A B737-200 returned to the field due to loss of hydraulic pressure and quantity caused by an incorre...

Attributes
ACN	363622
Time
Date	199703
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz
State Reference	US
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Flight Phase	other
Flight Plan	None
Person 1
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	363622
Person 2
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	363278
Events
Anomaly	aircraft equipment problem : critical non adherence : far non adherence : published procedure other anomaly other
Independent Detector	other flight crewa other other : unspecified cockpit
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

A mechanic and I were working on autoplt problem for air carrier xyz aircraft. This was a continuing problem and an aileron PCU xfer valve had been changed already. Mechanic had troubleshot the problem to an aileron autoplt solenoid valve. We got a copy of the maintenance manual for removal and replacement of the valve and headed for the aircraft. My part of the task of replacing the solenoid was limited to taking the necessary safety precautions by depressurizing the hydraulic system, pulling circuit breakers and placing inoperative tags on the proper switches and so forth according to the B737 maintenance manual. When I came back down, mechanic had the solenoid changed. There was skydrol everywhere and mechanic was soaked, so I said I would finish up by lockwiring the mount bolts. Next, I went and performed an operational test of the solenoid per maintenance manual. The system checked out satisfactorily. Then I went down into the wheel well to look for leaks and make sure the area was clear of tools. I did not see any leaks at this time. When the aircraft took off and autoplt was selected on the solenoid valve that now worked allowed hydraulic fluid to the xfer valve. The xfer valve had an incorrect gasket on it and allowed the hydraulic fluid to leak out and the aircraft returned to field.

Original NASA ASRS Text

Title: A B737-200 RETURNED TO THE FIELD DUE TO LOSS OF HYD PRESSURE AND QUANTITY CAUSED BY AN INCORRECT GASKET INSTALLED ON THE AILERON PWR UNIT XFER VALVE.

Narrative: A MECH AND I WERE WORKING ON AUTOPLT PROB FOR ACR XYZ ACFT. THIS WAS A CONTINUING PROB AND AN AILERON PCU XFER VALVE HAD BEEN CHANGED ALREADY. MECH HAD TROUBLESHOT THE PROB TO AN AILERON AUTOPLT SOLENOID VALVE. WE GOT A COPY OF THE MAINT MANUAL FOR REMOVAL AND REPLACEMENT OF THE VALVE AND HEADED FOR THE ACFT. MY PART OF THE TASK OF REPLACING THE SOLENOID WAS LIMITED TO TAKING THE NECESSARY SAFETY PRECAUTIONS BY DEPRESSURIZING THE HYD SYS, PULLING CIRCUIT BREAKERS AND PLACING INOP TAGS ON THE PROPER SWITCHES AND SO FORTH ACCORDING TO THE B737 MAINT MANUAL. WHEN I CAME BACK DOWN, MECH HAD THE SOLENOID CHANGED. THERE WAS SKYDROL EVERYWHERE AND MECH WAS SOAKED, SO I SAID I WOULD FINISH UP BY LOCKWIRING THE MOUNT BOLTS. NEXT, I WENT AND PERFORMED AN OPERATIONAL TEST OF THE SOLENOID PER MAINT MANUAL. THE SYS CHKED OUT SATISFACTORILY. THEN I WENT DOWN INTO THE WHEEL WELL TO LOOK FOR LEAKS AND MAKE SURE THE AREA WAS CLR OF TOOLS. I DID NOT SEE ANY LEAKS AT THIS TIME. WHEN THE ACFT TOOK OFF AND AUTOPLT WAS SELECTED ON THE SOLENOID VALVE THAT NOW WORKED ALLOWED HYD FLUID TO THE XFER VALVE. THE XFER VALVE HAD AN INCORRECT GASKET ON IT AND ALLOWED THE HYD FLUID TO LEAK OUT AND THE ACFT RETURNED TO FIELD.

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.

A B737-200 returned to the field due to loss of hydraulic pressure and quantity caused by an incorrect gasket installed on the aileron power unit xfer valve.