND THE LCL MECH PUSHING US BACK. ASSUME NOTHING!

Data retrieved from NASA's ASRS site as of July 2007 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.