Narrative:

On jul/fri/2004, I was assigned with two other mechanics to replace the nose landing gear strut seals on aircraft X. We disassembled the nose gear strut and replaced all the seals. We then reassembled the nose gear assembly. During the disassembly, we indexed the cylinder to a lug at the top of the piston. The upper cam is held in position to the cylinder with eight pins. The upper cam did not get indexed because it is hidden by the pin retainer bush. On reassembly, this upper cam was installed one hole off. After the strut was reassembled, we went to lunch. Another crew serviced the strut and returned the jacking equipment. As a result, we did not do a gear retraction test. The aircraft departed ZZZ and could not retract the gear. The aircraft returned to ZZZ where the strut was disassembled and the misalignment of the upper cam was found. I feel that contributing factors to this incident were the manner in which the maintenance manual is written. Airbus has written the manual so that different effectivity of aircraft are intermixed, parts labeled with an item number on one page have a different item number on the next page. And the procedure for removing the upper cam is at the end of the maintenance manual, after the installation of the shock absorber assembly. Airbus does have a note about maintaining the alignment of the cam, however, simply having one dowel pin hole larger or moved to a different position would have indexed the cam to be only installed correctly. Currently, the inspection list does not cover a seal change on the gear. Since the gear did not retract due to the mis-position of the cam I suggest it be added to the inspection list. Supplemental information from acn 623274: this part of the paperwork was very difficult to understand so other mechanics helped in reading and rereading the paperwork. Supplemental information from acn 623126: the aircraft departed ZZZ and the nose gear failed to retract. After it returned to the field, it was discovered that the nose gear was not centering. After disassembly of the nose gear strut, it was discovered that the centering cam had been installed incorrectly. After looking at the complete installation, I found that the nose gear centering cam can be installed in 8 different positions. Supplemental information from acn 622987: I was assigned to fix a nose landing gear leak on aircraft X. I disassembled the strut. I then cleaned and inspected all components. I installed new seals and then reassembled the strut assembly. Another crew serviced the strut with fluid. A gear retraction was not accomplished. On the first flight, the nose landing gear would not retract. I was later informed that the upper cam was assembled with one hole off. The landing gear control interface units also failed during testing. By having 8 holes in this cam assembly it gives you 7 ways to make a mistake. Under the inspection it is not necessary to have this inspected. Callback conversation with reporter from acn 622988 revealed the following information: the reporter stated the airbus maintenance manual procedure for changing the strut seals is complex as it gives airplane effectivity pictorials with part numbers that change from pictorial to pictorial. The reporter said with experienced technicians that have changed strut seals from domestic and foreign aircraft all agree this strut seal procedure is really poor. The reporter stated the required gear swing was not accomplished and would have revealed the nose gear was not centered.

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Original NASA ASRS Text

Title: AN A320 WAS RELEASED FOR SERVICE AFTER A NOSE STRUT SEAL CHANGE. DURING FIRST FLT NOSE GEAR FAILED TO RETRACT. FOUND NOSE CENTERING CAM INDEXED INCORRECTLY.

