Narrative:

I flew to ZZZ; which was uneventful. Upon arrival in ZZZ; I conducted my preflight duties for our return to ZZZ1. On the walk around inspection; I noticed a 'black thing' hanging out of the left main gear bay about 2 inches. I first thought it was a piece of rubber from the seal around the gear bay. After closer examination; I determined that in fact it was actually a flag that was connected to a pin. The flag was quite tattered and very discolored. I asked the ground crew if they had pinned anything in the main gear bay. They answered no. So; I checked the logbook to make sure nothing was MEL'd or placarded inoperative. Nothing was in the logbook so I requested maintenance to come out to the aircraft. The contract mechanic told me on the first examination; that the flag was connected to a pin and a 'collar or lockout device' of some sort. He said that he needed to contact maintenance control to see what exactly it was. After some time they discovered that it was a lockout device for the power transfer unit which is used to operate the flaps/slats when the system B engine-driven hydraulic pump volume is lost. The only write up in the logbook that involved hydraulics was for the thrust reversers from a few days earlier. After discussion between the contract mechanic; the mechanic in maintenance control; and the captain; I believe that they all determined that no write up was needed in the logbook. We departed normally with only a short delay. The rest of the flight was uneventful. The only explanation I can give for not seeing the flag on the walkaround in ZZZ1 is this: I believe that the extremely discolored flag had been blown up and had tangled or wrapped itself around the other components of the gear well on the previous flts. Upon landing in ZZZ1; the wind from the landing had 'blown' the flag partially down; allowing me to notice it. On all of my preflts; I always visually inspect the main landing gear bays for any fluid leaks; damage; or anything out of the ordinary.callback conversation with reporter 690456 revealed the following information: the reporter stated that a 2 inch wide; dirty; black seal was flapping in the landing gear well. On investigating; it was a 'remove before flight' lockout flag attached to a component in the wheel well on the center keel beam. Reporter advised the captain and contacted maintenance to determine what was locked out. The line maintenance controller had no record of any deferred items or work recently performed that would require this unit to be locked out. The reporter indicated that there is no routine check that is performed by the crew on this unit. This unit is a safety of flight item as failure or low pressure on the 'B' engine driven hydraulic pump will ensure full autoslat operation.supplemental information from reporter 692294: after talking with mr X in ZZZ1; contacted maintenance; and looking at the pictures that had been sent also with the numbers off the electrical plug; we concluded that the standby hydraulic module was the valve with the lock left in place. After removing and operations checking all systems; I told mr Y to sign the logbook as required. They were not going to make a logbook entry for this. With that I forwarded all this information to my manager. It is my understanding that my manager passed this on to regulatory affairs.callback conversation with reporter 692294 revealed the following information: the reporter worked with the contract technician at the station to get pictures; part numbers and other information on the component that had the flag. The reporter indicated the component was identified as the automatic slat valve on the standby hydraulic module and the lock and flag were removed. This flag and valve lock is normally installed when entering a dock for heavy maintenance to prevent the leading edge devices from being deployed; damaging open engine cowling. The procedure is on a docking and deducing job card and requires a signoff and is an inspector buyback item. This airplane somehow got out of the check and entered service where it was discovered in a non maintenance station. A contract maintenance technician tested the standby hydraulic system operation and checked ok andwas instructed to sign off the crew log report. The flight crew did not make a log input and it appeared no log report was entered. The reporter turned all information on this incident to the department manager.

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Original NASA ASRS Text

Title: A B737-800 WAS DISPATCHED AND OPERATED FOR SEVERAL DAYS WITH THE HYDRAULIC POWER XFER UNIT LOCKED OUT. LOCKOUT VALVE PINNED WITH FLAG.

