Narrative:

I was instructed to finish an installation of a borrowed part (prsov) on #2 engine. The paperwork had been signed off to the point where a leak check needed to be done. The mechanics that had installed the valve gave me a quick turnover that the valve was installed and the engine 3-WAY valve was placed in ground mode in order to pressurize the system. I had personally pressurized the system while I checked around the v-band clamps that hold the valve in place. I felt no air around the clamps; but did feel a small air blast coming from somewhere on the side of the valve near a small pin (this pin was actually part of the butterfly that stuck out of the valve). I then talked to the mechanics that installed the valve and gave them my results and I was given the notion that it was probably ok. I then talked to the lead on duty and told him what I found. We both thought maybe this pin was some kind of pressure relief. I then reviewed the paperwork which concluded that no leaking was allowed around the clamps. Below this instruction was a note that jet blasts were not allowed; but diffused air was. I thought because I could not feel air around the clamps it was probably ok. I had the system pressurized again to make sure the air was coming from the pin and not the clamps. After this second check; I was pretty sure the air was from the pin; not the clamps. I then reinstalled the slot seal cover and operations checked the thrust reverser with APU bleed air; then put the 3-WAY valve back in flight mode and checked the thrust reverser twice with the engine running. With no defects noted; I signed off the paperwork. The next day the aircraft left and on takeoff got a #2 engine fire warning. The engine was shut down and the aircraft performed an air turn-back. The clamp had not captured both flanges of the tube and the valve. This lead to a great deal of hot bleed air to blow on the fire loop and cause a fire warning. I believe the reasons why this happened are as follows. I was not aware; nor did I make myself aware; that this aircraft had just had this same incident 2 days prior. The mechanics that installed the valve had not opened both of the sides of the slot seal to gain access to the valve. This limited my ability to leak check the clamp or see that it wasn't aligned correctly. The mechanic's turnover did not disclose that they had a hard time getting the valve to line up for clamp installation. I should have used a mirror to check all the way around the clamp for correct installation. I did not research the valve to discover if the pin was supposed to leak. I became complacent in doing my work and should have realized that any air leak in that area could cause a fire warning. To date; I have been investigated by the station manager of maintenance; the station manager of air carrier; and the operations investigator of air carrier. In order to prevent this from happening in the future; I believe that information such as a prior operations event in such a short time period should be passed on to the technician performing the work. A different style of clamp on this valve might also make it easier to see if it has captured both flanges. Callback conversation with reporter revealed the following information: reporter stated he was given a turnover involving the removal of a borrowed blocker valve from another carrier and the installation of his company's own blocker valve on the #2 engine of their B747-200. Reporter stated they were quite surprised to find out the problem was at the v-band clamp attach flange since they had already accomplished a pneumatic leak check using APU bleed air without any major pneumatic air bypassing at the connections.

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Original NASA ASRS Text

Title: MECHANIC REPORTS ON THE EVENTS SURROUNDING AN AIR TURNBACK OF A B747-200 DUE TO A #2 ENGINE FIRE WARNING DURING TAKEOFF. UPPER V-BAND CLAMP WAS NOT PROPERLY SECURED TO A 3-WAY VALVE FLANGE AND BLOCKER VALVE PNEUMATIC DUCTING.

