A B737-200 returned to the field due to loss of 'B' system hydraulic fluid.

Attributes
ACN	363173
Time
Date	199703
Day	Sat
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : zzz
State Reference	US
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Light	Night
Aircraft 1
Controlling Facilities	tower : clt
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Flight Phase	other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	363173
Person 2
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
Events
Anomaly	aircraft equipment problem : less severe non adherence : published procedure other anomaly other
Independent Detector	other flight crewa other other : unspecified cockpit
Resolutory Action	flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

On mar/xx/97 I and avionics technician abc undertook the task of troubleshooting an autoplt problem on a B737-200. This was accomplished at the gate from XA00 to XC30. After several checks we decided to change the 'B' system aileron PCU xfer valve. Abc held the flashlight while I did the work. The valve was installed per B737-200 maintenance manual. The PCU xfer valve leak check was good, but the autoplt remained inoperative on 'B' system. We decided to leave the xfer valve in the aircraft due to time factor and for precautionary reasons. The autoplt remained on MEL. On mar/xx/97 other mechanics in ZZZ replaced the 'B' system PCU shutoff valve and this fixed the autoplt. When the aircraft departed ZZZ on climb out it suffered hydraulic failure due to loss of 'B' system fluid. The cause was found to be that the xfer valve I had installed still had a shipping gasket on it. This is not a plastic cap but a rubber black seal (with holes in it) over the seal plate. I knew this was on the valve, but at the time I did not know it was to be removed -- especially when the old valve was installed with one also. This led me to believe installation without it would sacrifice the unit's integrity. The maintenance manual and ipc were not very clear.

Original NASA ASRS Text

Title: A B737-200 RETURNED TO THE FIELD DUE TO LOSS OF 'B' SYS HYD FLUID.

Narrative: ON MAR/XX/97 I AND AVIONICS TECHNICIAN ABC UNDERTOOK THE TASK OF TROUBLESHOOTING AN AUTOPLT PROB ON A B737-200. THIS WAS ACCOMPLISHED AT THE GATE FROM XA00 TO XC30. AFTER SEVERAL CHKS WE DECIDED TO CHANGE THE 'B' SYS AILERON PCU XFER VALVE. ABC HELD THE FLASHLIGHT WHILE I DID THE WORK. THE VALVE WAS INSTALLED PER B737-200 MAINT MANUAL. THE PCU XFER VALVE LEAK CHK WAS GOOD, BUT THE AUTOPLT REMAINED INOP ON 'B' SYS. WE DECIDED TO LEAVE THE XFER VALVE IN THE ACFT DUE TO TIME FACTOR AND FOR PRECAUTIONARY REASONS. THE AUTOPLT REMAINED ON MEL. ON MAR/XX/97 OTHER MECHS IN ZZZ REPLACED THE 'B' SYS PCU SHUTOFF VALVE AND THIS FIXED THE AUTOPLT. WHEN THE ACFT DEPARTED ZZZ ON CLBOUT IT SUFFERED HYD FAILURE DUE TO LOSS OF 'B' SYS FLUID. THE CAUSE WAS FOUND TO BE THAT THE XFER VALVE I HAD INSTALLED STILL HAD A SHIPPING GASKET ON IT. THIS IS NOT A PLASTIC CAP BUT A RUBBER BLACK SEAL (WITH HOLES IN IT) OVER THE SEAL PLATE. I KNEW THIS WAS ON THE VALVE, BUT AT THE TIME I DID NOT KNOW IT WAS TO BE REMOVED -- ESPECIALLY WHEN THE OLD VALVE WAS INSTALLED WITH ONE ALSO. THIS LED ME TO BELIEVE INSTALLATION WITHOUT IT WOULD SACRIFICE THE UNIT'S INTEGRITY. THE MAINT MANUAL AND IPC WERE NOT VERY CLR.

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.