Narrative:

While in the process of doing his weekly check a mechanic reported to me that there was fuel leaking out of the mid-engine drain lines. The fuel was coming out of the #4 drain tube. The mechanic performed the isolation procedure called out for in the manual and determined that the source of the leak was the hpt control valve. I notified air carrier maintenance control technician desk about the fuel leak, and that it was about 60 drops a min which is at the serviceable limit as per maintenance manual 71-71-00 page 608. The mechanic working the aircraft requested that we run the engine at a higher power setting, so the aircraft was taken out to the run-up area and run for a 2ND time. The mechanic reported that he was getting 64 drops per min. The aircraft returned to the gate and maintenance control was notified. I asked maintenance control which limits do you use, as the manual was not too clear on the power settings. I asked them (maintenance control) to call power plant engineering technical desk. They did and it was relayed to me by maintenance control that power plant engineering said: the proper procedure was to run the engine at idle, count the drops and then shut down the engine and count the drops when the engine stops spinning. We performed this procedure and when we did, I counted the drops myself using a stop watch feature on a wrist watch to be as accurate as I could be. I counted 52 drops per min of idle and when the engine was shut down I counted 18 drops per min. This was found to be within the serviceable limits of maintenance manual 71-71-00 page 608. I released the aircraft and programmed the hpt control valve to be replaced in charlotte, clt, next maintenance layover. I found the maintenance manual of this reference very imprecise and leaving a lot up to judgement. Because I was dealing with a total of 6 aircraft and 8 or 9 mechanics I was not examining the maintenance manual as closely as I should have been and relying too much on the verbal information from maintenance control.

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Original NASA ASRS Text

Title: A B737-400 HAD CONFLICTING AND CONFUSING MAINT MANUAL PROCS ON DETERMINING THE ALLOWABLE FUEL LEAK LIMITS ON THE TURBINE CLRNC CTL VALVE.

Narrative: WHILE IN THE PROCESS OF DOING HIS WEEKLY CHK A MECH RPTED TO ME THAT THERE WAS FUEL LEAKING OUT OF THE MID-ENG DRAIN LINES. THE FUEL WAS COMING OUT OF THE #4 DRAIN TUBE. THE MECH PERFORMED THE ISOLATION PROC CALLED OUT FOR IN THE MANUAL AND DETERMINED THAT THE SOURCE OF THE LEAK WAS THE HPT CTL VALVE. I NOTIFIED ACR MAINT CTL TECHNICIAN DESK ABOUT THE FUEL LEAK, AND THAT IT WAS ABOUT 60 DROPS A MIN WHICH IS AT THE SERVICEABLE LIMIT AS PER MAINT MANUAL 71-71-00 PAGE 608. THE MECH WORKING THE ACFT REQUESTED THAT WE RUN THE ENG AT A HIGHER PWR SETTING, SO THE ACFT WAS TAKEN OUT TO THE RUN-UP AREA AND RUN FOR A 2ND TIME. THE MECH RPTED THAT HE WAS GETTING 64 DROPS PER MIN. THE ACFT RETURNED TO THE GATE AND MAINT CTL WAS NOTIFIED. I ASKED MAINT CTL WHICH LIMITS DO YOU USE, AS THE MANUAL WAS NOT TOO CLR ON THE PWR SETTINGS. I ASKED THEM (MAINT CTL) TO CALL PWR PLANT ENGINEERING TECHNICAL DESK. THEY DID AND IT WAS RELAYED TO ME BY MAINT CTL THAT PWR PLANT ENGINEERING SAID: THE PROPER PROC WAS TO RUN THE ENG AT IDLE, COUNT THE DROPS AND THEN SHUT DOWN THE ENG AND COUNT THE DROPS WHEN THE ENG STOPS SPINNING. WE PERFORMED THIS PROC AND WHEN WE DID, I COUNTED THE DROPS MYSELF USING A STOP WATCH FEATURE ON A WRIST WATCH TO BE AS ACCURATE AS I COULD BE. I COUNTED 52 DROPS PER MIN OF IDLE AND WHEN THE ENG WAS SHUT DOWN I COUNTED 18 DROPS PER MIN. THIS WAS FOUND TO BE WITHIN THE SERVICEABLE LIMITS OF MAINT MANUAL 71-71-00 PAGE 608. I RELEASED THE ACFT AND PROGRAMMED THE HPT CTL VALVE TO BE REPLACED IN CHARLOTTE, CLT, NEXT MAINT LAYOVER. I FOUND THE MAINT MANUAL OF THIS REF VERY IMPRECISE AND LEAVING A LOT UP TO JUDGEMENT. BECAUSE I WAS DEALING WITH A TOTAL OF 6 ACFT AND 8 OR 9 MECHS I WAS NOT EXAMINING THE MAINT MANUAL AS CLOSELY AS I SHOULD HAVE BEEN AND RELYING TOO MUCH ON THE VERBAL INFO FROM MAINT CTL.

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.