Narrative: ON JUL/FRI/2004, I WAS ASSIGNED WITH TWO OTHER MECHANICS TO REPLACE THE NOSE LANDING GEAR STRUT SEALS ON ACFT X. WE DISASSEMBLED THE NOSE GEAR STRUT AND REPLACED ALL THE SEALS. WE THEN REASSEMBLED THE NOSE GEAR ASSEMBLY. DURING THE DISASSEMBLY, WE INDEXED THE CYLINDER TO A LUG AT THE TOP OF THE PISTON. THE UPPER CAM IS HELD IN POSITION TO THE CYLINDER WITH EIGHT PINS. THE UPPER CAM DID NOT GET INDEXED BECAUSE IT IS HIDDEN BY THE PIN RETAINER BUSH. ON REASSEMBLY, THIS UPPER CAM WAS INSTALLED ONE HOLE OFF. AFTER THE STRUT WAS REASSEMBLED, WE WENT TO LUNCH. ANOTHER CREW SERVICED THE STRUT AND RETURNED THE JACKING EQUIPMENT. AS A RESULT, WE DID NOT DO A GEAR RETRACTION TEST. THE ACFT DEPARTED ZZZ AND COULD NOT RETRACT THE GEAR. THE ACFT RETURNED TO ZZZ WHERE THE STRUT WAS DISASSEMBLED AND THE MISALIGNMENT OF THE UPPER CAM WAS FOUND. I FEEL THAT CONTRIBUTING FACTORS TO THIS INCIDENT WERE THE MANNER IN WHICH THE MAINT MANUAL IS WRITTEN. AIRBUS HAS WRITTEN THE MANUAL SO THAT DIFFERENT EFFECTIVITY OF ACFT ARE INTERMIXED, PARTS LABELED WITH AN ITEM NUMBER ON ONE PAGE HAVE A DIFFERENT ITEM NUMBER ON THE NEXT PAGE. AND THE PROC FOR REMOVING THE UPPER CAM IS AT THE END OF THE MAINT MANUAL, AFTER THE INSTALLATION OF THE SHOCK ABSORBER ASSEMBLY. AIRBUS DOES HAVE A NOTE ABOUT MAINTAINING THE ALIGNMENT OF THE CAM, HOWEVER, SIMPLY HAVING ONE DOWEL PIN HOLE LARGER OR MOVED TO A DIFFERENT POSITION WOULD HAVE INDEXED THE CAM TO BE ONLY INSTALLED CORRECTLY. CURRENTLY, THE INSPECTION LIST DOES NOT COVER A SEAL CHANGE ON THE GEAR. SINCE THE GEAR DID NOT RETRACT DUE TO THE MIS-POSITION OF THE CAM I SUGGEST IT BE ADDED TO THE INSPECTION LIST. SUPPLEMENTAL INFO FROM ACN 623274: THIS PART OF THE PAPERWORK WAS VERY DIFFICULT TO UNDERSTAND SO OTHER MECHANICS HELPED IN READING AND REREADING THE PAPERWORK. SUPPLEMENTAL INFO FROM ACN 623126: THE ACFT DEPARTED ZZZ AND THE NOSE GEAR FAILED TO RETRACT. AFTER IT RETURNED TO THE FIELD, IT WAS DISCOVERED THAT THE NOSE GEAR WAS NOT CENTERING. AFTER DISASSEMBLY OF THE NOSE GEAR STRUT, IT WAS DISCOVERED THAT THE CENTERING CAM HAD BEEN INSTALLED INCORRECTLY. AFTER LOOKING AT THE COMPLETE INSTALLATION, I FOUND THAT THE NOSE GEAR CENTERING CAM CAN BE INSTALLED IN 8 DIFFERENT POSITIONS. SUPPLEMENTAL INFO FROM ACN 622987: I WAS ASSIGNED TO FIX A NOSE LANDING GEAR LEAK ON ACFT X. I DISASSEMBLED THE STRUT. I THEN CLEANED AND INSPECTED ALL COMPONENTS. I INSTALLED NEW SEALS AND THEN REASSEMBLED THE STRUT ASSEMBLY. ANOTHER CREW SERVICED THE STRUT WITH FLUID. A GEAR RETRACTION WAS NOT ACCOMPLISHED. ON THE FIRST FLT, THE NOSE LANDING GEAR WOULD NOT RETRACT. I WAS LATER INFORMED THAT THE UPPER CAM WAS ASSEMBLED WITH ONE HOLE OFF. THE LNDG GEAR CTL INTERFACE UNITS ALSO FAILED DURING TESTING. BY HAVING 8 HOLES IN THIS CAM ASSEMBLY IT GIVES YOU 7 WAYS TO MAKE A MISTAKE. UNDER THE INSPECTION IT IS NOT NECESSARY TO HAVE THIS INSPECTED. CALLBACK CONVERSATION WITH RPTR FROM ACN 622988 REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRBUS MAINT MANUAL PROC FOR CHANGING THE STRUT SEALS IS COMPLEX AS IT GIVES AIRPLANE EFFECTIVITY PICTORIALS WITH PART NUMBERS THAT CHANGE FROM PICTORIAL TO PICTORIAL. THE RPTR SAID WITH EXPERIENCED TECHNICIANS THAT HAVE CHANGED STRUT SEALS FROM DOMESTIC AND FOREIGN ACFT ALL AGREE THIS STRUT SEAL PROC IS REALLY POOR. THE RPTR STATED THE REQUIRED GEAR SWING WAS NOT ACCOMPLISHED AND WOULD HAVE REVEALED THE NOSE GEAR WAS NOT CENTERED.

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.