Narrative:

Climbing out of FL230, I observed an 'a' system low pressure light illumination along with the master caution. I requested to level off at FL250 and it was granted. Upon leveloff, the autoplt was disengaged, at which time I checked the QRH for the 'a' system low pressure illumination. The instructions were to turn the appropriate switch off, which was done. After a short time, the 'a' system pressure gauge needle began to fluctuate back and forth. At this time the QRH was reviewed for an 'a' system failure and the appropriate action was taken. The aircraft flew fine and there were no other problems associated with the aircraft. Maintenance control was notified and the situation reviewed. The WX was good and there was no known turbulence and none forecast for the route from ZZZ1 to ZZZ2. The chief pilot's office was also notified through dispatch, at my request, to make sure they agreed with my decision to continue on to ZZZ1. The aircraft was stable and felt solid on the controls. Aircraft X was hand flown back to ZZZ2 by myself and landed with emergency personnel standing by. The first was also instructed that we were going to treat this as an emergency and that we would be using the brace position for landing. Callback conversation with reporter revealed the following information: the reporter stated when on the ground hydraulic fluid was all over the left side of the aircraft from the main wheel well aft. The reporter said maintenance later advised the loss of 'a' system was caused by a chaffed line in the left wing root aft spar, midway between the wheel well and the left engine. The reporter stated this area cannot be inspected on a preflight check unless the flaps were down and the spoilers extended and locked.

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Original NASA ASRS Text

Title: A B737-200 IN CLB AT FL230 LOST 'A' SYS HYDS PRESSURE AND QUANTITY. CAUSED BY CHAFFED PRESSURE LINE IN L WING ROOT AFT SPAR.

Narrative: CLBING OUT OF FL230, I OBSERVED AN 'A' SYS LOW PRESSURE LIGHT ILLUMINATION ALONG WITH THE MASTER CAUTION. I REQUESTED TO LEVEL OFF AT FL250 AND IT WAS GRANTED. UPON LEVELOFF, THE AUTOPLT WAS DISENGAGED, AT WHICH TIME I CHKED THE QRH FOR THE 'A' SYS LOW PRESSURE ILLUMINATION. THE INSTRUCTIONS WERE TO TURN THE APPROPRIATE SWITCH OFF, WHICH WAS DONE. AFTER A SHORT TIME, THE 'A' SYS PRESSURE GAUGE NEEDLE BEGAN TO FLUCTUATE BACK AND FORTH. AT THIS TIME THE QRH WAS REVIEWED FOR AN 'A' SYS FAILURE AND THE APPROPRIATE ACTION WAS TAKEN. THE ACFT FLEW FINE AND THERE WERE NO OTHER PROBS ASSOCIATED WITH THE ACFT. MAINT CTL WAS NOTIFIED AND THE SIT REVIEWED. THE WX WAS GOOD AND THERE WAS NO KNOWN TURB AND NONE FORECAST FOR THE RTE FROM ZZZ1 TO ZZZ2. THE CHIEF PLT'S OFFICE WAS ALSO NOTIFIED THROUGH DISPATCH, AT MY REQUEST, TO MAKE SURE THEY AGREED WITH MY DECISION TO CONTINUE ON TO ZZZ1. THE ACFT WAS STABLE AND FELT SOLID ON THE CTLS. ACFT X WAS HAND FLOWN BACK TO ZZZ2 BY MYSELF AND LANDED WITH EMER PERSONNEL STANDING BY. THE FIRST WAS ALSO INSTRUCTED THAT WE WERE GOING TO TREAT THIS AS AN EMER AND THAT WE WOULD BE USING THE BRACE POS FOR LNDG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED WHEN ON THE GND HYD FLUID WAS ALL OVER THE L SIDE OF THE ACFT FROM THE MAIN WHEEL WELL AFT. THE RPTR SAID MAINT LATER ADVISED THE LOSS OF 'A' SYS WAS CAUSED BY A CHAFFED LINE IN THE L WING ROOT AFT SPAR, MIDWAY BTWN THE WHEEL WELL AND THE L ENG. THE RPTR STATED THIS AREA CANNOT BE INSPECTED ON A PREFLT CHK UNLESS THE FLAPS WERE DOWN AND THE SPOILERS EXTENDED AND LOCKED.

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.