Narrative: I WAS INSTRUCTED TO FINISH AN INSTALLATION OF A BORROWED PART (PRSOV) ON #2 ENG. THE PAPERWORK HAD BEEN SIGNED OFF TO THE POINT WHERE A LEAK CHK NEEDED TO BE DONE. THE MECHS THAT HAD INSTALLED THE VALVE GAVE ME A QUICK TURNOVER THAT THE VALVE WAS INSTALLED AND THE ENG 3-WAY VALVE WAS PLACED IN GND MODE IN ORDER TO PRESSURIZE THE SYS. I HAD PERSONALLY PRESSURIZED THE SYS WHILE I CHKED AROUND THE V-BAND CLAMPS THAT HOLD THE VALVE IN PLACE. I FELT NO AIR AROUND THE CLAMPS; BUT DID FEEL A SMALL AIR BLAST COMING FROM SOMEWHERE ON THE SIDE OF THE VALVE NEAR A SMALL PIN (THIS PIN WAS ACTUALLY PART OF THE BUTTERFLY THAT STUCK OUT OF THE VALVE). I THEN TALKED TO THE MECHS THAT INSTALLED THE VALVE AND GAVE THEM MY RESULTS AND I WAS GIVEN THE NOTION THAT IT WAS PROBABLY OK. I THEN TALKED TO THE LEAD ON DUTY AND TOLD HIM WHAT I FOUND. WE BOTH THOUGHT MAYBE THIS PIN WAS SOME KIND OF PRESSURE RELIEF. I THEN REVIEWED THE PAPERWORK WHICH CONCLUDED THAT NO LEAKING WAS ALLOWED AROUND THE CLAMPS. BELOW THIS INSTRUCTION WAS A NOTE THAT JET BLASTS WERE NOT ALLOWED; BUT DIFFUSED AIR WAS. I THOUGHT BECAUSE I COULD NOT FEEL AIR AROUND THE CLAMPS IT WAS PROBABLY OK. I HAD THE SYS PRESSURIZED AGAIN TO MAKE SURE THE AIR WAS COMING FROM THE PIN AND NOT THE CLAMPS. AFTER THIS SECOND CHK; I WAS PRETTY SURE THE AIR WAS FROM THE PIN; NOT THE CLAMPS. I THEN REINSTALLED THE SLOT SEAL COVER AND OPS CHKED THE THRUST REVERSER WITH APU BLEED AIR; THEN PUT THE 3-WAY VALVE BACK IN FLT MODE AND CHKED THE THRUST REVERSER TWICE WITH THE ENG RUNNING. WITH NO DEFECTS NOTED; I SIGNED OFF THE PAPERWORK. THE NEXT DAY THE ACFT LEFT AND ON TKOF GOT A #2 ENG FIRE WARNING. THE ENG WAS SHUT DOWN AND THE ACFT PERFORMED AN AIR TURN-BACK. THE CLAMP HAD NOT CAPTURED BOTH FLANGES OF THE TUBE AND THE VALVE. THIS LEAD TO A GREAT DEAL OF HOT BLEED AIR TO BLOW ON THE FIRE LOOP AND CAUSE A FIRE WARNING. I BELIEVE THE REASONS WHY THIS HAPPENED ARE AS FOLLOWS. I WAS NOT AWARE; NOR DID I MAKE MYSELF AWARE; THAT THIS ACFT HAD JUST HAD THIS SAME INCIDENT 2 DAYS PRIOR. THE MECHS THAT INSTALLED THE VALVE HAD NOT OPENED BOTH OF THE SIDES OF THE SLOT SEAL TO GAIN ACCESS TO THE VALVE. THIS LIMITED MY ABILITY TO LEAK CHK THE CLAMP OR SEE THAT IT WASN'T ALIGNED CORRECTLY. THE MECH'S TURNOVER DID NOT DISCLOSE THAT THEY HAD A HARD TIME GETTING THE VALVE TO LINE UP FOR CLAMP INSTALLATION. I SHOULD HAVE USED A MIRROR TO CHK ALL THE WAY AROUND THE CLAMP FOR CORRECT INSTALLATION. I DID NOT RESEARCH THE VALVE TO DISCOVER IF THE PIN WAS SUPPOSED TO LEAK. I BECAME COMPLACENT IN DOING MY WORK AND SHOULD HAVE REALIZED THAT ANY AIR LEAK IN THAT AREA COULD CAUSE A FIRE WARNING. TO DATE; I HAVE BEEN INVESTIGATED BY THE STATION MGR OF MAINT; THE STATION MGR OF ACR; AND THE OPS INVESTIGATOR OF ACR. IN ORDER TO PREVENT THIS FROM HAPPENING IN THE FUTURE; I BELIEVE THAT INFO SUCH AS A PRIOR OPS EVENT IN SUCH A SHORT TIME PERIOD SHOULD BE PASSED ON TO THE TECHNICIAN PERFORMING THE WORK. A DIFFERENT STYLE OF CLAMP ON THIS VALVE MIGHT ALSO MAKE IT EASIER TO SEE IF IT HAS CAPTURED BOTH FLANGES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED HE WAS GIVEN A TURNOVER INVOLVING THE REMOVAL OF A BORROWED BLOCKER VALVE FROM ANOTHER CARRIER AND THE INSTALLATION OF HIS COMPANY'S OWN BLOCKER VALVE ON THE #2 ENGINE OF THEIR B747-200. REPORTER STATED THEY WERE QUITE SURPRISED TO FIND OUT THE PROBLEM WAS AT THE V-BAND CLAMP ATTACH FLANGE SINCE THEY HAD ALREADY ACCOMPLISHED A PNEUMATIC LEAK CHECK USING APU BLEED AIR WITHOUT ANY MAJOR PNEUMATIC AIR BYPASSING AT THE CONNECTIONS.

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