Narrative: I FLEW TO ZZZ; WHICH WAS UNEVENTFUL. UPON ARR IN ZZZ; I CONDUCTED MY PREFLT DUTIES FOR OUR RETURN TO ZZZ1. ON THE WALK AROUND INSPECTION; I NOTICED A 'BLACK THING' HANGING OUT OF THE LEFT MAIN GEAR BAY ABOUT 2 INCHES. I FIRST THOUGHT IT WAS A PIECE OF RUBBER FROM THE SEAL AROUND THE GEAR BAY. AFTER CLOSER EXAMINATION; I DETERMINED THAT IN FACT IT WAS ACTUALLY A FLAG THAT WAS CONNECTED TO A PIN. THE FLAG WAS QUITE TATTERED AND VERY DISCOLORED. I ASKED THE GND CREW IF THEY HAD PINNED ANYTHING IN THE MAIN GEAR BAY. THEY ANSWERED NO. SO; I CHKED THE LOGBOOK TO MAKE SURE NOTHING WAS MEL'D OR PLACARDED INOP. NOTHING WAS IN THE LOGBOOK SO I REQUESTED MAINT TO COME OUT TO THE ACFT. THE CONTRACT MECHANIC TOLD ME ON THE FIRST EXAMINATION; THAT THE FLAG WAS CONNECTED TO A PIN AND A 'COLLAR OR LOCKOUT DEVICE' OF SOME SORT. HE SAID THAT HE NEEDED TO CONTACT MAINT CTL TO SEE WHAT EXACTLY IT WAS. AFTER SOME TIME THEY DISCOVERED THAT IT WAS A LOCKOUT DEVICE FOR THE POWER TRANSFER UNIT WHICH IS USED TO OPERATE THE FLAPS/SLATS WHEN THE SYSTEM B ENG-DRIVEN HYDRAULIC PUMP VOLUME IS LOST. THE ONLY WRITE UP IN THE LOGBOOK THAT INVOLVED HYDRAULICS WAS FOR THE THRUST REVERSERS FROM A FEW DAYS EARLIER. AFTER DISCUSSION BETWEEN THE CONTRACT MECHANIC; THE MECHANIC IN MAINT CTL; AND THE CAPT; I BELIEVE THAT THEY ALL DETERMINED THAT NO WRITE UP WAS NEEDED IN THE LOGBOOK. WE DEPARTED NORMALLY WITH ONLY A SHORT DELAY. THE REST OF THE FLT WAS UNEVENTFUL. THE ONLY EXPLANATION I CAN GIVE FOR NOT SEEING THE FLAG ON THE WALKAROUND IN ZZZ1 IS THIS: I BELIEVE THAT THE EXTREMELY DISCOLORED FLAG HAD BEEN BLOWN UP AND HAD TANGLED OR WRAPPED ITSELF AROUND THE OTHER COMPONENTS OF THE GEAR WELL ON THE PREVIOUS FLTS. UPON LNDG IN ZZZ1; THE WIND FROM THE LNDG HAD 'BLOWN' THE FLAG PARTIALLY DOWN; ALLOWING ME TO NOTICE IT. ON ALL OF MY PREFLTS; I ALWAYS VISUALLY INSPECT THE MAIN LNDG GEAR BAYS FOR ANY FLUID LEAKS; DAMAGE; OR ANYTHING OUT OF THE ORDINARY.CALLBACK CONVERSATION WITH RPTR 690456 REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT A 2 INCH WIDE; DIRTY; BLACK SEAL WAS FLAPPING IN THE LNDG GEAR WELL. ON INVESTIGATING; IT WAS A 'REMOVE BEFORE FLT' LOCKOUT FLAG ATTACHED TO A COMPONENT IN THE WHEEL WELL ON THE CENTER KEEL BEAM. RPTR ADVISED THE CAPT AND CONTACTED MAINT TO DETERMINE WHAT WAS LOCKED OUT. THE LINE MAINT CTLR HAD NO RECORD OF ANY DEFERRED ITEMS OR WORK RECENTLY PERFORMED THAT WOULD REQUIRE THIS UNIT TO BE LOCKED OUT. THE RPTR INDICATED THAT THERE IS NO ROUTINE CHK THAT IS PERFORMED BY THE CREW ON THIS UNIT. THIS UNIT IS A SAFETY OF FLT ITEM AS FAILURE OR LOW PRESSURE ON THE 'B' ENG DRIVEN HYDRAULIC PUMP WILL ENSURE FULL AUTOSLAT OPERATION.SUPPLEMENTAL INFO FROM RPTR 692294: AFTER TALKING WITH MR X IN ZZZ1; CONTACTED MAINT; AND LOOKING AT THE PICTURES THAT HAD BEEN SENT ALSO WITH THE NUMBERS OFF THE ELECTRICAL PLUG; WE CONCLUDED THAT THE STANDBY HYD MODULE WAS THE VALVE WITH THE LOCK LEFT IN PLACE. AFTER REMOVING AND OPS CHKING ALL SYSTEMS; I TOLD MR Y TO SIGN THE LOGBOOK AS REQUIRED. THEY WERE NOT GOING TO MAKE A LOGBOOK ENTRY FOR THIS. WITH THAT I FORWARDED ALL THIS INFO TO MY MANAGER. IT IS MY UNDERSTANDING THAT MY MANAGER PASSED THIS ON TO REGULATORY AFFAIRS.CALLBACK CONVERSATION WITH RPTR 692294 REVEALED THE FOLLOWING INFO: THE RPTR WORKED WITH THE CONTRACT TECHNICIAN AT THE STATION TO GET PICTURES; PART NUMBERS AND OTHER INFO ON THE COMPONENT THAT HAD THE FLAG. THE RPTR INDICATED THE COMPONENT WAS IDENTIFIED AS THE AUTO SLAT VALVE ON THE STANDBY HYD MODULE AND THE LOCK AND FLAG WERE REMOVED. THIS FLAG AND VALVE LOCK IS NORMALLY INSTALLED WHEN ENTERING A DOCK FOR HVY MAINT TO PREVENT THE LEADING EDGE DEVICES FROM BEING DEPLOYED; DAMAGING OPEN ENG COWLING. THE PROC IS ON A DOCKING AND DEDUCING JOB CARD AND REQUIRES A SIGNOFF AND IS AN INSPECTOR BUYBACK ITEM. THIS AIRPLANE SOMEHOW GOT OUT OF THE CHK AND ENTERED SVC WHERE IT WAS DISCOVERED IN A NON MAINT STATION. A CONTRACT MAINT TECHNICIAN TESTED THE STANDBY HYD SYSTEM OPERATION AND CHKED OK ANDWAS INSTRUCTED TO SIGN OFF THE CREW LOG RPT. THE FLT CREW DID NOT MAKE A LOG INPUT AND IT APPEARED NO LOG RPT WAS ENTERED. THE RPTR TURNED ALL INFO ON THIS INCIDENT TO THE DEPARTMENT MANAGER.

Data retrieved from NASA's ASRS site as of January 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.